/*
 * super.c - NTFS kernel super block handling. Part of the Linux-NTFS project.
 *
 * Copyright (c) 2001-2007 Anton Altaparmakov
 * Copyright (c) 2001,2002 Richard Russon
 *
 * This program/include file is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program/include file is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program (in the main directory of the Linux-NTFS
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/stddef.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/blkdev.h>       /* For bdev_hardsect_size(). */
#include <linux/backing-dev.h>
#include <linux/buffer_head.h>
#include <linux/vfs.h>
#include <linux/moduleparam.h>
#include <linux/smp_lock.h>

#include "sysctl.h"
#include "logfile.h"
#include "quota.h"
#include "usnjrnl.h"
#include "dir.h"
#include "debug.h"
#include "index.h"
#include "aops.h"
#include "layout.h"
#include "malloc.h"
#include "ntfs.h"

/* Number of mounted filesystems which have compression enabled. */
static unsigned long ntfs_nr_compression_users;

/* A global default upcase table and a corresponding reference count. */
static ntfschar *default_upcase = NULL;
static unsigned long ntfs_nr_upcase_users = 0;

/* Error constants/strings used in inode.c::ntfs_show_options(). */
typedef enum {
        /* One of these must be present, default is ON_ERRORS_CONTINUE. */
        ON_ERRORS_PANIC                 = 0x01,
        ON_ERRORS_REMOUNT_RO            = 0x02,
        ON_ERRORS_CONTINUE              = 0x04,
        /* Optional, can be combined with any of the above. */
        ON_ERRORS_RECOVER               = 0x10,
} ON_ERRORS_ACTIONS;

const option_t on_errors_arr[] = {
        { ON_ERRORS_PANIC,      "panic" },
        { ON_ERRORS_REMOUNT_RO, "remount-ro", },
        { ON_ERRORS_CONTINUE,   "continue", },
        { ON_ERRORS_RECOVER,    "recover" },
        { 0,                    NULL }
};

/**
 * simple_getbool -
 *
 * Copied from old ntfs driver (which copied from vfat driver).
 */
static int simple_getbool(char *s, bool *setval)
{
        if (s) {
                if (!strcmp(s, "1") || !strcmp(s, "yes") || !strcmp(s, "true"))
                        *setval = true;
                else if (!strcmp(s, "0") || !strcmp(s, "no") ||
                                                        !strcmp(s, "false"))
                        *setval = false;
                else
                        return 0;
        } else
                *setval = true;
        return 1;
}

/**
 * parse_options - parse the (re)mount options
 * @vol:        ntfs volume
 * @opt:        string containing the (re)mount options
 *
 * Parse the recognized options in @opt for the ntfs volume described by @vol.
 */
static bool parse_options(ntfs_volume *vol, char *opt)
{
        char *p, *v, *ov;
        static char *utf8 = "utf8";
        int errors = 0, sloppy = 0;
        uid_t uid = (uid_t)-1;
        gid_t gid = (gid_t)-1;
        mode_t fmask = (mode_t)-1, dmask = (mode_t)-1;
        int mft_zone_multiplier = -1, on_errors = -1;
        int show_sys_files = -1, case_sensitive = -1, disable_sparse = -1;
        struct nls_table *nls_map = NULL, *old_nls;

        /* I am lazy... (-8 */
#define NTFS_GETOPT_WITH_DEFAULT(option, variable, default_value)       \
        if (!strcmp(p, option)) {                                       \
                if (!v || !*v)                                          \
                        variable = default_value;                       \
                else {                                                  \
                        variable = simple_strtoul(ov = v, &v, 0);       \
                        if (*v)                                         \
                                goto needs_val;                         \
                }                                                       \
        }
#define NTFS_GETOPT(option, variable)                                   \
        if (!strcmp(p, option)) {                                       \
                if (!v || !*v)                                          \
                        goto needs_arg;                                 \
                variable = simple_strtoul(ov = v, &v, 0);               \
                if (*v)                                                 \
                        goto needs_val;                                 \
        }
#define NTFS_GETOPT_OCTAL(option, variable)                             \
        if (!strcmp(p, option)) {                                       \
                if (!v || !*v)                                          \
                        goto needs_arg;                                 \
                variable = simple_strtoul(ov = v, &v, 8);               \
                if (*v)                                                 \
                        goto needs_val;                                 \
        }
#define NTFS_GETOPT_BOOL(option, variable)                              \
        if (!strcmp(p, option)) {                                       \
                bool val;                                               \
                if (!simple_getbool(v, &val))                           \
                        goto needs_bool;                                \
                variable = val;                                         \
        }
#define NTFS_GETOPT_OPTIONS_ARRAY(option, variable, opt_array)          \
        if (!strcmp(p, option)) {                                       \
                int _i;                                                 \
                if (!v || !*v)                                          \
                        goto needs_arg;                                 \
                ov = v;                                                 \
                if (variable == -1)                                     \
                        variable = 0;                                   \
                for (_i = 0; opt_array[_i].str && *opt_array[_i].str; _i++) \
                        if (!strcmp(opt_array[_i].str, v)) {            \
                                variable |= opt_array[_i].val;          \
                                break;                                  \
                        }                                               \
                if (!opt_array[_i].str || !*opt_array[_i].str)          \
                        goto needs_val;                                 \
        }
        if (!opt || !*opt)
                goto no_mount_options;
        ntfs_debug("Entering with mount options string: %s", opt);
        while ((p = strsep(&opt, ","))) {
                if ((v = strchr(p, '=')))
                        *v++ = 0;
                NTFS_GETOPT("uid", uid)
                else NTFS_GETOPT("gid", gid)
                else NTFS_GETOPT_OCTAL("umask", fmask = dmask)
                else NTFS_GETOPT_OCTAL("fmask", fmask)
                else NTFS_GETOPT_OCTAL("dmask", dmask)
                else NTFS_GETOPT("mft_zone_multiplier", mft_zone_multiplier)
                else NTFS_GETOPT_WITH_DEFAULT("sloppy", sloppy, true)
                else NTFS_GETOPT_BOOL("show_sys_files", show_sys_files)
                else NTFS_GETOPT_BOOL("case_sensitive", case_sensitive)
                else NTFS_GETOPT_BOOL("disable_sparse", disable_sparse)
                else NTFS_GETOPT_OPTIONS_ARRAY("errors", on_errors,
                                on_errors_arr)
                else if (!strcmp(p, "posix") || !strcmp(p, "show_inodes"))
                        ntfs_warning(vol->sb, "Ignoring obsolete option %s.",
                                        p);
                else if (!strcmp(p, "nls") || !strcmp(p, "iocharset")) {
                        if (!strcmp(p, "iocharset"))
                                ntfs_warning(vol->sb, "Option iocharset is "
                                                "deprecated. Please use "
                                                "option nls=<charsetname> in "
                                                "the future.");
                        if (!v || !*v)
                                goto needs_arg;
use_utf8:
                        old_nls = nls_map;
                        nls_map = load_nls(v);
                        if (!nls_map) {
                                if (!old_nls) {
                                        ntfs_error(vol->sb, "NLS character set "
                                                        "%s not found.", v);
                                        return false;
                                }
                                ntfs_error(vol->sb, "NLS character set %s not "
                                                "found. Using previous one %s.",
                                                v, old_nls->charset);
                                nls_map = old_nls;
                        } else /* nls_map */ {
                                if (old_nls)
                                        unload_nls(old_nls);
                        }
                } else if (!strcmp(p, "utf8")) {
                        bool val = false;
                        ntfs_warning(vol->sb, "Option utf8 is no longer "
                                   "supported, using option nls=utf8. Please "
                                   "use option nls=utf8 in the future and "
                                   "make sure utf8 is compiled either as a "
                                   "module or into the kernel.");
                        if (!v || !*v)
                                val = true;
                        else if (!simple_getbool(v, &val))
                                goto needs_bool;
                        if (val) {
                                v = utf8;
                                goto use_utf8;
                        }
                } else {
                        ntfs_error(vol->sb, "Unrecognized mount option %s.", p);
                        if (errors < INT_MAX)
                                errors++;
                }
#undef NTFS_GETOPT_OPTIONS_ARRAY
#undef NTFS_GETOPT_BOOL
#undef NTFS_GETOPT
#undef NTFS_GETOPT_WITH_DEFAULT
        }
no_mount_options:
        if (errors && !sloppy)
                return false;
        if (sloppy)
                ntfs_warning(vol->sb, "Sloppy option given. Ignoring "
                                "unrecognized mount option(s) and continuing.");
        /* Keep this first! */
        if (on_errors != -1) {
                if (!on_errors) {
                        ntfs_error(vol->sb, "Invalid errors option argument "
                                        "or bug in options parser.");
                        return false;
                }
        }
        if (nls_map) {
                if (vol->nls_map && vol->nls_map != nls_map) {
                        ntfs_error(vol->sb, "Cannot change NLS character set "
                                        "on remount.");
                        return false;
                } /* else (!vol->nls_map) */
                ntfs_debug("Using NLS character set %s.", nls_map->charset);
                vol->nls_map = nls_map;
        } else /* (!nls_map) */ {
                if (!vol->nls_map) {
                        vol->nls_map = load_nls_default();
                        if (!vol->nls_map) {
                                ntfs_error(vol->sb, "Failed to load default "
                                                "NLS character set.");
                                return false;
                        }
                        ntfs_debug("Using default NLS character set (%s).",
                                        vol->nls_map->charset);
                }
        }
        if (mft_zone_multiplier != -1) {
                if (vol->mft_zone_multiplier && vol->mft_zone_multiplier !=
                                mft_zone_multiplier) {
                        ntfs_error(vol->sb, "Cannot change mft_zone_multiplier "
                                        "on remount.");
                        return false;
                }
                if (mft_zone_multiplier < 1 || mft_zone_multiplier > 4) {
                        ntfs_error(vol->sb, "Invalid mft_zone_multiplier. "
                                        "Using default value, i.e. 1.");
                        mft_zone_multiplier = 1;
                }
                vol->mft_zone_multiplier = mft_zone_multiplier;
        }
        if (!vol->mft_zone_multiplier)
                vol->mft_zone_multiplier = 1;
        if (on_errors != -1)
                vol->on_errors = on_errors;
        if (!vol->on_errors || vol->on_errors == ON_ERRORS_RECOVER)
                vol->on_errors |= ON_ERRORS_CONTINUE;
        if (uid != (uid_t)-1)
                vol->uid = uid;
        if (gid != (gid_t)-1)
                vol->gid = gid;
        if (fmask != (mode_t)-1)
                vol->fmask = fmask;
        if (dmask != (mode_t)-1)
                vol->dmask = dmask;
        if (show_sys_files != -1) {
                if (show_sys_files)
                        NVolSetShowSystemFiles(vol);
                else
                        NVolClearShowSystemFiles(vol);
        }
        if (case_sensitive != -1) {
                if (case_sensitive)
                        NVolSetCaseSensitive(vol);
                else
                        NVolClearCaseSensitive(vol);
        }
        if (disable_sparse != -1) {
                if (disable_sparse)
                        NVolClearSparseEnabled(vol);
                else {
                        if (!NVolSparseEnabled(vol) &&
                                        vol->major_ver && vol->major_ver < 3)
                                ntfs_warning(vol->sb, "Not enabling sparse "
                                                "support due to NTFS volume "
                                                "version %i.%i (need at least "
                                                "version 3.0).", vol->major_ver,
                                                vol->minor_ver);
                        else
                                NVolSetSparseEnabled(vol);
                }
        }
        return true;
needs_arg:
        ntfs_error(vol->sb, "The %s option requires an argument.", p);
        return false;
needs_bool:
        ntfs_error(vol->sb, "The %s option requires a boolean argument.", p);
        return false;
needs_val:
        ntfs_error(vol->sb, "Invalid %s option argument: %s", p, ov);
        return false;
}

#ifdef NTFS_RW

/**
 * ntfs_write_volume_flags - write new flags to the volume information flags
 * @vol:        ntfs volume on which to modify the flags
 * @flags:      new flags value for the volume information flags
 *
 * Internal function.  You probably want to use ntfs_{set,clear}_volume_flags()
 * instead (see below).
 *
 * Replace the volume information flags on the volume @vol with the value
 * supplied in @flags.  Note, this overwrites the volume information flags, so
 * make sure to combine the flags you want to modify with the old flags and use
 * the result when calling ntfs_write_volume_flags().
 *
 * Return 0 on success and -errno on error.
 */
static int ntfs_write_volume_flags(ntfs_volume *vol, const VOLUME_FLAGS flags)
{
        ntfs_inode *ni = NTFS_I(vol->vol_ino);
        MFT_RECORD *m;
        VOLUME_INFORMATION *vi;
        ntfs_attr_search_ctx *ctx;
        int err;

        ntfs_debug("Entering, old flags = 0x%x, new flags = 0x%x.",
                        le16_to_cpu(vol->vol_flags), le16_to_cpu(flags));
        if (vol->vol_flags == flags)
                goto done;
        BUG_ON(!ni);
        m = map_mft_record(ni);
        if (IS_ERR(m)) {
                err = PTR_ERR(m);
                goto err_out;
        }
        ctx = ntfs_attr_get_search_ctx(ni, m);
        if (!ctx) {
                err = -ENOMEM;
                goto put_unm_err_out;
        }
        err = ntfs_attr_lookup(AT_VOLUME_INFORMATION, NULL, 0, 0, 0, NULL, 0,
                        ctx);
        if (err)
                goto put_unm_err_out;
        vi = (VOLUME_INFORMATION*)((u8*)ctx->attr +
                        le16_to_cpu(ctx->attr->data.resident.value_offset));
        vol->vol_flags = vi->flags = flags;
        flush_dcache_mft_record_page(ctx->ntfs_ino);
        mark_mft_record_dirty(ctx->ntfs_ino);
        ntfs_attr_put_search_ctx(ctx);
        unmap_mft_record(ni);
done:
        ntfs_debug("Done.");
        return 0;
put_unm_err_out:
        if (ctx)
                ntfs_attr_put_search_ctx(ctx);
        unmap_mft_record(ni);
err_out:
        ntfs_error(vol->sb, "Failed with error code %i.", -err);
        return err;
}

/**
 * ntfs_set_volume_flags - set bits in the volume information flags
 * @vol:        ntfs volume on which to modify the flags
 * @flags:      flags to set on the volume
 *
 * Set the bits in @flags in the volume information flags on the volume @vol.
 *
 * Return 0 on success and -errno on error.
 */
static inline int ntfs_set_volume_flags(ntfs_volume *vol, VOLUME_FLAGS flags)
{
        flags &= VOLUME_FLAGS_MASK;
        return ntfs_write_volume_flags(vol, vol->vol_flags | flags);
}

/**
 * ntfs_clear_volume_flags - clear bits in the volume information flags
 * @vol:        ntfs volume on which to modify the flags
 * @flags:      flags to clear on the volume
 *
 * Clear the bits in @flags in the volume information flags on the volume @vol.
 *
 * Return 0 on success and -errno on error.
 */
static inline int ntfs_clear_volume_flags(ntfs_volume *vol, VOLUME_FLAGS flags)
{
        flags &= VOLUME_FLAGS_MASK;
        flags = vol->vol_flags & cpu_to_le16(~le16_to_cpu(flags));
        return ntfs_write_volume_flags(vol, flags);
}

#endif /* NTFS_RW */

/**
 * ntfs_remount - change the mount options of a mounted ntfs filesystem
 * @sb:         superblock of mounted ntfs filesystem
 * @flags:      remount flags
 * @opt:        remount options string
 *
 * Change the mount options of an already mounted ntfs filesystem.
 *
 * NOTE:  The VFS sets the @sb->s_flags remount flags to @flags after
 * ntfs_remount() returns successfully (i.e. returns 0).  Otherwise,
 * @sb->s_flags are not changed.
 */
static int ntfs_remount(struct super_block *sb, int *flags, char *opt)
{
        ntfs_volume *vol = NTFS_SB(sb);

        ntfs_debug("Entering with remount options string: %s", opt);
#ifndef NTFS_RW
        /* For read-only compiled driver, enforce read-only flag. */
        *flags |= MS_RDONLY;
#else /* NTFS_RW */
        /*
         * For the read-write compiled driver, if we are remounting read-write,
         * make sure there are no volume errors and that no unsupported volume
         * flags are set.  Also, empty the logfile journal as it would become
         * stale as soon as something is written to the volume and mark the
         * volume dirty so that chkdsk is run if the volume is not umounted
         * cleanly.  Finally, mark the quotas out of date so Windows rescans
         * the volume on boot and updates them.
         *
         * When remounting read-only, mark the volume clean if no volume errors
         * have occured.
         */
        if ((sb->s_flags & MS_RDONLY) && !(*flags & MS_RDONLY)) {
                static const char *es = ".  Cannot remount read-write.";

                /* Remounting read-write. */
                if (NVolErrors(vol)) {
                        ntfs_error(sb, "Volume has errors and is read-only%s",
                                        es);
                        return -EROFS;
                }
                if (vol->vol_flags & VOLUME_IS_DIRTY) {
                        ntfs_error(sb, "Volume is dirty and read-only%s", es);
                        return -EROFS;
                }
                if (vol->vol_flags & VOLUME_MODIFIED_BY_CHKDSK) {
                        ntfs_error(sb, "Volume has been modified by chkdsk "
                                        "and is read-only%s", es);
                        return -EROFS;
                }
                if (vol->vol_flags & VOLUME_MUST_MOUNT_RO_MASK) {
                        ntfs_error(sb, "Volume has unsupported flags set "
                                        "(0x%x) and is read-only%s",
                                        (unsigned)le16_to_cpu(vol->vol_flags),
                                        es);
                        return -EROFS;
                }
                if (ntfs_set_volume_flags(vol, VOLUME_IS_DIRTY)) {
                        ntfs_error(sb, "Failed to set dirty bit in volume "
                                        "information flags%s", es);
                        return -EROFS;
                }
#if 0
                // TODO: Enable this code once we start modifying anything that
                //       is different between NTFS 1.2 and 3.x...
                /* Set NT4 compatibility flag on newer NTFS version volumes. */
                if ((vol->major_ver > 1)) {
                        if (ntfs_set_volume_flags(vol, VOLUME_MOUNTED_ON_NT4)) {
                                ntfs_error(sb, "Failed to set NT4 "
                                                "compatibility flag%s", es);
                                NVolSetErrors(vol);
                                return -EROFS;
                        }
                }
#endif
                if (!ntfs_empty_logfile(vol->logfile_ino)) {
                        ntfs_error(sb, "Failed to empty journal $LogFile%s",
                                        es);
                        NVolSetErrors(vol);
                        return -EROFS;
                }
                if (!ntfs_mark_quotas_out_of_date(vol)) {
                        ntfs_error(sb, "Failed to mark quotas out of date%s",
                                        es);
                        NVolSetErrors(vol);
                        return -EROFS;
                }
                if (!ntfs_stamp_usnjrnl(vol)) {
                        ntfs_error(sb, "Failed to stamp transation log "
                                        "($UsnJrnl)%s", es);
                        NVolSetErrors(vol);
                        return -EROFS;
                }
        } else if (!(sb->s_flags & MS_RDONLY) && (*flags & MS_RDONLY)) {
                /* Remounting read-only. */
                if (!NVolErrors(vol)) {
                        if (ntfs_clear_volume_flags(vol, VOLUME_IS_DIRTY))
                                ntfs_warning(sb, "Failed to clear dirty bit "
                                                "in volume information "
                                                "flags.  Run chkdsk.");
                }
        }
#endif /* NTFS_RW */

        // TODO: Deal with *flags.

        if (!parse_options(vol, opt))
                return -EINVAL;
        ntfs_debug("Done.");
        return 0;
}

/**
 * is_boot_sector_ntfs - check whether a boot sector is a valid NTFS boot sector
 * @sb:         Super block of the device to which @b belongs.
 * @b:          Boot sector of device @sb to check.
 * @silent:     If 'true', all output will be silenced.
 *
 * is_boot_sector_ntfs() checks whether the boot sector @b is a valid NTFS boot
 * sector. Returns 'true' if it is valid and 'false' if not.
 *
 * @sb is only needed for warning/error output, i.e. it can be NULL when silent
 * is 'true'.
 */
static bool is_boot_sector_ntfs(const struct super_block *sb,
                const NTFS_BOOT_SECTOR *b, const bool silent)
{
        /*
         * Check that checksum == sum of u32 values from b to the checksum
         * field.  If checksum is zero, no checking is done.  We will work when
         * the checksum test fails, since some utilities update the boot sector
         * ignoring the checksum which leaves the checksum out-of-date.  We
         * report a warning if this is the case.
         */
        if ((void*)b < (void*)&b->checksum && b->checksum && !silent) {
                le32 *u;
                u32 i;

                for (i = 0, u = (le32*)b; u < (le32*)(&b->checksum); ++u)
                        i += le32_to_cpup(u);
                if (le32_to_cpu(b->checksum) != i)
                        ntfs_warning(sb, "Invalid boot sector checksum.");
        }
        /* Check OEMidentifier is "NTFS    " */
        if (b->oem_id != magicNTFS)
                goto not_ntfs;
        /* Check bytes per sector value is between 256 and 4096. */
        if (le16_to_cpu(b->bpb.bytes_per_sector) < 0x100 ||
                        le16_to_cpu(b->bpb.bytes_per_sector) > 0x1000)
                goto not_ntfs;
        /* Check sectors per cluster value is valid. */
        switch (b->bpb.sectors_per_cluster) {
        case 1: case 2: case 4: case 8: case 16: case 32: case 64: case 128:
                break;
        default:
                goto not_ntfs;
        }
        /* Check the cluster size is not above the maximum (64kiB). */
        if ((u32)le16_to_cpu(b->bpb.bytes_per_sector) *
                        b->bpb.sectors_per_cluster > NTFS_MAX_CLUSTER_SIZE)
                goto not_ntfs;
        /* Check reserved/unused fields are really zero. */
        if (le16_to_cpu(b->bpb.reserved_sectors) ||
                        le16_to_cpu(b->bpb.root_entries) ||
                        le16_to_cpu(b->bpb.sectors) ||
                        le16_to_cpu(b->bpb.sectors_per_fat) ||
                        le32_to_cpu(b->bpb.large_sectors) || b->bpb.fats)
                goto not_ntfs;
        /* Check clusters per file mft record value is valid. */
        if ((u8)b->clusters_per_mft_record < 0xe1 ||
                        (u8)b->clusters_per_mft_record > 0xf7)
                switch (b->clusters_per_mft_record) {
                case 1: case 2: case 4: case 8: case 16: case 32: case 64:
                        break;
                default:
                        goto not_ntfs;
                }
        /* Check clusters per index block value is valid. */
        if ((u8)b->clusters_per_index_record < 0xe1 ||
                        (u8)b->clusters_per_index_record > 0xf7)
                switch (b->clusters_per_index_record) {
                case 1: case 2: case 4: case 8: case 16: case 32: case 64:
                        break;
                default:
                        goto not_ntfs;
                }
        /*
         * Check for valid end of sector marker. We will work without it, but
         * many BIOSes will refuse to boot from a bootsector if the magic is
         * incorrect, so we emit a warning.
         */
        if (!silent && b->end_of_sector_marker != const_cpu_to_le16(0xaa55))
                ntfs_warning(sb, "Invalid end of sector marker.");
        return true;
not_ntfs:
        return false;
}

/**
 * read_ntfs_boot_sector - read the NTFS boot sector of a device
 * @sb:         super block of device to read the boot sector from
 * @silent:     if true, suppress all output
 *
 * Reads the boot sector from the device and validates it. If that fails, tries
 * to read the backup boot sector, first from the end of the device a-la NT4 and
 * later and then from the middle of the device a-la NT3.51 and before.
 *
 * If a valid boot sector is found but it is not the primary boot sector, we
 * repair the primary boot sector silently (unless the device is read-only or
 * the primary boot sector is not accessible).
 *
 * NOTE: To call this function, @sb must have the fields s_dev, the ntfs super
 * block (u.ntfs_sb), nr_blocks and the device flags (s_flags) initialized
 * to their respective values.
 *
 * Return the unlocked buffer head containing the boot sector or NULL on error.
 */
static struct buffer_head *read_ntfs_boot_sector(struct super_block *sb,
                const int silent)
{
        const char *read_err_str = "Unable to read %s boot sector.";
        struct buffer_head *bh_primary, *bh_backup;
        sector_t nr_blocks = NTFS_SB(sb)->nr_blocks;

        /* Try to read primary boot sector. */
        if ((bh_primary = sb_bread(sb, 0))) {
                if (is_boot_sector_ntfs(sb, (NTFS_BOOT_SECTOR*)
                                bh_primary->b_data, silent))
                        return bh_primary;
                if (!silent)
                        ntfs_error(sb, "Primary boot sector is invalid.");
        } else if (!silent)
                ntfs_error(sb, read_err_str, "primary");
        if (!(NTFS_SB(sb)->on_errors & ON_ERRORS_RECOVER)) {
                if (bh_primary)
                        brelse(bh_primary);
                if (!silent)
                        ntfs_error(sb, "Mount option errors=recover not used. "
                                        "Aborting without trying to recover.");
                return NULL;
        }
        /* Try to read NT4+ backup boot sector. */
        if ((bh_backup = sb_bread(sb, nr_blocks - 1))) {
                if (is_boot_sector_ntfs(sb, (NTFS_BOOT_SECTOR*)
                                bh_backup->b_data, silent))
                        goto hotfix_primary_boot_sector;
                brelse(bh_backup);
        } else if (!silent)
                ntfs_error(sb, read_err_str, "backup");
        /* Try to read NT3.51- backup boot sector. */
        if ((bh_backup = sb_bread(sb, nr_blocks >> 1))) {
                if (is_boot_sector_ntfs(sb, (NTFS_BOOT_SECTOR*)
                                bh_backup->b_data, silent))
                        goto hotfix_primary_boot_sector;
                if (!silent)
                        ntfs_error(sb, "Could not find a valid backup boot "
                                        "sector.");
                brelse(bh_backup);
        } else if (!silent)
                ntfs_error(sb, read_err_str, "backup");
        /* We failed. Cleanup and return. */
        if (bh_primary)
                brelse(bh_primary);
        return NULL;
hotfix_primary_boot_sector:
        if (bh_primary) {
                /*
                 * If we managed to read sector zero and the volume is not
                 * read-only, copy the found, valid backup boot sector to the
                 * primary boot sector.  Note we only copy the actual boot
                 * sector structure, not the actual whole device sector as that
                 * may be bigger and would potentially damage the $Boot system
                 * file (FIXME: Would be nice to know if the backup boot sector
                 * on a large sector device contains the whole boot loader or
                 * just the first 512 bytes).
                 */
                if (!(sb->s_flags & MS_RDONLY)) {
                        ntfs_warning(sb, "Hot-fix: Recovering invalid primary "
                                        "boot sector from backup copy.");
                        memcpy(bh_primary->b_data, bh_backup->b_data,
                                        NTFS_BLOCK_SIZE);
                        mark_buffer_dirty(bh_primary);
                        sync_dirty_buffer(bh_primary);
                        if (buffer_uptodate(bh_primary)) {
                                brelse(bh_backup);
                                return bh_primary;
                        }
                        ntfs_error(sb, "Hot-fix: Device write error while "
                                        "recovering primary boot sector.");
                } else {
                        ntfs_warning(sb, "Hot-fix: Recovery of primary boot "
                                        "sector failed: Read-only mount.");
                }
                brelse(bh_primary);
        }
        ntfs_warning(sb, "Using backup boot sector.");
        return bh_backup;
}

/**
 * parse_ntfs_boot_sector - parse the boot sector and store the data in @vol
 * @vol:        volume structure to initialise with data from boot sector
 * @b:          boot sector to parse
 *
 * Parse the ntfs boot sector @b and store all imporant information therein in
 * the ntfs super block @vol.  Return 'true' on success and 'false' on error.
 */
static bool parse_ntfs_boot_sector(ntfs_volume *vol, const NTFS_BOOT_SECTOR *b)
{
        unsigned int sectors_per_cluster_bits, nr_hidden_sects;
        int clusters_per_mft_record, clusters_per_index_record;
        s64 ll;

        vol->sector_size = le16_to_cpu(b->bpb.bytes_per_sector);
        vol->sector_size_bits = ffs(vol->sector_size) - 1;
        ntfs_debug("vol->sector_size = %i (0x%x)", vol->sector_size,
                        vol->sector_size);
        ntfs_debug("vol->sector_size_bits = %i (0x%x)", vol->sector_size_bits,
                        vol->sector_size_bits);
        if (vol->sector_size < vol->sb->s_blocksize) {
                ntfs_error(vol->sb, "Sector size (%i) is smaller than the "
                                "device block size (%lu).  This is not "
                                "supported.  Sorry.", vol->sector_size,
                                vol->sb->s_blocksize);
                return false;
        }
        ntfs_debug("sectors_per_cluster = 0x%x", b->bpb.sectors_per_cluster);
        sectors_per_cluster_bits = ffs(b->bpb.sectors_per_cluster) - 1;
        ntfs_debug("sectors_per_cluster_bits = 0x%x",
                        sectors_per_cluster_bits);
        nr_hidden_sects = le32_to_cpu(b->bpb.hidden_sectors);
        ntfs_debug("number of hidden sectors = 0x%x", nr_hidden_sects);
        vol->cluster_size = vol->sector_size << sectors_per_cluster_bits;
        vol->cluster_size_mask = vol->cluster_size - 1;
        vol->cluster_size_bits = ffs(vol->cluster_size) - 1;
        ntfs_debug("vol->cluster_size = %i (0x%x)", vol->cluster_size,
                        vol->cluster_size);
        ntfs_debug("vol->cluster_size_mask = 0x%x", vol->cluster_size_mask);
        ntfs_debug("vol->cluster_size_bits = %i", vol->cluster_size_bits);
        if (vol->cluster_size < vol->sector_size) {
                ntfs_error(vol->sb, "Cluster size (%i) is smaller than the "
                                "sector size (%i).  This is not supported.  "
                                "Sorry.", vol->cluster_size, vol->sector_size);
                return false;
        }
        clusters_per_mft_record = b->clusters_per_mft_record;
        ntfs_debug("clusters_per_mft_record = %i (0x%x)",
                        clusters_per_mft_record, clusters_per_mft_record);
        if (clusters_per_mft_record > 0)
                vol->mft_record_size = vol->cluster_size <<
                                (ffs(clusters_per_mft_record) - 1);
        else
                /*
                 * When mft_record_size < cluster_size, clusters_per_mft_record
                 * = -log2(mft_record_size) bytes. mft_record_size normaly is
                 * 1024 bytes, which is encoded as 0xF6 (-10 in decimal).
                 */
                vol->mft_record_size = 1 << -clusters_per_mft_record;
        vol->mft_record_size_mask = vol->mft_record_size - 1;
        vol->mft_record_size_bits = ffs(vol->mft_record_size) - 1;
        ntfs_debug("vol->mft_record_size = %i (0x%x)", vol->mft_record_size,
                        vol->mft_record_size);
        ntfs_debug("vol->mft_record_size_mask = 0x%x",
                        vol->mft_record_size_mask);
        ntfs_debug("vol->mft_record_size_bits = %i (0x%x)",
                        vol->mft_record_size_bits, vol->mft_record_size_bits);
        /*
         * We cannot support mft record sizes above the PAGE_CACHE_SIZE since
         * we store $MFT/$DATA, the table of mft records in the page cache.
         */
        if (vol->mft_record_size > PAGE_CACHE_SIZE) {
                ntfs_error(vol->sb, "Mft record size (%i) exceeds the "
                                "PAGE_CACHE_SIZE on your system (%lu).  "
                                "This is not supported.  Sorry.",
                                vol->mft_record_size, PAGE_CACHE_SIZE);
                return false;
        }
        /* We cannot support mft record sizes below the sector size. */
        if (vol->mft_record_size < vol->sector_size) {
                ntfs_error(vol->sb, "Mft record size (%i) is smaller than the "
                                "sector size (%i).  This is not supported.  "
                                "Sorry.", vol->mft_record_size,
                                vol->sector_size);
                return false;
        }
        clusters_per_index_record = b->clusters_per_index_record;
        ntfs_debug("clusters_per_index_record = %i (0x%x)",
                        clusters_per_index_record, clusters_per_index_record);
        if (clusters_per_index_record > 0)
                vol->index_record_size = vol->cluster_size <<
                                (ffs(clusters_per_index_record) - 1);
        else
                /*
                 * When index_record_size < cluster_size,
                 * clusters_per_index_record = -log2(index_record_size) bytes.
                 * index_record_size normaly equals 4096 bytes, which is
                 * encoded as 0xF4 (-12 in decimal).
                 */
                vol->index_record_size = 1 << -clusters_per_index_record;
        vol->index_record_size_mask = vol->index_record_size - 1;
        vol->index_record_size_bits = ffs(vol->index_record_size) - 1;
        ntfs_debug("vol->index_record_size = %i (0x%x)",
                        vol->index_record_size, vol->index_record_size);
        ntfs_debug("vol->index_record_size_mask = 0x%x",
                        vol->index_record_size_mask);
        ntfs_debug("vol->index_record_size_bits = %i (0x%x)",
                        vol->index_record_size_bits,
                        vol->index_record_size_bits);
        /* We cannot support index record sizes below the sector size. */
        if (vol->index_record_size < vol->sector_size) {
                ntfs_error(vol->sb, "Index record size (%i) is smaller than "
                                "the sector size (%i).  This is not "
                                "supported.  Sorry.", vol->index_record_size,
                                vol->sector_size);
                return false;
        }
        /*
         * Get the size of the volume in clusters and check for 64-bit-ness.
         * Windows currently only uses 32 bits to save the clusters so we do
         * the same as it is much faster on 32-bit CPUs.
         */
        ll = sle64_to_cpu(b->number_of_sectors) >> sectors_per_cluster_bits;
        if ((u64)ll >= 1ULL << 32) {
                ntfs_error(vol->sb, "Cannot handle 64-bit clusters.  Sorry.");
                return false;
        }
        vol->nr_clusters = ll;
        ntfs_debug("vol->nr_clusters = 0x%llx", (long long)vol->nr_clusters);
        /*
         * On an architecture where unsigned long is 32-bits, we restrict the
         * volume size to 2TiB (2^41). On a 64-bit architecture, the compiler
         * will hopefully optimize the whole check away.
         */
        if (sizeof(unsigned long) < 8) {
                if ((ll << vol->cluster_size_bits) >= (1ULL << 41)) {
                        ntfs_error(vol->sb, "Volume size (%lluTiB) is too "
                                        "large for this architecture.  "
                                        "Maximum supported is 2TiB.  Sorry.",
                                        (unsigned long long)ll >> (40 -
                                        vol->cluster_size_bits));
                        return false;
                }
        }
        ll = sle64_to_cpu(b->mft_lcn);
        if (ll >= vol->nr_clusters) {
                ntfs_error(vol->sb, "MFT LCN (%lli, 0x%llx) is beyond end of "
                                "volume.  Weird.", (unsigned long long)ll,
                                (unsigned long long)ll);
                return false;
        }
        vol->mft_lcn = ll;
        ntfs_debug("vol->mft_lcn = 0x%llx", (long long)vol->mft_lcn);
        ll = sle64_to_cpu(b->mftmirr_lcn);
        if (ll >= vol->nr_clusters) {
                ntfs_error(vol->sb, "MFTMirr LCN (%lli, 0x%llx) is beyond end "
                                "of volume.  Weird.", (unsigned long long)ll,
                                (unsigned long long)ll);
                return false;
        }
        vol->mftmirr_lcn = ll;
        ntfs_debug("vol->mftmirr_lcn = 0x%llx", (long long)vol->mftmirr_lcn);
#ifdef NTFS_RW
        /*
         * Work out the size of the mft mirror in number of mft records. If the
         * cluster size is less than or equal to the size taken by four mft
         * records, the mft mirror stores the first four mft records. If the
         * cluster size is bigger than the size taken by four mft records, the
         * mft mirror contains as many mft records as will fit into one
         * cluster.
         */
        if (vol->cluster_size <= (4 << vol->mft_record_size_bits))
                vol->mftmirr_size = 4;
        else
                vol->mftmirr_size = vol->cluster_size >>
                                vol->mft_record_size_bits;
        ntfs_debug("vol->mftmirr_size = %i", vol->mftmirr_size);
#endif /* NTFS_RW */
        vol->serial_no = le64_to_cpu(b->volume_serial_number);
        ntfs_debug("vol->serial_no = 0x%llx",
                        (unsigned long long)vol->serial_no);
        return true;
}

/**
 * ntfs_setup_allocators - initialize the cluster and mft allocators
 * @vol:        volume structure for which to setup the allocators
 *
 * Setup the cluster (lcn) and mft allocators to the starting values.
 */
static void ntfs_setup_allocators(ntfs_volume *vol)
{
#ifdef NTFS_RW
        LCN mft_zone_size, mft_lcn;
#endif /* NTFS_RW */

        ntfs_debug("vol->mft_zone_multiplier = 0x%x",
                        vol->mft_zone_multiplier);
#ifdef NTFS_RW
        /* Determine the size of the MFT zone. */
        mft_zone_size = vol->nr_clusters;
        switch (vol->mft_zone_multiplier) {  /* % of volume size in clusters */
        case 4:
                mft_zone_size >>= 1;                    /* 50%   */
                break;
        case 3:
                mft_zone_size = (mft_zone_size +
                                (mft_zone_size >> 1)) >> 2;     /* 37.5% */
                break;
        case 2:
                mft_zone_size >>= 2;                    /* 25%   */
                break;
        /* case 1: */
        default:
                mft_zone_size >>= 3;                    /* 12.5% */
                break;
        }
        /* Setup the mft zone. */
        vol->mft_zone_start = vol->mft_zone_pos = vol->mft_lcn;
        ntfs_debug("vol->mft_zone_pos = 0x%llx",
                        (unsigned long long)vol->mft_zone_pos);
        /*
         * Calculate the mft_lcn for an unmodified NTFS volume (see mkntfs
         * source) and if the actual mft_lcn is in the expected place or even
         * further to the front of the volume, extend the mft_zone to cover the
         * beginning of the volume as well.  This is in order to protect the
         * area reserved for the mft bitmap as well within the mft_zone itself.
         * On non-standard volumes we do not protect it as the overhead would
         * be higher than the speed increase we would get by doing it.
         */
        mft_lcn = (8192 + 2 * vol->cluster_size - 1) / vol->cluster_size;
        if (mft_lcn * vol->cluster_size < 16 * 1024)
                mft_lcn = (16 * 1024 + vol->cluster_size - 1) /
                                vol->cluster_size;
        if (vol->mft_zone_start <= mft_lcn)
                vol->mft_zone_start = 0;
        ntfs_debug("vol->mft_zone_start = 0x%llx",
                        (unsigned long long)vol->mft_zone_start);
        /*
         * Need to cap the mft zone on non-standard volumes so that it does
         * not point outside the boundaries of the volume.  We do this by
         * halving the zone size until we are inside the volume.
         */
        vol->mft_zone_end = vol->mft_lcn + mft_zone_size;
        while (vol->mft_zone_end >= vol->nr_clusters) {
                mft_zone_size >>= 1;
                vol->mft_zone_end = vol->mft_lcn + mft_zone_size;
        }
        ntfs_debug("vol->mft_zone_end = 0x%llx",
                        (unsigned long long)vol->mft_zone_end);
        /*
         * Set the current position within each data zone to the start of the
         * respective zone.
         */
        vol->data1_zone_pos = vol->mft_zone_end;
        ntfs_debug("vol->data1_zone_pos = 0x%llx",
                        (unsigned long long)vol->data1_zone_pos);
        vol->data2_zone_pos = 0;
        ntfs_debug("vol->data2_zone_pos = 0x%llx",
                        (unsigned long long)vol->data2_zone_pos);

        /* Set the mft data allocation position to mft record 24. */
        vol->mft_data_pos = 24;
        ntfs_debug("vol->mft_data_pos = 0x%llx",
                        (unsigned long long)vol->mft_data_pos);
#endif /* NTFS_RW */
}

#ifdef NTFS_RW

/**
 * load_and_init_mft_mirror - load and setup the mft mirror inode for a volume

 * @vol:        ntfs super block describing device whose mft mirror to load
 *
 * Return 'true' on success or 'false' on error.
 */
static bool load_and_init_mft_mirror(ntfs_volume *vol)
{
        struct inode *tmp_ino;
        ntfs_inode *tmp_ni;

        ntfs_debug("Entering.");
        /* Get mft mirror inode. */
        tmp_ino = ntfs_iget(vol->sb, FILE_MFTMirr);
        if (IS_ERR(tmp_ino) || is_bad_inode(tmp_ino)) {
                if (!IS_ERR(tmp_ino))
                        iput(tmp_ino);
                /* Caller will display error message. */
                return false;
        }
        /*
         * Re-initialize some specifics about $MFTMirr's inode as
         * ntfs_read_inode() will have set up the default ones.
         */
        /* Set uid and gid to root. */
        tmp_ino->i_uid = tmp_ino->i_gid = 0;
        /* Regular file.  No access for anyone. */
        tmp_ino->i_mode = S_IFREG;
        /* No VFS initiated operations allowed for $MFTMirr. */
        tmp_ino->i_op = &ntfs_empty_inode_ops;
        tmp_ino->i_fop = &ntfs_empty_file_ops;
        /* Put in our special address space operations. */
        tmp_ino->i_mapping->a_ops = &ntfs_mst_aops;
        tmp_ni = NTFS_I(tmp_ino);
        /* The $MFTMirr, like the $MFT is multi sector transfer protected. */
        NInoSetMstProtected(tmp_ni);
        NInoSetSparseDisabled(tmp_ni);
        /*
         * Set up our little cheat allowing us to reuse the async read io
         * completion handler for directories.
         */
        tmp_ni->itype.index.block_size = vol->mft_record_size;
        tmp_ni->itype.index.block_size_bits = vol->mft_record_size_bits;
        vol->mftmirr_ino = tmp_ino;
        ntfs_debug("Done.");
        return true;
}

/**
 * check_mft_mirror - compare contents of the mft mirror with the mft
 * @vol:        ntfs super block describing device whose mft mirror to check
 *
 * Return 'true' on success or 'false' on error.
 *
 * Note, this function also results in the mft mirror runlist being completely
 * mapped into memory.  The mft mirror write code requires this and will BUG()
 * should it find an unmapped runlist element.
 */
static bool check_mft_mirror(ntfs_volume *vol)
{
        struct super_block *sb = vol->sb;
        ntfs_inode *mirr_ni;
        struct page *mft_page, *mirr_page;
        u8 *kmft, *kmirr;
        runlist_element *rl, rl2[2];
        pgoff_t index;
        int mrecs_per_page, i;

        ntfs_debug("Entering.");
        /* Compare contents of $MFT and $MFTMirr. */
        mrecs_per_page = PAGE_CACHE_SIZE / vol->mft_record_size;
        BUG_ON(!mrecs_per_page);
        BUG_ON(!vol->mftmirr_size);
        mft_page = mirr_page = NULL;
        kmft = kmirr = NULL;
        index = i = 0;
        do {
                u32 bytes;

                /* Switch pages if necessary. */
                if (!(i % mrecs_per_page)) {
                        if (index) {
                                ntfs_unmap_page(mft_page);
                                ntfs_unmap_page(mirr_page);
                        }
                        /* Get the $MFT page. */
                        mft_page = ntfs_map_page(vol->mft_ino->i_mapping,
                                        index);
                        if (IS_ERR(mft_page)) {
                                ntfs_error(sb, "Failed to read $MFT.");
                                return false;
                        }
                        kmft = page_address(mft_page);
                        /* Get the $MFTMirr page. */
                        mirr_page = ntfs_map_page(vol->mftmirr_ino->i_mapping,
                                        index);
                        if (IS_ERR(mirr_page)) {
                                ntfs_error(sb, "Failed to read $MFTMirr.");
                                goto mft_unmap_out;
                        }
                        kmirr = page_address(mirr_page);
                        ++index;
                }
                /* Do not check the record if it is not in use. */
                if (((MFT_RECORD*)kmft)->flags & MFT_RECORD_IN_USE) {
                        /* Make sure the record is ok. */
                        if (ntfs_is_baad_recordp((le32*)kmft)) {
                                ntfs_error(sb, "Incomplete multi sector "
                                                "transfer detected in mft "
                                                "record %i.", i);
mm_unmap_out:
                                ntfs_unmap_page(mirr_page);
mft_unmap_out:
                                ntfs_unmap_page(mft_page);
                                return false;
                        }
                }
                /* Do not check the mirror record if it is not in use. */
                if (((MFT_RECORD*)kmirr)->flags & MFT_RECORD_IN_USE) {
                        if (ntfs_is_baad_recordp((le32*)kmirr)) {
                                ntfs_error(sb, "Incomplete multi sector "
                                                "transfer detected in mft "
                                                "mirror record %i.", i);
                                goto mm_unmap_out;
                        }
                }
                /* Get the amount of data in the current record. */
                bytes = le32_to_cpu(((MFT_RECORD*)kmft)->bytes_in_use);
                if (bytes < sizeof(MFT_RECORD_OLD) ||
                                bytes > vol->mft_record_size ||
                                ntfs_is_baad_recordp((le32*)kmft)) {
                        bytes = le32_to_cpu(((MFT_RECORD*)kmirr)->bytes_in_use);
                        if (bytes < sizeof(MFT_RECORD_OLD) ||
                                        bytes > vol->mft_record_size ||
                                        ntfs_is_baad_recordp((le32*)kmirr))
                                bytes = vol->mft_record_size;
                }
                /* Compare the two records. */
                if (memcmp(kmft, kmirr, bytes)) {
                        ntfs_error(sb, "$MFT and $MFTMirr (record %i) do not "
                                        "match.  Run ntfsfix or chkdsk.", i);
                        goto mm_unmap_out;
                }
                kmft += vol->mft_record_size;
                kmirr += vol->mft_record_size;
        } while (++i < vol->mftmirr_size);
        /* Release the last pages. */
        ntfs_unmap_page(mft_page);
        ntfs_unmap_page(mirr_page);

        /* Construct the mft mirror runlist by hand. */
        rl2[0].vcn = 0;
        rl2[0].lcn = vol->mftmirr_lcn;
        rl2[0].length = (vol->mftmirr_size * vol->mft_record_size +
                        vol->cluster_size - 1) / vol->cluster_size;
        rl2[1].vcn = rl2[0].length;
        rl2[1].lcn = LCN_ENOENT;
        rl2[1].length = 0;
        /*
         * Because we have just read all of the mft mirror, we know we have
         * mapped the full runlist for it.
         */
        mirr_ni = NTFS_I(vol->mftmirr_ino);
        down_read(&mirr_ni->runlist.lock);
        rl = mirr_ni->runlist.rl;
        /* Compare the two runlists.  They must be identical. */
        i = 0;
        do {
                if (rl2[i].vcn != rl[i].vcn || rl2[i].lcn != rl[i].lcn ||
                                rl2[i].length != rl[i].length) {
                        ntfs_error(sb, "$MFTMirr location mismatch.  "
                                        "Run chkdsk.");
                        up_read(&mirr_ni->runlist.lock);
                        return false;
                }
        } while (rl2[i++].length);
        up_read(&mirr_ni->runlist.lock);
        ntfs_debug("Done.");
        return true;
}

/**
 * load_and_check_logfile - load and check the logfile inode for a volume
 * @vol:        ntfs super block describing device whose logfile to load
 *
 * Return 'true' on success or 'false' on error.
 */
static bool load_and_check_logfile(ntfs_volume *vol,
                RESTART_PAGE_HEADER **rp)
{
        struct inode *tmp_ino;

        ntfs_debug("Entering.");
        tmp_ino = ntfs_iget(vol->sb, FILE_LogFile);
        if (IS_ERR(tmp_ino) || is_bad_inode(tmp_ino)) {
                if (!IS_ERR(tmp_ino))
                        iput(tmp_ino);
                /* Caller will display error message. */
                return false;
        }
        if (!ntfs_check_logfile(tmp_ino, rp)) {
                iput(tmp_ino);
                /* ntfs_check_logfile() will have displayed error output. */
                return false;
        }
        NInoSetSparseDisabled(NTFS_I(tmp_ino));
        vol->logfile_ino = tmp_ino;
        ntfs_debug("Done.");
        return true;
}

#define NTFS_HIBERFIL_HEADER_SIZE       4096

/**
 * check_windows_hibernation_status - check if Windows is suspended on a volume
 * @vol:        ntfs super block of device to check
 *
 * Check if Windows is hibernated on the ntfs volume @vol.  This is done by
 * looking for the file hiberfil.sys in the root directory of the volume.  If
 * the file is not present Windows is definitely not suspended.
 *
 * If hiberfil.sys exists and is less than 4kiB in size it means Windows is
 * definitely suspended (this volume is not the system volume).  Caveat:  on a
 * system with many volumes it is possible that the < 4kiB check is bogus but
 * for now this should do fine.
 *
 * If hiberfil.sys exists and is larger than 4kiB in size, we need to read the
 * hiberfil header (which is the first 4kiB).  If this begins with "hibr",
 * Windows is definitely suspended.  If it is completely full of zeroes,
 * Windows is definitely not hibernated.  Any other case is treated as if
 * Windows is suspended.  This caters for the above mentioned caveat of a
 * system with many volumes where no "hibr" magic would be present and there is
 * no zero header.
 *
 * Return 0 if Windows is not hibernated on the volume, >0 if Windows is
 * hibernated on the volume, and -errno on error.
 */
static int check_windows_hibernation_status(ntfs_volume *vol)
{
        MFT_REF mref;
        struct inode *vi;
        ntfs_inode *ni;
        struct page *page;
        u32 *kaddr, *kend;
        ntfs_name *name = NULL;
        int ret = 1;
        static const ntfschar hiberfil[13] = { const_cpu_to_le16('h'),
                        const_cpu_to_le16('i'), const_cpu_to_le16('b'),
                        const_cpu_to_le16('e'), const_cpu_to_le16('r'),
                        const_cpu_to_le16('f'), const_cpu_to_le16('i'),
                        const_cpu_to_le16('l'), const_cpu_to_le16('.'),
                        const_cpu_to_le16('s'), const_cpu_to_le16('y'),
                        const_cpu_to_le16('s'), 0 };

        ntfs_debug("Entering.");
        /*
         * Find the inode number for the hibernation file by looking up the
         * filename hiberfil.sys in the root directory.
         */
        mutex_lock(&vol->root_ino->i_mutex);
        mref = ntfs_lookup_inode_by_name(NTFS_I(vol->root_ino), hiberfil, 12,
                        &name);
        mutex_unlock(&vol->root_ino->i_mutex);
        if (IS_ERR_MREF(mref)) {
                ret = MREF_ERR(mref);
                /* If the file does not exist, Windows is not hibernated. */
                if (ret == -ENOENT) {
                        ntfs_debug("hiberfil.sys not present.  Windows is not "
                                        "hibernated on the volume.");
                        return 0;
                }
                /* A real error occured. */
                ntfs_error(vol->sb, "Failed to find inode number for "
                                "hiberfil.sys.");
                return ret;
        }
        /* We do not care for the type of match that was found. */
        kfree(name);
        /* Get the inode. */
        vi = ntfs_iget(vol->sb, MREF(mref));
        if (IS_ERR(vi) || is_bad_inode(vi)) {
                if (!IS_ERR(vi))
                        iput(vi);
                ntfs_error(vol->sb, "Failed to load hiberfil.sys.");
                return IS_ERR(vi) ? PTR_ERR(vi) : -EIO;
        }
        if (unlikely(i_size_read(vi) < NTFS_HIBERFIL_HEADER_SIZE)) {
                ntfs_debug("hiberfil.sys is smaller than 4kiB (0x%llx).  "
                                "Windows is hibernated on the volume.  This "
                                "is not the system volume.", i_size_read(vi));
                goto iput_out;
        }
        ni = NTFS_I(vi);
        page = ntfs_map_page(vi->i_mapping, 0);
        if (IS_ERR(page)) {
                ntfs_error(vol->sb, "Failed to read from hiberfil.sys.");
                ret = PTR_ERR(page);
                goto iput_out;
        }
        kaddr = (u32*)page_address(page);
        if (*(le32*)kaddr == const_cpu_to_le32(0x72626968)/*'hibr'*/) {
                ntfs_debug("Magic \"hibr\" found in hiberfil.sys.  Windows is "
                                "hibernated on the volume.  This is the "
                                "system volume.");
                goto unm_iput_out;
        }
        kend = kaddr + NTFS_HIBERFIL_HEADER_SIZE/sizeof(*kaddr);
        do {
                if (unlikely(*kaddr)) {
                        ntfs_debug("hiberfil.sys is larger than 4kiB "
                                        "(0x%llx), does not contain the "
                                        "\"hibr\" magic, and does not have a "
                                        "zero header.  Windows is hibernated "
                                        "on the volume.  This is not the "
                                        "system volume.", i_size_read(vi));
                        goto unm_iput_out;
                }
        } while (++kaddr < kend);
        ntfs_debug("hiberfil.sys contains a zero header.  Windows is not "
                        "hibernated on the volume.  This is the system "
                        "volume.");
        ret = 0;
unm_iput_out:
        ntfs_unmap_page(page);
iput_out:
        iput(vi);
        return ret;
}

/**
 * load_and_init_quota - load and setup the quota file for a volume if present
 * @vol:        ntfs super block describing device whose quota file to load
 *
 * Return 'true' on success or 'false' on error.  If $Quota is not present, we
 * leave vol->quota_ino as NULL and return success.
 */
static bool load_and_init_quota(ntfs_volume *vol)
{
        MFT_REF mref;
        struct inode *tmp_ino;
        ntfs_name *name = NULL;
        static const ntfschar Quota[7] = { const_cpu_to_le16('$'),
                        const_cpu_to_le16('Q'), const_cpu_to_le16('u'),
                        const_cpu_to_le16('o'), const_cpu_to_le16('t'),
                        const_cpu_to_le16('a'), 0 };
        static ntfschar Q[3] = { const_cpu_to_le16('$'),
                        const_cpu_to_le16('Q'), 0 };

        ntfs_debug("Entering.");
        /*
         * Find the inode number for the quota file by looking up the filename
         * $Quota in the extended system files directory $Extend.
         */
        mutex_lock(&vol->extend_ino->i_mutex);
        mref = ntfs_lookup_inode_by_name(NTFS_I(vol->extend_ino), Quota, 6,
                        &name);
        mutex_unlock(&vol->extend_ino->i_mutex);
        if (IS_ERR_MREF(mref)) {
                /*
                 * If the file does not exist, quotas are disabled and have
                 * never been enabled on this volume, just return success.
                 */
                if (MREF_ERR(mref) == -ENOENT) {
                        ntfs_debug("$Quota not present.  Volume does not have "
                                        "quotas enabled.");
                        /*
                         * No need to try to set quotas out of date if they are
                         * not enabled.
                         */
                        NVolSetQuotaOutOfDate(vol);
                        return true;
                }
                /* A real error occured. */
                ntfs_error(vol->sb, "Failed to find inode number for $Quota.");
                return false;
        }
        /* We do not care for the type of match that was found. */
        kfree(name);
        /* Get the inode. */
        tmp_ino = ntfs_iget(vol->sb, MREF(mref));
        if (IS_ERR(tmp_ino) || is_bad_inode(tmp_ino)) {
                if (!IS_ERR(tmp_ino))
                        iput(tmp_ino);
                ntfs_error(vol->sb, "Failed to load $Quota.");
                return false;
        }
        vol->quota_ino = tmp_ino;
        /* Get the $Q index allocation attribute. */
        tmp_ino = ntfs_index_iget(vol->quota_ino, Q, 2);
        if (IS_ERR(tmp_ino)) {
                ntfs_error(vol->sb, "Failed to load $Quota/$Q index.");
                return false;
        }
        vol->quota_q_ino = tmp_ino;
        ntfs_debug("Done.");
        return true;
}

/**
 * load_and_init_usnjrnl - load and setup the transaction log if present
 * @vol:        ntfs super block describing device whose usnjrnl file to load
 *
 * Return 'true' on success or 'false' on error.
 *
 * If $UsnJrnl is not present or in the process of being disabled, we set
 * NVolUsnJrnlStamped() and return success.
 *
 * If the $UsnJrnl $DATA/$J attribute has a size equal to the lowest valid usn,
 * i.e. transaction logging has only just been enabled or the journal has been
 * stamped and nothing has been logged since, we also set NVolUsnJrnlStamped()
 * and return success.
 */
static bool load_and_init_usnjrnl(ntfs_volume *vol)
{
        MFT_REF mref;
        struct inode *tmp_ino;
        ntfs_inode *tmp_ni;
        struct page *page;
        ntfs_name *name = NULL;
        USN_HEADER *uh;
        static const ntfschar UsnJrnl[9] = { const_cpu_to_le16('$'),
                        const_cpu_to_le16('U'), const_cpu_to_le16('s'),
                        const_cpu_to_le16('n'), const_cpu_to_le16('J'),
                        const_cpu_to_le16('r'), const_cpu_to_le16('n'),
                        const_cpu_to_le16('l'), 0 };
        static ntfschar Max[5] = { const_cpu_to_le16('$'),
                        const_cpu_to_le16('M'), const_cpu_to_le16('a'),
                        const_cpu_to_le16('x'), 0 };
        static ntfschar J[3] = { const_cpu_to_le16('$'),
                        const_cpu_to_le16('J'), 0 };

        ntfs_debug("Entering.");
        /*
         * Find the inode number for the transaction log file by looking up the
         * filename $UsnJrnl in the extended system files directory $Extend.
         */
        mutex_lock(&vol->extend_ino->i_mutex);
        mref = ntfs_lookup_inode_by_name(NTFS_I(vol->extend_ino), UsnJrnl, 8,
                        &name);
        mutex_unlock(&vol->extend_ino->i_mutex);
        if (IS_ERR_MREF(mref)) {
                /*
                 * If the file does not exist, transaction logging is disabled,
                 * just return success.
                 */
                if (MREF_ERR(mref) == -ENOENT) {
                        ntfs_debug("$UsnJrnl not present.  Volume does not "
                                        "have transaction logging enabled.");
not_enabled:
                        /*
                         * No need to try to stamp the transaction log if
                         * transaction logging is not enabled.
                         */
                        NVolSetUsnJrnlStamped(vol);
                        return true;
                }
                /* A real error occured. */
                ntfs_error(vol->sb, "Failed to find inode number for "
                                "$UsnJrnl.");
                return false;
        }
        /* We do not care for the type of match that was found. */
        kfree(name);
        /* Get the inode. */
        tmp_ino = ntfs_iget(vol->sb, MREF(mref));
        if (unlikely(IS_ERR(tmp_ino) || is_bad_inode(tmp_ino))) {
                if (!IS_ERR(tmp_ino))
                        iput(tmp_ino);
                ntfs_error(vol->sb, "Failed to load $UsnJrnl.");
                return false;
        }
        vol->usnjrnl_ino = tmp_ino;
        /*
         * If the transaction log is in the process of being deleted, we can
         * ignore it.
         */
        if (unlikely(vol->vol_flags & VOLUME_DELETE_USN_UNDERWAY)) {
                ntfs_debug("$UsnJrnl in the process of being disabled.  "
                                "Volume does not have transaction logging "
                                "enabled.");
                goto not_enabled;
        }
        /* Get the $DATA/$Max attribute. */
        tmp_ino = ntfs_attr_iget(vol->usnjrnl_ino, AT_DATA, Max, 4);
        if (IS_ERR(tmp_ino)) {
                ntfs_error(vol->sb, "Failed to load $UsnJrnl/$DATA/$Max "
                                "attribute.");
                return false;
        }
        vol->usnjrnl_max_ino = tmp_ino;
        if (unlikely(i_size_read(tmp_ino) < sizeof(USN_HEADER))) {
                ntfs_error(vol->sb, "Found corrupt $UsnJrnl/$DATA/$Max "
                                "attribute (size is 0x%llx but should be at "
                                "least 0x%zx bytes).", i_size_read(tmp_ino),
                                sizeof(USN_HEADER));
                return false;
        }
        /* Get the $DATA/$J attribute. */
        tmp_ino = ntfs_attr_iget(vol->usnjrnl_ino, AT_DATA, J, 2);
        if (IS_ERR(tmp_ino)) {
                ntfs_error(vol->sb, "Failed to load $UsnJrnl/$DATA/$J "
                                "attribute.");
                return false;
        }
        vol->usnjrnl_j_ino = tmp_ino;
        /* Verify $J is non-resident and sparse. */
        tmp_ni = NTFS_I(vol->usnjrnl_j_ino);
        if (unlikely(!NInoNonResident(tmp_ni) || !NInoSparse(tmp_ni))) {
                ntfs_error(vol->sb, "$UsnJrnl/$DATA/$J attribute is resident "
                                "and/or not sparse.");
                return false;
        }
        /* Read the USN_HEADER from $DATA/$Max. */
        page = ntfs_map_page(vol->usnjrnl_max_ino->i_mapping, 0);
        if (IS_ERR(page)) {
                ntfs_error(vol->sb, "Failed to read from $UsnJrnl/$DATA/$Max "
                                "attribute.");
                return false;
        }
        uh = (USN_HEADER*)page_address(page);
        /* Sanity check the $Max. */
        if (unlikely(sle64_to_cpu(uh->allocation_delta) >
                        sle64_to_cpu(uh->maximum_size))) {
                ntfs_error(vol->sb, "Allocation delta (0x%llx) exceeds "
                                "maximum size (0x%llx).  $UsnJrnl is corrupt.",
                                (long long)sle64_to_cpu(uh->allocation_delta),
                                (long long)sle64_to_cpu(uh->maximum_size));
                ntfs_unmap_page(page);
                return false;
        }
        /*
         * If the transaction log has been stamped and nothing has been written
         * to it since, we do not need to stamp it.
         */
        if (unlikely(sle64_to_cpu(uh->lowest_valid_usn) >=
                        i_size_read(vol->usnjrnl_j_ino))) {
                if (likely(sle64_to_cpu(uh->lowest_valid_usn) ==
                                i_size_read(vol->usnjrnl_j_ino))) {
                        ntfs_unmap_page(page);
                        ntfs_debug("$UsnJrnl is enabled but nothing has been "
                                        "logged since it was last stamped.  "
                                        "Treating this as if the volume does "
                                        "not have transaction logging "
                                        "enabled.");
                        goto not_enabled;
                }
                ntfs_error(vol->sb, "$UsnJrnl has lowest valid usn (0x%llx) "
                                "which is out of bounds (0x%llx).  $UsnJrnl "
                                "is corrupt.",
                                (long long)sle64_to_cpu(uh->lowest_valid_usn),
                                i_size_read(vol->usnjrnl_j_ino));
                ntfs_unmap_page(page);
                return false;
        }
        ntfs_unmap_page(page);
        ntfs_debug("Done.");
        return true;
}

/**
 * load_and_init_attrdef - load the attribute definitions table for a volume
 * @vol:        ntfs super block describing device whose attrdef to load
 *
 * Return 'true' on success or 'false' on error.
 */
static bool load_and_init_attrdef(ntfs_volume *vol)
{
        loff_t i_size;
        struct super_block *sb = vol->sb;
        struct inode *ino;
        struct page *page;
        pgoff_t index, max_index;
        unsigned int size;

        ntfs_debug("Entering.");
        /* Read attrdef table and setup vol->attrdef and vol->attrdef_size. */
        ino = ntfs_iget(sb, FILE_AttrDef);
        if (IS_ERR(ino) || is_bad_inode(ino)) {
                if (!IS_ERR(ino))
                        iput(ino);
                goto failed;
        }
        NInoSetSparseDisabled(NTFS_I(ino));
        /* The size of FILE_AttrDef must be above 0 and fit inside 31 bits. */
        i_size = i_size_read(ino);
        if (i_size <= 0 || i_size > 0x7fffffff)
                goto iput_failed;
        vol->attrdef = (ATTR_DEF*)ntfs_malloc_nofs(i_size);
        if (!vol->attrdef)
                goto iput_failed;
        index = 0;
        max_index = i_size >> PAGE_CACHE_SHIFT;
        size = PAGE_CACHE_SIZE;
        while (index < max_index) {
                /* Read the attrdef table and copy it into the linear buffer. */
read_partial_attrdef_page:
                page = ntfs_map_page(ino->i_mapping, index);
                if (IS_ERR(page))
                        goto free_iput_failed;
                memcpy((u8*)vol->attrdef + (index++ << PAGE_CACHE_SHIFT),
                                page_address(page), size);
                ntfs_unmap_page(page);
        };
        if (size == PAGE_CACHE_SIZE) {
                size = i_size & ~PAGE_CACHE_MASK;
                if (size)
                        goto read_partial_attrdef_page;
        }
        vol->attrdef_size = i_size;
        ntfs_debug("Read %llu bytes from $AttrDef.", i_size);
        iput(ino);
        return true;
free_iput_failed:
        ntfs_free(vol->attrdef);
        vol->attrdef = NULL;
iput_failed:
        iput(ino);
failed:
        ntfs_error(sb, "Failed to initialize attribute definition table.");
        return false;
}

#endif /* NTFS_RW */

/**
 * load_and_init_upcase - load the upcase table for an ntfs volume
 * @vol:        ntfs super block describing device whose upcase to load
 *
 * Return 'true' on success or 'false' on error.
 */
static bool load_and_init_upcase(ntfs_volume *vol)
{
        loff_t i_size;
        struct super_block *sb = vol->sb;
        struct inode *ino;
        struct page *page;
        pgoff_t index, max_index;
        unsigned int size;
        int i, max;

        ntfs_debug("Entering.");
        /* Read upcase table and setup vol->upcase and vol->upcase_len. */
        ino = ntfs_iget(sb, FILE_UpCase);
        if (IS_ERR(ino) || is_bad_inode(ino)) {
                if (!IS_ERR(ino))
                        iput(ino);
                goto upcase_failed;
        }
        /*
         * The upcase size must not be above 64k Unicode characters, must not
         * be zero and must be a multiple of sizeof(ntfschar).
         */
        i_size = i_size_read(ino);
        if (!i_size || i_size & (sizeof(ntfschar) - 1) ||
                        i_size > 64ULL * 1024 * sizeof(ntfschar))
                goto iput_upcase_failed;
        vol->upcase = (ntfschar*)ntfs_malloc_nofs(i_size);
        if (!vol->upcase)
                goto iput_upcase_failed;
        index = 0;
        max_index = i_size >> PAGE_CACHE_SHIFT;
        size = PAGE_CACHE_SIZE;
        while (index < max_index) {
                /* Read the upcase table and copy it into the linear buffer. */
read_partial_upcase_page:
                page = ntfs_map_page(ino->i_mapping, index);
                if (IS_ERR(page))
                        goto iput_upcase_failed;
                memcpy((char*)vol->upcase + (index++ << PAGE_CACHE_SHIFT),
                                page_address(page), size);
                ntfs_unmap_page(page);
        };
        if (size == PAGE_CACHE_SIZE) {
                size = i_size & ~PAGE_CACHE_MASK;
                if (size)
                        goto read_partial_upcase_page;
        }
        vol->upcase_len = i_size >> UCHAR_T_SIZE_BITS;
        ntfs_debug("Read %llu bytes from $UpCase (expected %zu bytes).",
                        i_size, 64 * 1024 * sizeof(ntfschar));
        iput(ino);
        mutex_lock(&ntfs_lock);
        if (!default_upcase) {
                ntfs_debug("Using volume specified $UpCase since default is "
                                "not present.");
                mutex_unlock(&ntfs_lock);
                return true;
        }
        max = default_upcase_len;
        if (max > vol->upcase_len)
                max = vol->upcase_len;
        for (i = 0; i < max; i++)
                if (vol->upcase[i] != default_upcase[i])
                        break;
        if (i == max) {
                ntfs_free(vol->upcase);
                vol->upcase = default_upcase;
                vol->upcase_len = max;
                ntfs_nr_upcase_users++;
                mutex_unlock(&ntfs_lock);
                ntfs_debug("Volume specified $UpCase matches default. Using "
                                "default.");
                return true;
        }
        mutex_unlock(&ntfs_lock);
        ntfs_debug("Using volume specified $UpCase since it does not match "
                        "the default.");
        return true;
iput_upcase_failed:
        iput(ino);
        ntfs_free(vol->upcase);
        vol->upcase = NULL;
upcase_failed:
        mutex_lock(&ntfs_lock);
        if (default_upcase) {
                vol->upcase = default_upcase;
                vol->upcase_len = default_upcase_len;
                ntfs_nr_upcase_users++;
                mutex_unlock(&ntfs_lock);
                ntfs_error(sb, "Failed to load $UpCase from the volume. Using "
                                "default.");
                return true;
        }
        mutex_unlock(&ntfs_lock);
        ntfs_error(sb, "Failed to initialize upcase table.");
        return false;
}

/*
 * The lcn and mft bitmap inodes are NTFS-internal inodes with
 * their own special locking rules:
 */
static struct lock_class_key
        lcnbmp_runlist_lock_key, lcnbmp_mrec_lock_key,
        mftbmp_runlist_lock_key, mftbmp_mrec_lock_key;

/**
 * load_system_files - open the system files using normal functions
 * @vol:        ntfs super block describing device whose system files to load
 *
 * Open the system files with normal access functions and complete setting up
 * the ntfs super block @vol.
 *
 * Return 'true' on success or 'false' on error.
 */
static bool load_system_files(ntfs_volume *vol)
{
        struct super_block *sb = vol->sb;
        MFT_RECORD *m;
        VOLUME_INFORMATION *vi;
        ntfs_attr_search_ctx *ctx;
#ifdef NTFS_RW
        RESTART_PAGE_HEADER *rp;
        int err;
#endif /* NTFS_RW */

        ntfs_debug("Entering.");
#ifdef NTFS_RW
        /* Get mft mirror inode compare the contents of $MFT and $MFTMirr. */
        if (!load_and_init_mft_mirror(vol) || !check_mft_mirror(vol)) {
                static const char *es1 = "Failed to load $MFTMirr";
                static const char *es2 = "$MFTMirr does not match $MFT";
                static const char *es3 = ".  Run ntfsfix and/or chkdsk.";

                /* If a read-write mount, convert it to a read-only mount. */
                if (!(sb->s_flags & MS_RDONLY)) {
                        if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
                                        ON_ERRORS_CONTINUE))) {
                                ntfs_error(sb, "%s and neither on_errors="
                                                "continue nor on_errors="
                                                "remount-ro was specified%s",
                                                !vol->mftmirr_ino ? es1 : es2,
                                                es3);
                                goto iput_mirr_err_out;
                        }
                        sb->s_flags |= MS_RDONLY;
                        ntfs_error(sb, "%s.  Mounting read-only%s",
                                        !vol->mftmirr_ino ? es1 : es2, es3);
                } else
                        ntfs_warning(sb, "%s.  Will not be able to remount "
                                        "read-write%s",
                                        !vol->mftmirr_ino ? es1 : es2, es3);
                /* This will prevent a read-write remount. */
                NVolSetErrors(vol);
        }
#endif /* NTFS_RW */
        /* Get mft bitmap attribute inode. */
        vol->mftbmp_ino = ntfs_attr_iget(vol->mft_ino, AT_BITMAP, NULL, 0);
        if (IS_ERR(vol->mftbmp_ino)) {
                ntfs_error(sb, "Failed to load $MFT/$BITMAP attribute.");
                goto iput_mirr_err_out;
        }
        lockdep_set_class(&NTFS_I(vol->mftbmp_ino)->runlist.lock,
                           &mftbmp_runlist_lock_key);
        lockdep_set_class(&NTFS_I(vol->mftbmp_ino)->mrec_lock,
                           &mftbmp_mrec_lock_key);
        /* Read upcase table and setup @vol->upcase and @vol->upcase_len. */
        if (!load_and_init_upcase(vol))
                goto iput_mftbmp_err_out;
#ifdef NTFS_RW
        /*
         * Read attribute definitions table and setup @vol->attrdef and
         * @vol->attrdef_size.
         */
        if (!load_and_init_attrdef(vol))
                goto iput_upcase_err_out;
#endif /* NTFS_RW */
        /*
         * Get the cluster allocation bitmap inode and verify the size, no
         * need for any locking at this stage as we are already running
         * exclusively as we are mount in progress task.
         */
        vol->lcnbmp_ino = ntfs_iget(sb, FILE_Bitmap);
        if (IS_ERR(vol->lcnbmp_ino) || is_bad_inode(vol->lcnbmp_ino)) {
                if (!IS_ERR(vol->lcnbmp_ino))
                        iput(vol->lcnbmp_ino);
                goto bitmap_failed;
        }
        lockdep_set_class(&NTFS_I(vol->lcnbmp_ino)->runlist.lock,
                           &lcnbmp_runlist_lock_key);
        lockdep_set_class(&NTFS_I(vol->lcnbmp_ino)->mrec_lock,
                           &lcnbmp_mrec_lock_key);

        NInoSetSparseDisabled(NTFS_I(vol->lcnbmp_ino));
        if ((vol->nr_clusters + 7) >> 3 > i_size_read(vol->lcnbmp_ino)) {
                iput(vol->lcnbmp_ino);
bitmap_failed:
                ntfs_error(sb, "Failed to load $Bitmap.");
                goto iput_attrdef_err_out;
        }
        /*
         * Get the volume inode and setup our cache of the volume flags and
         * version.
         */
        vol->vol_ino = ntfs_iget(sb, FILE_Volume);
        if (IS_ERR(vol->vol_ino) || is_bad_inode(vol->vol_ino)) {
                if (!IS_ERR(vol->vol_ino))
                        iput(vol->vol_ino);
volume_failed:
                ntfs_error(sb, "Failed to load $Volume.");
                goto iput_lcnbmp_err_out;
        }
        m = map_mft_record(NTFS_I(vol->vol_ino));
        if (IS_ERR(m)) {
iput_volume_failed:
                iput(vol->vol_ino);
                goto volume_failed;
        }
        if (!(ctx = ntfs_attr_get_search_ctx(NTFS_I(vol->vol_ino), m))) {
                ntfs_error(sb, "Failed to get attribute search context.");
                goto get_ctx_vol_failed;
        }
        if (ntfs_attr_lookup(AT_VOLUME_INFORMATION, NULL, 0, 0, 0, NULL, 0,
                        ctx) || ctx->attr->non_resident || ctx->attr->flags) {
err_put_vol:
                ntfs_attr_put_search_ctx(ctx);
get_ctx_vol_failed:
                unmap_mft_record(NTFS_I(vol->vol_ino));
                goto iput_volume_failed;
        }
        vi = (VOLUME_INFORMATION*)((char*)ctx->attr +
                        le16_to_cpu(ctx->attr->data.resident.value_offset));
        /* Some bounds checks. */
        if ((u8*)vi < (u8*)ctx->attr || (u8*)vi +
                        le32_to_cpu(ctx->attr->data.resident.value_length) >
                        (u8*)ctx->attr + le32_to_cpu(ctx->attr->length))
                goto err_put_vol;
        /* Copy the volume flags and version to the ntfs_volume structure. */
        vol->vol_flags = vi->flags;
        vol->major_ver = vi->major_ver;
        vol->minor_ver = vi->minor_ver;
        ntfs_attr_put_search_ctx(ctx);
        unmap_mft_record(NTFS_I(vol->vol_ino));
        printk(KERN_INFO "NTFS volume version %i.%i.\n", vol->major_ver,
                        vol->minor_ver);
        if (vol->major_ver < 3 && NVolSparseEnabled(vol)) {
                ntfs_warning(vol->sb, "Disabling sparse support due to NTFS "
                                "volume version %i.%i (need at least version "
                                "3.0).", vol->major_ver, vol->minor_ver);
                NVolClearSparseEnabled(vol);
        }
#ifdef NTFS_RW
        /* Make sure that no unsupported volume flags are set. */
        if (vol->vol_flags & VOLUME_MUST_MOUNT_RO_MASK) {
                static const char *es1a = "Volume is dirty";
                static const char *es1b = "Volume has been modified by chkdsk";
                static const char *es1c = "Volume has unsupported flags set";
                static const char *es2a = ".  Run chkdsk and mount in Windows.";
                static const char *es2b = ".  Mount in Windows.";
                const char *es1, *es2;

                es2 = es2a;
                if (vol->vol_flags & VOLUME_IS_DIRTY)
                        es1 = es1a;
                else if (vol->vol_flags & VOLUME_MODIFIED_BY_CHKDSK) {
                        es1 = es1b;
                        es2 = es2b;
                } else {
                        es1 = es1c;
                        ntfs_warning(sb, "Unsupported volume flags 0x%x "
                                        "encountered.",
                                        (unsigned)le16_to_cpu(vol->vol_flags));
                }
                /* If a read-write mount, convert it to a read-only mount. */
                if (!(sb->s_flags & MS_RDONLY)) {
                        if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
                                        ON_ERRORS_CONTINUE))) {
                                ntfs_error(sb, "%s and neither on_errors="
                                                "continue nor on_errors="
                                                "remount-ro was specified%s",
                                                es1, es2);
                                goto iput_vol_err_out;
                        }
                        sb->s_flags |= MS_RDONLY;
                        ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
                } else
                        ntfs_warning(sb, "%s.  Will not be able to remount "
                                        "read-write%s", es1, es2);
                /*
                 * Do not set NVolErrors() because ntfs_remount() re-checks the
                 * flags which we need to do in case any flags have changed.
                 */
        }
        /*
         * Get the inode for the logfile, check it and determine if the volume
         * was shutdown cleanly.
         */
        rp = NULL;
        if (!load_and_check_logfile(vol, &rp) ||
                        !ntfs_is_logfile_clean(vol->logfile_ino, rp)) {
                static const char *es1a = "Failed to load $LogFile";
                static const char *es1b = "$LogFile is not clean";
                static const char *es2 = ".  Mount in Windows.";
                const char *es1;

                es1 = !vol->logfile_ino ? es1a : es1b;
                /* If a read-write mount, convert it to a read-only mount. */
                if (!(sb->s_flags & MS_RDONLY)) {
                        if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
                                        ON_ERRORS_CONTINUE))) {
                                ntfs_error(sb, "%s and neither on_errors="
                                                "continue nor on_errors="
                                                "remount-ro was specified%s",
                                                es1, es2);
                                if (vol->logfile_ino) {
                                        BUG_ON(!rp);
                                        ntfs_free(rp);
                                }
                                goto iput_logfile_err_out;
                        }
                        sb->s_flags |= MS_RDONLY;
                        ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
                } else
                        ntfs_warning(sb, "%s.  Will not be able to remount "
                                        "read-write%s", es1, es2);
                /* This will prevent a read-write remount. */
                NVolSetErrors(vol);
        }
        ntfs_free(rp);
#endif /* NTFS_RW */
        /* Get the root directory inode so we can do path lookups. */
        vol->root_ino = ntfs_iget(sb, FILE_root);
        if (IS_ERR(vol->root_ino) || is_bad_inode(vol->root_ino)) {
                if (!IS_ERR(vol->root_ino))
                        iput(vol->root_ino);
                ntfs_error(sb, "Failed to load root directory.");
                goto iput_logfile_err_out;
        }
#ifdef NTFS_RW
        /*
         * Check if Windows is suspended to disk on the target volume.  If it
         * is hibernated, we must not write *anything* to the disk so set
         * NVolErrors() without setting the dirty volume flag and mount
         * read-only.  This will prevent read-write remounting and it will also
         * prevent all writes.
         */
        err = check_windows_hibernation_status(vol);
        if (unlikely(err)) {
                static const char *es1a = "Failed to determine if Windows is "
                                "hibernated";
                static const char *es1b = "Windows is hibernated";
                static const char *es2 = ".  Run chkdsk.";
                const char *es1;

                es1 = err < 0 ? es1a : es1b;
                /* If a read-write mount, convert it to a read-only mount. */
                if (!(sb->s_flags & MS_RDONLY)) {
                        if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
                                        ON_ERRORS_CONTINUE))) {
                                ntfs_error(sb, "%s and neither on_errors="
                                                "continue nor on_errors="
                                                "remount-ro was specified%s",
                                                es1, es2);
                                goto iput_root_err_out;
                        }
                        sb->s_flags |= MS_RDONLY;
                        ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
                } else
                        ntfs_warning(sb, "%s.  Will not be able to remount "
                                        "read-write%s", es1, es2);
                /* This will prevent a read-write remount. */
                NVolSetErrors(vol);

        }
        /* If (still) a read-write mount, mark the volume dirty. */
        if (!(sb->s_flags & MS_RDONLY) &&
                        ntfs_set_volume_flags(vol, VOLUME_IS_DIRTY)) {
                static const char *es1 = "Failed to set dirty bit in volume "
                                "information flags";
                static const char *es2 = ".  Run chkdsk.";

                /* Convert to a read-only mount. */
                if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
                                ON_ERRORS_CONTINUE))) {
                        ntfs_error(sb, "%s and neither on_errors=continue nor "
                                        "on_errors=remount-ro was specified%s",
                                        es1, es2);
                        goto iput_root_err_out;
                }
                ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
                sb->s_flags |= MS_RDONLY;
                /*
                 * Do not set NVolErrors() because ntfs_remount() might manage
                 * to set the dirty flag in which case all would be well.
                 */
        }
#if 0
        // TODO: Enable this code once we start modifying anything that is
        //       different between NTFS 1.2 and 3.x...
        /*
         * If (still) a read-write mount, set the NT4 compatibility flag on
         * newer NTFS version volumes.
         */
        if (!(sb->s_flags & MS_RDONLY) && (vol->major_ver > 1) &&
                        ntfs_set_volume_flags(vol, VOLUME_MOUNTED_ON_NT4)) {
                static const char *es1 = "Failed to set NT4 compatibility flag";
                static const char *es2 = ".  Run chkdsk.";

                /* Convert to a read-only mount. */
                if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
                                ON_ERRORS_CONTINUE))) {
                        ntfs_error(sb, "%s and neither on_errors=continue nor "
                                        "on_errors=remount-ro was specified%s",
                                        es1, es2);
                        goto iput_root_err_out;
                }
                ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
                sb->s_flags |= MS_RDONLY;
                NVolSetErrors(vol);
        }
#endif
        /* If (still) a read-write mount, empty the logfile. */
        if (!(sb->s_flags & MS_RDONLY) &&
                        !ntfs_empty_logfile(vol->logfile_ino)) {
                static const char *es1 = "Failed to empty $LogFile";
                static const char *es2 = ".  Mount in Windows.";

                /* Convert to a read-only mount. */
                if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
                                ON_ERRORS_CONTINUE))) {
                        ntfs_error(sb, "%s and neither on_errors=continue nor "
                                        "on_errors=remount-ro was specified%s",
                                        es1, es2);
                        goto iput_root_err_out;
                }
                ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
                sb->s_flags |= MS_RDONLY;
                NVolSetErrors(vol);
        }
#endif /* NTFS_RW */
        /* If on NTFS versions before 3.0, we are done. */
        if (unlikely(vol->major_ver < 3))
                return true;
        /* NTFS 3.0+ specific initialization. */
        /* Get the security descriptors inode. */
        vol->secure_ino = ntfs_iget(sb, FILE_Secure);
        if (IS_ERR(vol->secure_ino) || is_bad_inode(vol->secure_ino)) {
                if (!IS_ERR(vol->secure_ino))
                        iput(vol->secure_ino);
                ntfs_error(sb, "Failed to load $Secure.");
                goto iput_root_err_out;
        }
        // TODO: Initialize security.
        /* Get the extended system files' directory inode. */
        vol->extend_ino = ntfs_iget(sb, FILE_Extend);
        if (IS_ERR(vol->extend_ino) || is_bad_inode(vol->extend_ino)) {
                if (!IS_ERR(vol->extend_ino))
                        iput(vol->extend_ino);
                ntfs_error(sb, "Failed to load $Extend.");
                goto iput_sec_err_out;
        }
#ifdef NTFS_RW
        /* Find the quota file, load it if present, and set it up. */
        if (!load_and_init_quota(vol)) {
                static const char *es1 = "Failed to load $Quota";
                static const char *es2 = ".  Run chkdsk.";

                /* If a read-write mount, convert it to a read-only mount. */
                if (!(sb->s_flags & MS_RDONLY)) {
                        if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
                                        ON_ERRORS_CONTINUE))) {
                                ntfs_error(sb, "%s and neither on_errors="
                                                "continue nor on_errors="
                                                "remount-ro was specified%s",
                                                es1, es2);
                                goto iput_quota_err_out;
                        }
                        sb->s_flags |= MS_RDONLY;
                        ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
                } else
                        ntfs_warning(sb, "%s.  Will not be able to remount "
                                        "read-write%s", es1, es2);
                /* This will prevent a read-write remount. */
                NVolSetErrors(vol);
        }
        /* If (still) a read-write mount, mark the quotas out of date. */
        if (!(sb->s_flags & MS_RDONLY) &&
                        !ntfs_mark_quotas_out_of_date(vol)) {
                static const char *es1 = "Failed to mark quotas out of date";
                static const char *es2 = ".  Run chkdsk.";

                /* Convert to a read-only mount. */
                if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
                                ON_ERRORS_CONTINUE))) {
                        ntfs_error(sb, "%s and neither on_errors=continue nor "
                                        "on_errors=remount-ro was specified%s",
                                        es1, es2);
                        goto iput_quota_err_out;
                }
                ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
                sb->s_flags |= MS_RDONLY;
                NVolSetErrors(vol);
        }
        /*
         * Find the transaction log file ($UsnJrnl), load it if present, check
         * it, and set it up.
         */
        if (!load_and_init_usnjrnl(vol)) {
                static const char *es1 = "Failed to load $UsnJrnl";
                static const char *es2 = ".  Run chkdsk.";

                /* If a read-write mount, convert it to a read-only mount. */
                if (!(sb->s_flags & MS_RDONLY)) {
                        if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
                                        ON_ERRORS_CONTINUE))) {
                                ntfs_error(sb, "%s and neither on_errors="
                                                "continue nor on_errors="
                                                "remount-ro was specified%s",
                                                es1, es2);
                                goto iput_usnjrnl_err_out;
                        }
                        sb->s_flags |= MS_RDONLY;
                        ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
                } else
                        ntfs_warning(sb, "%s.  Will not be able to remount "
                                        "read-write%s", es1, es2);
                /* This will prevent a read-write remount. */
                NVolSetErrors(vol);
        }
        /* If (still) a read-write mount, stamp the transaction log. */
        if (!(sb->s_flags & MS_RDONLY) && !ntfs_stamp_usnjrnl(vol)) {
                static const char *es1 = "Failed to stamp transaction log "
                                "($UsnJrnl)";
                static const char *es2 = ".  Run chkdsk.";

                /* Convert to a read-only mount. */
                if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
                                ON_ERRORS_CONTINUE))) {
                        ntfs_error(sb, "%s and neither on_errors=continue nor "
                                        "on_errors=remount-ro was specified%s",
                                        es1, es2);
                        goto iput_usnjrnl_err_out;
                }
                ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
                sb->s_flags |= MS_RDONLY;
                NVolSetErrors(vol);
        }
#endif /* NTFS_RW */
        return true;
#ifdef NTFS_RW
iput_usnjrnl_err_out:
        if (vol->usnjrnl_j_ino)
                iput(vol->usnjrnl_j_ino);
        if (vol->usnjrnl_max_ino)
                iput(vol->usnjrnl_max_ino);
        if (vol->usnjrnl_ino)
                iput(vol->usnjrnl_ino);
iput_quota_err_out:
        if (vol->quota_q_ino)
                iput(vol->quota_q_ino);
        if (vol->quota_ino)
                iput(vol->quota_ino);
        iput(vol->extend_ino);
#endif /* NTFS_RW */
iput_sec_err_out:
        iput(vol->secure_ino);
iput_root_err_out:
        iput(vol->root_ino);
iput_logfile_err_out:
#ifdef NTFS_RW
        if (vol->logfile_ino)
                iput(vol->logfile_ino);
iput_vol_err_out:
#endif /* NTFS_RW */
        iput(vol->vol_ino);
iput_lcnbmp_err_out:
        iput(vol->lcnbmp_ino);
iput_attrdef_err_out:
        vol->attrdef_size = 0;
        if (vol->attrdef) {
                ntfs_free(vol->attrdef);
                vol->attrdef = NULL;
        }
#ifdef NTFS_RW
iput_upcase_err_out:
#endif /* NTFS_RW */
        vol->upcase_len = 0;
        mutex_lock(&ntfs_lock);
        if (vol->upcase == default_upcase) {
                ntfs_nr_upcase_users--;
                vol->upcase = NULL;
        }
        mutex_unlock(&ntfs_lock);
        if (vol->upcase) {
                ntfs_free(vol->upcase);
                vol->upcase = NULL;
        }
iput_mftbmp_err_out:
        iput(vol->mftbmp_ino);
iput_mirr_err_out:
#ifdef NTFS_RW
        if (vol->mftmirr_ino)
                iput(vol->mftmirr_ino);
#endif /* NTFS_RW */
        return false;
}

/**
 * ntfs_put_super - called by the vfs to unmount a volume
 * @sb:         vfs superblock of volume to unmount
 *
 * ntfs_put_super() is called by the VFS (from fs/super.c::do_umount()) when
 * the volume is being unmounted (umount system call has been invoked) and it
 * releases all inodes and memory belonging to the NTFS specific part of the
 * super block.
 */
static void ntfs_put_super(struct super_block *sb)
{
        ntfs_volume *vol = NTFS_SB(sb);

        ntfs_debug("Entering.");
#ifdef NTFS_RW
        /*
         * Commit all inodes while they are still open in case some of them
         * cause others to be dirtied.
         */
        ntfs_commit_inode(vol->vol_ino);

        /* NTFS 3.0+ specific. */
        if (vol->major_ver >= 3) {
                if (vol->usnjrnl_j_ino)
                        ntfs_commit_inode(vol->usnjrnl_j_ino);
                if (vol->usnjrnl_max_ino)
                        ntfs_commit_inode(vol->usnjrnl_max_ino);
                if (vol->usnjrnl_ino)
                        ntfs_commit_inode(vol->usnjrnl_ino);
                if (vol->quota_q_ino)
                        ntfs_commit_inode(vol->quota_q_ino);
                if (vol->quota_ino)
                        ntfs_commit_inode(vol->quota_ino);
                if (vol->extend_ino)
                        ntfs_commit_inode(vol->extend_ino);
                if (vol->secure_ino)
                        ntfs_commit_inode(vol->secure_ino);
        }

        ntfs_commit_inode(vol->root_ino);

        down_write(&vol->lcnbmp_lock);
        ntfs_commit_inode(vol->lcnbmp_ino);
        up_write(&vol->lcnbmp_lock);

        down_write(&vol->mftbmp_lock);
        ntfs_commit_inode(vol->mftbmp_ino);
        up_write(&vol->mftbmp_lock);

        if (vol->logfile_ino)
                ntfs_commit_inode(vol->logfile_ino);

        if (vol->mftmirr_ino)
                ntfs_commit_inode(vol->mftmirr_ino);
        ntfs_commit_inode(vol->mft_ino);

        /*
         * If a read-write mount and no volume errors have occured, mark the
         * volume clean.  Also, re-commit all affected inodes.
         */
        if (!(sb->s_flags & MS_RDONLY)) {
                if (!NVolErrors(vol)) {
                        if (ntfs_clear_volume_flags(vol, VOLUME_IS_DIRTY))
                                ntfs_warning(sb, "Failed to clear dirty bit "
                                                "in volume information "
                                                "flags.  Run chkdsk.");
                        ntfs_commit_inode(vol->vol_ino);
                        ntfs_commit_inode(vol->root_ino);
                        if (vol->mftmirr_ino)
                                ntfs_commit_inode(vol->mftmirr_ino);
                        ntfs_commit_inode(vol->mft_ino);
                } else {
                        ntfs_warning(sb, "Volume has errors.  Leaving volume "
                                        "marked dirty.  Run chkdsk.");
                }
        }
#endif /* NTFS_RW */

        iput(vol->vol_ino);
        vol->vol_ino = NULL;

        /* NTFS 3.0+ specific clean up. */
        if (vol->major_ver >= 3) {
#ifdef NTFS_RW
                if (vol->usnjrnl_j_ino) {
                        iput(vol->usnjrnl_j_ino);
                        vol->usnjrnl_j_ino = NULL;
                }
                if (vol->usnjrnl_max_ino) {
                        iput(vol->usnjrnl_max_ino);
                        vol->usnjrnl_max_ino = NULL;
                }
                if (vol->usnjrnl_ino) {
                        iput(vol->usnjrnl_ino);
                        vol->usnjrnl_ino = NULL;
                }
                if (vol->quota_q_ino) {
                        iput(vol->quota_q_ino);
                        vol->quota_q_ino = NULL;
                }
                if (vol->quota_ino) {
                        iput(vol->quota_ino);
                        vol->quota_ino = NULL;
                }
#endif /* NTFS_RW */
                if (vol->extend_ino) {
                        iput(vol->extend_ino);
                        vol->extend_ino = NULL;
                }
                if (vol->secure_ino) {
                        iput(vol->secure_ino);
                        vol->secure_ino = NULL;
                }
        }

        iput(vol->root_ino);
        vol->root_ino = NULL;

        down_write(&vol->lcnbmp_lock);
        iput(vol->lcnbmp_ino);
        vol->lcnbmp_ino = NULL;
        up_write(&vol->lcnbmp_lock);

        down_write(&vol->mftbmp_lock);
        iput(vol->mftbmp_ino);
        vol->mftbmp_ino = NULL;
        up_write(&vol->mftbmp_lock);

#ifdef NTFS_RW
        if (vol->logfile_ino) {
                iput(vol->logfile_ino);
                vol->logfile_ino = NULL;
        }
        if (vol->mftmirr_ino) {
                /* Re-commit the mft mirror and mft just in case. */
                ntfs_commit_inode(vol->mftmirr_ino);
                ntfs_commit_inode(vol->mft_ino);
                iput(vol->mftmirr_ino);
                vol->mftmirr_ino = NULL;
        }
        /*
         * If any dirty inodes are left, throw away all mft data page cache
         * pages to allow a clean umount.  This should never happen any more
         * due to mft.c::ntfs_mft_writepage() cleaning all the dirty pages as
         * the underlying mft records are written out and cleaned.  If it does,
         * happen anyway, we want to know...
         */
        ntfs_commit_inode(vol->mft_ino);
        write_inode_now(vol->mft_ino, 1);
        if (sb_has_dirty_inodes(sb)) {
                const char *s1, *s2;

                mutex_lock(&vol->mft_ino->i_mutex);
                truncate_inode_pages(vol->mft_ino->i_mapping, 0);
                mutex_unlock(&vol->mft_ino->i_mutex);
                write_inode_now(vol->mft_ino, 1);
                if (sb_has_dirty_inodes(sb)) {
                        static const char *_s1 = "inodes";
                        static const char *_s2 = "";
                        s1 = _s1;
                        s2 = _s2;
                } else {
                        static const char *_s1 = "mft pages";
                        static const char *_s2 = "They have been thrown "
                                        "away.  ";
                        s1 = _s1;
                        s2 = _s2;
                }
                ntfs_error(sb, "Dirty %s found at umount time.  %sYou should "
                                "run chkdsk.  Please email "
                                "linux-ntfs-dev@lists.sourceforge.net and say "
                                "that you saw this message.  Thank you.", s1,
                                s2);
        }
#endif /* NTFS_RW */

        iput(vol->mft_ino);
        vol->mft_ino = NULL;

        /* Throw away the table of attribute definitions. */
        vol->attrdef_size = 0;
        if (vol->attrdef) {
                ntfs_free(vol->attrdef);
                vol->attrdef = NULL;
        }
        vol->upcase_len = 0;
        /*
         * Destroy the global default upcase table if necessary.  Also decrease
         * the number of upcase users if we are a user.
         */
        mutex_lock(&ntfs_lock);
        if (vol->upcase == default_upcase) {
                ntfs_nr_upcase_users--;
                vol->upcase = NULL;
        }
        if (!ntfs_nr_upcase_users && default_upcase) {
                ntfs_free(default_upcase);
                default_upcase = NULL;
        }
        if (vol->cluster_size <= 4096 && !--ntfs_nr_compression_users)
                free_compression_buffers();
        mutex_unlock(&ntfs_lock);
        if (vol->upcase) {
                ntfs_free(vol->upcase);
                vol->upcase = NULL;
        }
        if (vol->nls_map) {
                unload_nls(vol->nls_map);
                vol->nls_map = NULL;
        }
        sb->s_fs_info = NULL;
        kfree(vol);
        return;
}

/**
 * get_nr_free_clusters - return the number of free clusters on a volume
 * @vol:        ntfs volume for which to obtain free cluster count
 *
 * Calculate the number of free clusters on the mounted NTFS volume @vol. We
 * actually calculate the number of clusters in use instead because this
 * allows us to not care about partial pages as these will be just zero filled
 * and hence not be counted as allocated clusters.
 *
 * The only particularity is that clusters beyond the end of the logical ntfs
 * volume will be marked as allocated to prevent errors which means we have to
 * discount those at the end. This is important as the cluster bitmap always
 * has a size in multiples of 8 bytes, i.e. up to 63 clusters could be outside
 * the logical volume and marked in use when they are not as they do not exist.
 *
 * If any pages cannot be read we assume all clusters in the erroring pages are
 * in use. This means we return an underestimate on errors which is better than
 * an overestimate.
 */
static s64 get_nr_free_clusters(ntfs_volume *vol)
{
        s64 nr_free = vol->nr_clusters;
        u32 *kaddr;
        struct address_space *mapping = vol->lcnbmp_ino->i_mapping;
        struct page *page;
        pgoff_t index, max_index;

        ntfs_debug("Entering.");
        /* Serialize accesses to the cluster bitmap. */
        down_read(&vol->lcnbmp_lock);
        /*
         * Convert the number of bits into bytes rounded up, then convert into
         * multiples of PAGE_CACHE_SIZE, rounding up so that if we have one
         * full and one partial page max_index = 2.
         */
        max_index = (((vol->nr_clusters + 7) >> 3) + PAGE_CACHE_SIZE - 1) >>
                        PAGE_CACHE_SHIFT;
        /* Use multiples of 4 bytes, thus max_size is PAGE_CACHE_SIZE / 4. */
        ntfs_debug("Reading $Bitmap, max_index = 0x%lx, max_size = 0x%lx.",
                        max_index, PAGE_CACHE_SIZE / 4);
        for (index = 0; index < max_index; index++) {
                unsigned int i;
                /*
                 * Read the page from page cache, getting it from backing store
                 * if necessary, and increment the use count.
                 */
                page = read_mapping_page(mapping, index, NULL);
                /* Ignore pages which errored synchronously. */
                if (IS_ERR(page)) {
                        ntfs_debug("read_mapping_page() error. Skipping "
                                        "page (index 0x%lx).", index);
                        nr_free -= PAGE_CACHE_SIZE * 8;
                        continue;
                }
                kaddr = (u32*)kmap_atomic(page, KM_USER0);
                /*
                 * For each 4 bytes, subtract the number of set bits. If this
                 * is the last page and it is partial we don't really care as
                 * it just means we do a little extra work but it won't affect
                 * the result as all out of range bytes are set to zero by
                 * ntfs_readpage().
                 */
                for (i = 0; i < PAGE_CACHE_SIZE / 4; i++)
                        nr_free -= (s64)hweight32(kaddr[i]);
                kunmap_atomic(kaddr, KM_USER0);
                page_cache_release(page);
        }
        ntfs_debug("Finished reading $Bitmap, last index = 0x%lx.", index - 1);
        /*
         * Fixup for eventual bits outside logical ntfs volume (see function
         * description above).
         */
        if (vol->nr_clusters & 63)
                nr_free += 64 - (vol->nr_clusters & 63);
        up_read(&vol->lcnbmp_lock);
        /* If errors occured we may well have gone below zero, fix this. */
        if (nr_free < 0)
                nr_free = 0;
        ntfs_debug("Exiting.");
        return nr_free;
}

/**
 * __get_nr_free_mft_records - return the number of free inodes on a volume
 * @vol:        ntfs volume for which to obtain free inode count
 * @nr_free:    number of mft records in filesystem
 * @max_index:  maximum number of pages containing set bits
 *
 * Calculate the number of free mft records (inodes) on the mounted NTFS
 * volume @vol. We actually calculate the number of mft records in use instead
 * because this allows us to not care about partial pages as these will be just
 * zero filled and hence not be counted as allocated mft record.
 *
 * If any pages cannot be read we assume all mft records in the erroring pages
 * are in use. This means we return an underestimate on errors which is better
 * than an overestimate.
 *
 * NOTE: Caller must hold mftbmp_lock rw_semaphore for reading or writing.
 */
static unsigned long __get_nr_free_mft_records(ntfs_volume *vol,
                s64 nr_free, const pgoff_t max_index)
{
        u32 *kaddr;
        struct address_space *mapping = vol->mftbmp_ino->i_mapping;
        struct page *page;
        pgoff_t index;

        ntfs_debug("Entering.");
        /* Use multiples of 4 bytes, thus max_size is PAGE_CACHE_SIZE / 4. */
        ntfs_debug("Reading $MFT/$BITMAP, max_index = 0x%lx, max_size = "
                        "0x%lx.", max_index, PAGE_CACHE_SIZE / 4);
        for (index = 0; index < max_index; index++) {
                unsigned int i;
                /*
                 * Read the page from page cache, getting it from backing store
                 * if necessary, and increment the use count.
                 */
                page = read_mapping_page(mapping, index, NULL);
                /* Ignore pages which errored synchronously. */
                if (IS_ERR(page)) {
                        ntfs_debug("read_mapping_page() error. Skipping "
                                        "page (index 0x%lx).", index);
                        nr_free -= PAGE_CACHE_SIZE * 8;
                        continue;
                }
                kaddr = (u32*)kmap_atomic(page, KM_USER0);
                /*
                 * For each 4 bytes, subtract the number of set bits. If this
                 * is the last page and it is partial we don't really care as
                 * it just means we do a little extra work but it won't affect
                 * the result as all out of range bytes are set to zero by
                 * ntfs_readpage().
                 */
                for (i = 0; i < PAGE_CACHE_SIZE / 4; i++)
                        nr_free -= (s64)hweight32(kaddr[i]);
                kunmap_atomic(kaddr, KM_USER0);
                page_cache_release(page);
        }
        ntfs_debug("Finished reading $MFT/$BITMAP, last index = 0x%lx.",
                        index - 1);
        /* If errors occured we may well have gone below zero, fix this. */
        if (nr_free < 0)
                nr_free = 0;
        ntfs_debug("Exiting.");
        return nr_free;
}

/**
 * ntfs_statfs - return information about mounted NTFS volume
 * @dentry:     dentry from mounted volume
 * @sfs:        statfs structure in which to return the information
 *
 * Return information about the mounted NTFS volume @dentry in the statfs structure
 * pointed to by @sfs (this is initialized with zeros before ntfs_statfs is
 * called). We interpret the values to be correct of the moment in time at
 * which we are called. Most values are variable otherwise and this isn't just
 * the free values but the totals as well. For example we can increase the
 * total number of file nodes if we run out and we can keep doing this until
 * there is no more space on the volume left at all.
 *
 * Called from vfs_statfs which is used to handle the statfs, fstatfs, and
 * ustat system calls.
 *
 * Return 0 on success or -errno on error.
 */
static int ntfs_statfs(struct dentry *dentry, struct kstatfs *sfs)
{
        struct super_block *sb = dentry->d_sb;
        s64 size;
        ntfs_volume *vol = NTFS_SB(sb);
        ntfs_inode *mft_ni = NTFS_I(vol->mft_ino);
        pgoff_t max_index;
        unsigned long flags;

        ntfs_debug("Entering.");
        /* Type of filesystem. */
        sfs->f_type   = NTFS_SB_MAGIC;
        /* Optimal transfer block size. */
        sfs->f_bsize  = PAGE_CACHE_SIZE;
        /*
         * Total data blocks in filesystem in units of f_bsize and since
         * inodes are also stored in data blocs ($MFT is a file) this is just
         * the total clusters.
         */
        sfs->f_blocks = vol->nr_clusters << vol->cluster_size_bits >>
                                PAGE_CACHE_SHIFT;
        /* Free data blocks in filesystem in units of f_bsize. */
        size          = get_nr_free_clusters(vol) << vol->cluster_size_bits >>
                                PAGE_CACHE_SHIFT;
        if (size < 0LL)
                size = 0LL;
        /* Free blocks avail to non-superuser, same as above on NTFS. */
        sfs->f_bavail = sfs->f_bfree = size;
        /* Serialize accesses to the inode bitmap. */
        down_read(&vol->mftbmp_lock);
        read_lock_irqsave(&mft_ni->size_lock, flags);
        size = i_size_read(vol->mft_ino) >> vol->mft_record_size_bits;
        /*
         * Convert the maximum number of set bits into bytes rounded up, then
         * convert into multiples of PAGE_CACHE_SIZE, rounding up so that if we
         * have one full and one partial page max_index = 2.
         */
        max_index = ((((mft_ni->initialized_size >> vol->mft_record_size_bits)
                        + 7) >> 3) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
        read_unlock_irqrestore(&mft_ni->size_lock, flags);
        /* Number of inodes in filesystem (at this point in time). */
        sfs->f_files = size;
        /* Free inodes in fs (based on current total count). */
        sfs->f_ffree = __get_nr_free_mft_records(vol, size, max_index);
        up_read(&vol->mftbmp_lock);
        /*
         * File system id. This is extremely *nix flavour dependent and even
         * within Linux itself all fs do their own thing. I interpret this to
         * mean a unique id associated with the mounted fs and not the id
         * associated with the filesystem driver, the latter is already given
         * by the filesystem type in sfs->f_type. Thus we use the 64-bit
         * volume serial number splitting it into two 32-bit parts. We enter
         * the least significant 32-bits in f_fsid[0] and the most significant
         * 32-bits in f_fsid[1].
         */
        sfs->f_fsid.val[0] = vol->serial_no & 0xffffffff;
        sfs->f_fsid.val[1] = (vol->serial_no >> 32) & 0xffffffff;
        /* Maximum length of filenames. */
        sfs->f_namelen     = NTFS_MAX_NAME_LEN;
        return 0;
}

/**
 * The complete super operations.
 */
static const struct super_operations ntfs_sops = {
        .alloc_inode    = ntfs_alloc_big_inode,   /* VFS: Allocate new inode. */
        .destroy_inode  = ntfs_destroy_big_inode, /* VFS: Deallocate inode. */
#ifdef NTFS_RW
        //.dirty_inode  = NULL,                 /* VFS: Called from
        //                                         __mark_inode_dirty(). */
        .write_inode    = ntfs_write_inode,     /* VFS: Write dirty inode to
                                                   disk. */
        //.drop_inode   = NULL,                 /* VFS: Called just after the
        //                                         inode reference count has
        //                                         been decreased to zero.
        //                                         NOTE: The inode lock is
        //                                         held. See fs/inode.c::
        //                                         generic_drop_inode(). */
        //.delete_inode = NULL,                 /* VFS: Delete inode from disk.
        //                                         Called when i_count becomes
        //                                         0 and i_nlink is also 0. */
        //.write_super  = NULL,                 /* Flush dirty super block to
        //                                         disk. */
        //.sync_fs      = NULL,                 /* ? */
        //.write_super_lockfs   = NULL,         /* ? */
        //.unlockfs     = NULL,                 /* ? */
#endif /* NTFS_RW */
        .put_super      = ntfs_put_super,       /* Syscall: umount. */
        .statfs         = ntfs_statfs,          /* Syscall: statfs */
        .remount_fs     = ntfs_remount,         /* Syscall: mount -o remount. */
        .clear_inode    = ntfs_clear_big_inode, /* VFS: Called when an inode is
                                                   removed from memory. */
        //.umount_begin = NULL,                 /* Forced umount. */
        .show_options   = ntfs_show_options,    /* Show mount options in
                                                   proc. */
};

/**
 * ntfs_fill_super - mount an ntfs filesystem
 * @sb:         super block of ntfs filesystem to mount
 * @opt:        string containing the mount options
 * @silent:     silence error output
 *
 * ntfs_fill_super() is called by the VFS to mount the device described by @sb
 * with the mount otions in @data with the NTFS filesystem.
 *
 * If @silent is true, remain silent even if errors are detected. This is used
 * during bootup, when the kernel tries to mount the root filesystem with all
 * registered filesystems one after the other until one succeeds. This implies
 * that all filesystems except the correct one will quite correctly and
 * expectedly return an error, but nobody wants to see error messages when in
 * fact this is what is supposed to happen.
 *
 * NOTE: @sb->s_flags contains the mount options flags.
 */
static int ntfs_fill_super(struct super_block *sb, void *opt, const int silent)
{
        ntfs_volume *vol;
        struct buffer_head *bh;
        struct inode *tmp_ino;
        int blocksize, result;

        /*
         * We do a pretty difficult piece of bootstrap by reading the
         * MFT (and other metadata) from disk into memory. We'll only
         * release this metadata during umount, so the locking patterns
         * observed during bootstrap do not count. So turn off the
         * observation of locking patterns (strictly for this context
         * only) while mounting NTFS. [The validator is still active
         * otherwise, even for this context: it will for example record
         * lock class registrations.]
         */
        lockdep_off();
        ntfs_debug("Entering.");
#ifndef NTFS_RW
        sb->s_flags |= MS_RDONLY;
#endif /* ! NTFS_RW */
        /* Allocate a new ntfs_volume and place it in sb->s_fs_info. */
        sb->s_fs_info = kmalloc(sizeof(ntfs_volume), GFP_NOFS);
        vol = NTFS_SB(sb);
        if (!vol) {
                if (!silent)
                        ntfs_error(sb, "Allocation of NTFS volume structure "
                                        "failed. Aborting mount...");
                lockdep_on();
                return -ENOMEM;
        }
        /* Initialize ntfs_volume structure. */
        *vol = (ntfs_volume) {
                .sb = sb,
                /*
                 * Default is group and other don't have any access to files or
                 * directories while owner has full access. Further, files by
                 * default are not executable but directories are of course
                 * browseable.
                 */
                .fmask = 0177,
                .dmask = 0077,
        };
        init_rwsem(&vol->mftbmp_lock);
        init_rwsem(&vol->lcnbmp_lock);

        unlock_kernel();

        /* By default, enable sparse support. */
        NVolSetSparseEnabled(vol);

        /* Important to get the mount options dealt with now. */
        if (!parse_options(vol, (char*)opt))
                goto err_out_now;

        /* We support sector sizes up to the PAGE_CACHE_SIZE. */
        if (bdev_hardsect_size(sb->s_bdev) > PAGE_CACHE_SIZE) {
                if (!silent)
                        ntfs_error(sb, "Device has unsupported sector size "
                                        "(%i).  The maximum supported sector "
                                        "size on this architecture is %lu "
                                        "bytes.",
                                        bdev_hardsect_size(sb->s_bdev),
                                        PAGE_CACHE_SIZE);
                goto err_out_now;
        }
        /*
         * Setup the device access block size to NTFS_BLOCK_SIZE or the hard
         * sector size, whichever is bigger.
         */
        blocksize = sb_min_blocksize(sb, NTFS_BLOCK_SIZE);
        if (blocksize < NTFS_BLOCK_SIZE) {
                if (!silent)
                        ntfs_error(sb, "Unable to set device block size.");
                goto err_out_now;
        }
        BUG_ON(blocksize != sb->s_blocksize);
        ntfs_debug("Set device block size to %i bytes (block size bits %i).",
                        blocksize, sb->s_blocksize_bits);
        /* Determine the size of the device in units of block_size bytes. */
        if (!i_size_read(sb->s_bdev->bd_inode)) {
                if (!silent)
                        ntfs_error(sb, "Unable to determine device size.");
                goto err_out_now;
        }
        vol->nr_blocks = i_size_read(sb->s_bdev->bd_inode) >>
                        sb->s_blocksize_bits;
        /* Read the boot sector and return unlocked buffer head to it. */
        if (!(bh = read_ntfs_boot_sector(sb, silent))) {
                if (!silent)
                        ntfs_error(sb, "Not an NTFS volume.");
                goto err_out_now;
        }
        /*
         * Extract the data from the boot sector and setup the ntfs volume
         * using it.
         */
        result = parse_ntfs_boot_sector(vol, (NTFS_BOOT_SECTOR*)bh->b_data);
        brelse(bh);
        if (!result) {
                if (!silent)
                        ntfs_error(sb, "Unsupported NTFS filesystem.");
                goto err_out_now;
        }
        /*
         * If the boot sector indicates a sector size bigger than the current
         * device block size, switch the device block size to the sector size.
         * TODO: It may be possible to support this case even when the set
         * below fails, we would just be breaking up the i/o for each sector
         * into multiple blocks for i/o purposes but otherwise it should just
         * work.  However it is safer to leave disabled until someone hits this
         * error message and then we can get them to try it without the setting
         * so we know for sure that it works.
         */
        if (vol->sector_size > blocksize) {
                blocksize = sb_set_blocksize(sb, vol->sector_size);
                if (blocksize != vol->sector_size) {
                        if (!silent)
                                ntfs_error(sb, "Unable to set device block "
                                                "size to sector size (%i).",
                                                vol->sector_size);
                        goto err_out_now;
                }
                BUG_ON(blocksize != sb->s_blocksize);
                vol->nr_blocks = i_size_read(sb->s_bdev->bd_inode) >>
                                sb->s_blocksize_bits;
                ntfs_debug("Changed device block size to %i bytes (block size "
                                "bits %i) to match volume sector size.",
                                blocksize, sb->s_blocksize_bits);
        }
        /* Initialize the cluster and mft allocators. */
        ntfs_setup_allocators(vol);
        /* Setup remaining fields in the super block. */
        sb->s_magic = NTFS_SB_MAGIC;
        /*
         * Ntfs allows 63 bits for the file size, i.e. correct would be:
         *      sb->s_maxbytes = ~0ULL >> 1;
         * But the kernel uses a long as the page cache page index which on
         * 32-bit architectures is only 32-bits. MAX_LFS_FILESIZE is kernel
         * defined to the maximum the page cache page index can cope with
         * without overflowing the index or to 2^63 - 1, whichever is smaller.
         */
        sb->s_maxbytes = MAX_LFS_FILESIZE;
        /* Ntfs measures time in 100ns intervals. */
        sb->s_time_gran = 100;
        /*
         * Now load the metadata required for the page cache and our address
         * space operations to function. We do this by setting up a specialised
         * read_inode method and then just calling the normal iget() to obtain
         * the inode for $MFT which is sufficient to allow our normal inode
         * operations and associated address space operations to function.
         */
        sb->s_op = &ntfs_sops;
        tmp_ino = new_inode(sb);
        if (!tmp_ino) {
                if (!silent)
                        ntfs_error(sb, "Failed to load essential metadata.");
                goto err_out_now;
        }
        tmp_ino->i_ino = FILE_MFT;
        insert_inode_hash(tmp_ino);
        if (ntfs_read_inode_mount(tmp_ino) < 0) {
                if (!silent)
                        ntfs_error(sb, "Failed to load essential metadata.");
                goto iput_tmp_ino_err_out_now;
        }
        mutex_lock(&ntfs_lock);
        /*
         * The current mount is a compression user if the cluster size is
         * less than or equal 4kiB.
         */
        if (vol->cluster_size <= 4096 && !ntfs_nr_compression_users++) {
                result = allocate_compression_buffers();
                if (result) {
                        ntfs_error(NULL, "Failed to allocate buffers "
                                        "for compression engine.");
                        ntfs_nr_compression_users--;
                        mutex_unlock(&ntfs_lock);
                        goto iput_tmp_ino_err_out_now;
                }
        }
        /*
         * Generate the global default upcase table if necessary.  Also
         * temporarily increment the number of upcase users to avoid race
         * conditions with concurrent (u)mounts.
         */
        if (!default_upcase)
                default_upcase = generate_default_upcase();
        ntfs_nr_upcase_users++;
        mutex_unlock(&ntfs_lock);
        /*
         * From now on, ignore @silent parameter. If we fail below this line,
         * it will be due to a corrupt fs or a system error, so we report it.
         */
        /*
         * Open the system files with normal access functions and complete
         * setting up the ntfs super block.
         */
        if (!load_system_files(vol)) {
                ntfs_error(sb, "Failed to load system files.");
                goto unl_upcase_iput_tmp_ino_err_out_now;
        }
        if ((sb->s_root = d_alloc_root(vol->root_ino))) {
                /* We increment i_count simulating an ntfs_iget(). */
                atomic_inc(&vol->root_ino->i_count);
                ntfs_debug("Exiting, status successful.");
                /* Release the default upcase if it has no users. */
                mutex_lock(&ntfs_lock);
                if (!--ntfs_nr_upcase_users && default_upcase) {
                        ntfs_free(default_upcase);
                        default_upcase = NULL;
                }
                mutex_unlock(&ntfs_lock);
                sb->s_export_op = &ntfs_export_ops;
                lock_kernel();
                lockdep_on();
                return 0;
        }
        ntfs_error(sb, "Failed to allocate root directory.");
        /* Clean up after the successful load_system_files() call from above. */
        // TODO: Use ntfs_put_super() instead of repeating all this code...
        // FIXME: Should mark the volume clean as the error is most likely
        //        -ENOMEM.
        iput(vol->vol_ino);
        vol->vol_ino = NULL;
        /* NTFS 3.0+ specific clean up. */
        if (vol->major_ver >= 3) {
#ifdef NTFS_RW
                if (vol->usnjrnl_j_ino) {
                        iput(vol->usnjrnl_j_ino);
                        vol->usnjrnl_j_ino = NULL;
                }
                if (vol->usnjrnl_max_ino) {
                        iput(vol->usnjrnl_max_ino);
                        vol->usnjrnl_max_ino = NULL;
                }
                if (vol->usnjrnl_ino) {
                        iput(vol->usnjrnl_ino);
                        vol->usnjrnl_ino = NULL;
                }
                if (vol->quota_q_ino) {
                        iput(vol->quota_q_ino);
                        vol->quota_q_ino = NULL;
                }
                if (vol->quota_ino) {
                        iput(vol->quota_ino);
                        vol->quota_ino = NULL;
                }
#endif /* NTFS_RW */
                if (vol->extend_ino) {
                        iput(vol->extend_ino);
                        vol->extend_ino = NULL;
                }
                if (vol->secure_ino) {
                        iput(vol->secure_ino);
                        vol->secure_ino = NULL;
                }
        }
        iput(vol->root_ino);
        vol->root_ino = NULL;
        iput(vol->lcnbmp_ino);
        vol->lcnbmp_ino = NULL;
        iput(vol->mftbmp_ino);
        vol->mftbmp_ino = NULL;
#ifdef NTFS_RW
        if (vol->logfile_ino) {
                iput(vol->logfile_ino);
                vol->logfile_ino = NULL;
        }