// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 */

#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/seq_file.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/mount.h>
#include <linux/writeback.h>
#include <linux/statfs.h>
#include <linux/compat.h>
#include <linux/parser.h>
#include <linux/ctype.h>
#include <linux/namei.h>
#include <linux/miscdevice.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include <linux/cleancache.h>
#include <linux/ratelimit.h>
#include <linux/crc32c.h>
#include <linux/btrfs.h>
#include "delayed-inode.h"
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "print-tree.h"
#include "props.h"
#include "xattr.h"
#include "volumes.h"
#include "export.h"
#include "compression.h"
#include "rcu-string.h"
#include "dev-replace.h"
#include "free-space-cache.h"
#include "backref.h"
#include "space-info.h"
#include "sysfs.h"
#include "zoned.h"
#include "tests/btrfs-tests.h"
#include "block-group.h"
#include "discard.h"
#include "qgroup.h"
#define CREATE_TRACE_POINTS
#include <trace/events/btrfs.h>

static const struct super_operations btrfs_super_ops;

/*
 * Types for mounting the default subvolume and a subvolume explicitly
 * requested by subvol=/path. That way the callchain is straightforward and we
 * don't have to play tricks with the mount options and recursive calls to
 * btrfs_mount.
 *
 * The new btrfs_root_fs_type also servers as a tag for the bdev_holder.
 */
static struct file_system_type btrfs_fs_type;
static struct file_system_type btrfs_root_fs_type;

static int btrfs_remount(struct super_block *sb, int *flags, char *data);

/*
 * Generally the error codes correspond to their respective errors, but there
 * are a few special cases.
 *
 * EUCLEAN: Any sort of corruption that we encounter.  The tree-checker for
 *          instance will return EUCLEAN if any of the blocks are corrupted in
 *          a way that is problematic.  We want to reserve EUCLEAN for these
 *          sort of corruptions.
 *
 * EROFS: If we check BTRFS_FS_STATE_ERROR and fail out with a return error, we
 *        need to use EROFS for this case.  We will have no idea of the
 *        original failure, that will have been reported at the time we tripped
 *        over the error.  Each subsequent error that doesn't have any context
 *        of the original error should use EROFS when handling BTRFS_FS_STATE_ERROR.
 */
const char * __attribute_const__ btrfs_decode_error(int errno)
{
        char *errstr = "unknown";

        switch (errno) {
        case -ENOENT:           /* -2 */
                errstr = "No such entry";
                break;
        case -EIO:              /* -5 */
                errstr = "IO failure";
                break;
        case -ENOMEM:           /* -12*/
                errstr = "Out of memory";
                break;
        case -EEXIST:           /* -17 */
                errstr = "Object already exists";
                break;
        case -ENOSPC:           /* -28 */
                errstr = "No space left";
                break;
        case -EROFS:            /* -30 */
                errstr = "Readonly filesystem";
                break;
        case -EOPNOTSUPP:       /* -95 */
                errstr = "Operation not supported";
                break;
        case -EUCLEAN:          /* -117 */
                errstr = "Filesystem corrupted";
                break;
        case -EDQUOT:           /* -122 */
                errstr = "Quota exceeded";
                break;
        }

        return errstr;
}

/*
 * __btrfs_handle_fs_error decodes expected errors from the caller and
 * invokes the appropriate error response.
 */
__cold
void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function,
                       unsigned int line, int errno, const char *fmt, ...)
{
        struct super_block *sb = fs_info->sb;
#ifdef CONFIG_PRINTK
        const char *errstr;
#endif

        /*
         * Special case: if the error is EROFS, and we're already
         * under SB_RDONLY, then it is safe here.
         */
        if (errno == -EROFS && sb_rdonly(sb))
                return;

#ifdef CONFIG_PRINTK
        errstr = btrfs_decode_error(errno);
        if (fmt) {
                struct va_format vaf;
                va_list args;

                va_start(args, fmt);
                vaf.fmt = fmt;
                vaf.va = &args;

                pr_crit("BTRFS: error (device %s) in %s:%d: errno=%d %s (%pV)\n",
                        sb->s_id, function, line, errno, errstr, &vaf);
                va_end(args);
        } else {
                pr_crit("BTRFS: error (device %s) in %s:%d: errno=%d %s\n",
                        sb->s_id, function, line, errno, errstr);
        }
#endif

        /*
         * Today we only save the error info to memory.  Long term we'll
         * also send it down to the disk
         */
        set_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state);

        /* Don't go through full error handling during mount */
        if (!(sb->s_flags & SB_BORN))
                return;

        if (sb_rdonly(sb))
                return;

        btrfs_discard_stop(fs_info);

        /* btrfs handle error by forcing the filesystem readonly */
        btrfs_set_sb_rdonly(sb);
        btrfs_info(fs_info, "forced readonly");
        /*
         * Note that a running device replace operation is not canceled here
         * although there is no way to update the progress. It would add the
         * risk of a deadlock, therefore the canceling is omitted. The only
         * penalty is that some I/O remains active until the procedure
         * completes. The next time when the filesystem is mounted writable
         * again, the device replace operation continues.
         */
}

#ifdef CONFIG_PRINTK
static const char * const logtypes[] = {
        "emergency",
        "alert",
        "critical",
        "error",
        "warning",
        "notice",
        "info",
        "debug",
};


/*
 * Use one ratelimit state per log level so that a flood of less important
 * messages doesn't cause more important ones to be dropped.
 */
static struct ratelimit_state printk_limits[] = {
        RATELIMIT_STATE_INIT(printk_limits[0], DEFAULT_RATELIMIT_INTERVAL, 100),
        RATELIMIT_STATE_INIT(printk_limits[1], DEFAULT_RATELIMIT_INTERVAL, 100),
        RATELIMIT_STATE_INIT(printk_limits[2], DEFAULT_RATELIMIT_INTERVAL, 100),
        RATELIMIT_STATE_INIT(printk_limits[3], DEFAULT_RATELIMIT_INTERVAL, 100),
        RATELIMIT_STATE_INIT(printk_limits[4], DEFAULT_RATELIMIT_INTERVAL, 100),
        RATELIMIT_STATE_INIT(printk_limits[5], DEFAULT_RATELIMIT_INTERVAL, 100),
        RATELIMIT_STATE_INIT(printk_limits[6], DEFAULT_RATELIMIT_INTERVAL, 100),
        RATELIMIT_STATE_INIT(printk_limits[7], DEFAULT_RATELIMIT_INTERVAL, 100),
};

void __cold btrfs_printk(const struct btrfs_fs_info *fs_info, const char *fmt, ...)
{
        char lvl[PRINTK_MAX_SINGLE_HEADER_LEN + 1] = "\0";
        struct va_format vaf;
        va_list args;
        int kern_level;
        const char *type = logtypes[4];
        struct ratelimit_state *ratelimit = &printk_limits[4];

        va_start(args, fmt);

        while ((kern_level = printk_get_level(fmt)) != 0) {
                size_t size = printk_skip_level(fmt) - fmt;

                if (kern_level >= '0' && kern_level <= '7') {
                        memcpy(lvl, fmt,  size);
                        lvl[size] = '\0';
                        type = logtypes[kern_level - '0'];
                        ratelimit = &printk_limits[kern_level - '0'];
                }
                fmt += size;
        }

        vaf.fmt = fmt;
        vaf.va = &args;

        if (__ratelimit(ratelimit)) {
                if (fs_info)
                        printk("%sBTRFS %s (device %s): %pV\n", lvl, type,
                                fs_info->sb->s_id, &vaf);
                else
                        printk("%sBTRFS %s: %pV\n", lvl, type, &vaf);
        }

        va_end(args);
}
#endif

#if BITS_PER_LONG == 32
void __cold btrfs_warn_32bit_limit(struct btrfs_fs_info *fs_info)
{
        if (!test_and_set_bit(BTRFS_FS_32BIT_WARN, &fs_info->flags)) {
                btrfs_warn(fs_info, "reaching 32bit limit for logical addresses");
                btrfs_warn(fs_info,
"due to page cache limit on 32bit systems, btrfs can't access metadata at or beyond %lluT",
                           BTRFS_32BIT_MAX_FILE_SIZE >> 40);
                btrfs_warn(fs_info,
                           "please consider upgrading to 64bit kernel/hardware");
        }
}

void __cold btrfs_err_32bit_limit(struct btrfs_fs_info *fs_info)
{
        if (!test_and_set_bit(BTRFS_FS_32BIT_ERROR, &fs_info->flags)) {
                btrfs_err(fs_info, "reached 32bit limit for logical addresses");
                btrfs_err(fs_info,
"due to page cache limit on 32bit systems, metadata beyond %lluT can't be accessed",
                          BTRFS_32BIT_MAX_FILE_SIZE >> 40);
                btrfs_err(fs_info,
                           "please consider upgrading to 64bit kernel/hardware");
        }
}
#endif

/*
 * We only mark the transaction aborted and then set the file system read-only.
 * This will prevent new transactions from starting or trying to join this
 * one.
 *
 * This means that error recovery at the call site is limited to freeing
 * any local memory allocations and passing the error code up without
 * further cleanup. The transaction should complete as it normally would
 * in the call path but will return -EIO.
 *
 * We'll complete the cleanup in btrfs_end_transaction and
 * btrfs_commit_transaction.
 */
__cold
void __btrfs_abort_transaction(struct btrfs_trans_handle *trans,
                               const char *function,
                               unsigned int line, int errno)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;

        WRITE_ONCE(trans->aborted, errno);
        WRITE_ONCE(trans->transaction->aborted, errno);
        /* Wake up anybody who may be waiting on this transaction */
        wake_up(&fs_info->transaction_wait);
        wake_up(&fs_info->transaction_blocked_wait);
        __btrfs_handle_fs_error(fs_info, function, line, errno, NULL);
}
/*
 * __btrfs_panic decodes unexpected, fatal errors from the caller,
 * issues an alert, and either panics or BUGs, depending on mount options.
 */
__cold
void __btrfs_panic(struct btrfs_fs_info *fs_info, const char *function,
                   unsigned int line, int errno, const char *fmt, ...)
{
        char *s_id = "<unknown>";
        const char *errstr;
        struct va_format vaf = { .fmt = fmt };
        va_list args;

        if (fs_info)
                s_id = fs_info->sb->s_id;

        va_start(args, fmt);
        vaf.va = &args;

        errstr = btrfs_decode_error(errno);
        if (fs_info && (btrfs_test_opt(fs_info, PANIC_ON_FATAL_ERROR)))
                panic(KERN_CRIT "BTRFS panic (device %s) in %s:%d: %pV (errno=%d %s)\n",
                        s_id, function, line, &vaf, errno, errstr);

        btrfs_crit(fs_info, "panic in %s:%d: %pV (errno=%d %s)",
                   function, line, &vaf, errno, errstr);
        va_end(args);
        /* Caller calls BUG() */
}

static void btrfs_put_super(struct super_block *sb)
{
        close_ctree(btrfs_sb(sb));
}

enum {
        Opt_acl, Opt_noacl,
        Opt_clear_cache,
        Opt_commit_interval,
        Opt_compress,
        Opt_compress_force,
        Opt_compress_force_type,
        Opt_compress_type,
        Opt_degraded,
        Opt_device,
        Opt_fatal_errors,
        Opt_flushoncommit, Opt_noflushoncommit,
        Opt_max_inline,
        Opt_barrier, Opt_nobarrier,
        Opt_datacow, Opt_nodatacow,
        Opt_datasum, Opt_nodatasum,
        Opt_defrag, Opt_nodefrag,
        Opt_discard, Opt_nodiscard,
        Opt_discard_mode,
        Opt_norecovery,
        Opt_ratio,
        Opt_rescan_uuid_tree,
        Opt_skip_balance,
        Opt_space_cache, Opt_no_space_cache,
        Opt_space_cache_version,
        Opt_ssd, Opt_nossd,
        Opt_ssd_spread, Opt_nossd_spread,
        Opt_subvol,
        Opt_subvol_empty,
        Opt_subvolid,
        Opt_thread_pool,
        Opt_treelog, Opt_notreelog,
        Opt_user_subvol_rm_allowed,

        /* Rescue options */
        Opt_rescue,
        Opt_usebackuproot,
        Opt_nologreplay,
        Opt_ignorebadroots,
        Opt_ignoredatacsums,
        Opt_rescue_all,

        /* Deprecated options */
        Opt_recovery,
        Opt_inode_cache, Opt_noinode_cache,

        /* Debugging options */
        Opt_check_integrity,
        Opt_check_integrity_including_extent_data,
        Opt_check_integrity_print_mask,
        Opt_enospc_debug, Opt_noenospc_debug,
#ifdef CONFIG_BTRFS_DEBUG
        Opt_fragment_data, Opt_fragment_metadata, Opt_fragment_all,
#endif
#ifdef CONFIG_BTRFS_FS_REF_VERIFY
        Opt_ref_verify,
#endif
        Opt_err,
};

static const match_table_t tokens = {
        {Opt_acl, "acl"},
        {Opt_noacl, "noacl"},
        {Opt_clear_cache, "clear_cache"},
        {Opt_commit_interval, "commit=%u"},
        {Opt_compress, "compress"},
        {Opt_compress_type, "compress=%s"},
        {Opt_compress_force, "compress-force"},
        {Opt_compress_force_type, "compress-force=%s"},
        {Opt_degraded, "degraded"},
        {Opt_device, "device=%s"},
        {Opt_fatal_errors, "fatal_errors=%s"},
        {Opt_flushoncommit, "flushoncommit"},
        {Opt_noflushoncommit, "noflushoncommit"},
        {Opt_inode_cache, "inode_cache"},
        {Opt_noinode_cache, "noinode_cache"},
        {Opt_max_inline, "max_inline=%s"},
        {Opt_barrier, "barrier"},
        {Opt_nobarrier, "nobarrier"},
        {Opt_datacow, "datacow"},
        {Opt_nodatacow, "nodatacow"},
        {Opt_datasum, "datasum"},
        {Opt_nodatasum, "nodatasum"},
        {Opt_defrag, "autodefrag"},
        {Opt_nodefrag, "noautodefrag"},
        {Opt_discard, "discard"},
        {Opt_discard_mode, "discard=%s"},
        {Opt_nodiscard, "nodiscard"},
        {Opt_norecovery, "norecovery"},
        {Opt_ratio, "metadata_ratio=%u"},
        {Opt_rescan_uuid_tree, "rescan_uuid_tree"},
        {Opt_skip_balance, "skip_balance"},
        {Opt_space_cache, "space_cache"},
        {Opt_no_space_cache, "nospace_cache"},
        {Opt_space_cache_version, "space_cache=%s"},
        {Opt_ssd, "ssd"},
        {Opt_nossd, "nossd"},
        {Opt_ssd_spread, "ssd_spread"},
        {Opt_nossd_spread, "nossd_spread"},
        {Opt_subvol, "subvol=%s"},
        {Opt_subvol_empty, "subvol="},
        {Opt_subvolid, "subvolid=%s"},
        {Opt_thread_pool, "thread_pool=%u"},
        {Opt_treelog, "treelog"},
        {Opt_notreelog, "notreelog"},
        {Opt_user_subvol_rm_allowed, "user_subvol_rm_allowed"},

        /* Rescue options */
        {Opt_rescue, "rescue=%s"},
        /* Deprecated, with alias rescue=nologreplay */
        {Opt_nologreplay, "nologreplay"},
        /* Deprecated, with alias rescue=usebackuproot */
        {Opt_usebackuproot, "usebackuproot"},

        /* Deprecated options */
        {Opt_recovery, "recovery"},

        /* Debugging options */
        {Opt_check_integrity, "check_int"},
        {Opt_check_integrity_including_extent_data, "check_int_data"},
        {Opt_check_integrity_print_mask, "check_int_print_mask=%u"},
        {Opt_enospc_debug, "enospc_debug"},
        {Opt_noenospc_debug, "noenospc_debug"},
#ifdef CONFIG_BTRFS_DEBUG
        {Opt_fragment_data, "fragment=data"},
        {Opt_fragment_metadata, "fragment=metadata"},
        {Opt_fragment_all, "fragment=all"},
#endif
#ifdef CONFIG_BTRFS_FS_REF_VERIFY
        {Opt_ref_verify, "ref_verify"},
#endif
        {Opt_err, NULL},
};

static const match_table_t rescue_tokens = {
        {Opt_usebackuproot, "usebackuproot"},
        {Opt_nologreplay, "nologreplay"},
        {Opt_ignorebadroots, "ignorebadroots"},
        {Opt_ignorebadroots, "ibadroots"},
        {Opt_ignoredatacsums, "ignoredatacsums"},
        {Opt_ignoredatacsums, "idatacsums"},
        {Opt_rescue_all, "all"},
        {Opt_err, NULL},
};

static bool check_ro_option(struct btrfs_fs_info *fs_info, unsigned long opt,
                            const char *opt_name)
{
        if (fs_info->mount_opt & opt) {
                btrfs_err(fs_info, "%s must be used with ro mount option",
                          opt_name);
                return true;
        }
        return false;
}

static int parse_rescue_options(struct btrfs_fs_info *info, const char *options)
{
        char *opts;
        char *orig;
        char *p;
        substring_t args[MAX_OPT_ARGS];
        int ret = 0;

        opts = kstrdup(options, GFP_KERNEL);
        if (!opts)
                return -ENOMEM;
        orig = opts;

        while ((p = strsep(&opts, ":")) != NULL) {
                int token;

                if (!*p)
                        continue;
                token = match_token(p, rescue_tokens, args);
                switch (token){
                case Opt_usebackuproot:
                        btrfs_info(info,
                                   "trying to use backup root at mount time");
                        btrfs_set_opt(info->mount_opt, USEBACKUPROOT);
                        break;
                case Opt_nologreplay:
                        btrfs_set_and_info(info, NOLOGREPLAY,
                                           "disabling log replay at mount time");
                        break;
                case Opt_ignorebadroots:
                        btrfs_set_and_info(info, IGNOREBADROOTS,
                                           "ignoring bad roots");
                        break;
                case Opt_ignoredatacsums:
                        btrfs_set_and_info(info, IGNOREDATACSUMS,
                                           "ignoring data csums");
                        break;
                case Opt_rescue_all:
                        btrfs_info(info, "enabling all of the rescue options");
                        btrfs_set_and_info(info, IGNOREDATACSUMS,
                                           "ignoring data csums");
                        btrfs_set_and_info(info, IGNOREBADROOTS,
                                           "ignoring bad roots");
                        btrfs_set_and_info(info, NOLOGREPLAY,
                                           "disabling log replay at mount time");
                        break;
                case Opt_err:
                        btrfs_info(info, "unrecognized rescue option '%s'", p);
                        ret = -EINVAL;
                        goto out;
                default:
                        break;
                }

        }
out:
        kfree(orig);
        return ret;
}

/*
 * Regular mount options parser.  Everything that is needed only when
 * reading in a new superblock is parsed here.
 * XXX JDM: This needs to be cleaned up for remount.
 */
int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
                        unsigned long new_flags)
{
        substring_t args[MAX_OPT_ARGS];
        char *p, *num;
        int intarg;
        int ret = 0;
        char *compress_type;
        bool compress_force = false;
        enum btrfs_compression_type saved_compress_type;
        int saved_compress_level;
        bool saved_compress_force;
        int no_compress = 0;

        if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
                btrfs_set_opt(info->mount_opt, FREE_SPACE_TREE);
        else if (btrfs_free_space_cache_v1_active(info)) {
                if (btrfs_is_zoned(info)) {
                        btrfs_info(info,
                        "zoned: clearing existing space cache");
                        btrfs_set_super_cache_generation(info->super_copy, 0);
                } else {
                        btrfs_set_opt(info->mount_opt, SPACE_CACHE);
                }
        }

        /*
         * Even the options are empty, we still need to do extra check
         * against new flags
         */
        if (!options)
                goto check;

        while ((p = strsep(&options, ",")) != NULL) {
                int token;
                if (!*p)
                        continue;

                token = match_token(p, tokens, args);
                switch (token) {
                case Opt_degraded:
                        btrfs_info(info, "allowing degraded mounts");
                        btrfs_set_opt(info->mount_opt, DEGRADED);
                        break;
                case Opt_subvol:
                case Opt_subvol_empty:
                case Opt_subvolid:
                case Opt_device:
                        /*
                         * These are parsed by btrfs_parse_subvol_options or
                         * btrfs_parse_device_options and can be ignored here.
                         */
                        break;
                case Opt_nodatasum:
                        btrfs_set_and_info(info, NODATASUM,
                                           "setting nodatasum");
                        break;
                case Opt_datasum:
                        if (btrfs_test_opt(info, NODATASUM)) {
                                if (btrfs_test_opt(info, NODATACOW))
                                        btrfs_info(info,
                                                   "setting datasum, datacow enabled");
                                else
                                        btrfs_info(info, "setting datasum");
                        }
                        btrfs_clear_opt(info->mount_opt, NODATACOW);
                        btrfs_clear_opt(info->mount_opt, NODATASUM);
                        break;
                case Opt_nodatacow:
                        if (!btrfs_test_opt(info, NODATACOW)) {
                                if (!btrfs_test_opt(info, COMPRESS) ||
                                    !btrfs_test_opt(info, FORCE_COMPRESS)) {
                                        btrfs_info(info,
                                                   "setting nodatacow, compression disabled");
                                } else {
                                        btrfs_info(info, "setting nodatacow");
                                }
                        }
                        btrfs_clear_opt(info->mount_opt, COMPRESS);
                        btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
                        btrfs_set_opt(info->mount_opt, NODATACOW);
                        btrfs_set_opt(info->mount_opt, NODATASUM);
                        break;
                case Opt_datacow:
                        btrfs_clear_and_info(info, NODATACOW,
                                             "setting datacow");
                        break;
                case Opt_compress_force:
                case Opt_compress_force_type:
                        compress_force = true;
                        fallthrough;
                case Opt_compress:
                case Opt_compress_type:
                        saved_compress_type = btrfs_test_opt(info,
                                                             COMPRESS) ?
                                info->compress_type : BTRFS_COMPRESS_NONE;
                        saved_compress_force =
                                btrfs_test_opt(info, FORCE_COMPRESS);
                        saved_compress_level = info->compress_level;
                        if (token == Opt_compress ||
                            token == Opt_compress_force ||
                            strncmp(args[0].from, "zlib", 4) == 0) {
                                compress_type = "zlib";

                                info->compress_type = BTRFS_COMPRESS_ZLIB;
                                info->compress_level = BTRFS_ZLIB_DEFAULT_LEVEL;
                                /*
                                 * args[0] contains uninitialized data since
                                 * for these tokens we don't expect any
                                 * parameter.
                                 */
                                if (token != Opt_compress &&
                                    token != Opt_compress_force)
                                        info->compress_level =
                                          btrfs_compress_str2level(
                                                        BTRFS_COMPRESS_ZLIB,
                                                        args[0].from + 4);
                                btrfs_set_opt(info->mount_opt, COMPRESS);
                                btrfs_clear_opt(info->mount_opt, NODATACOW);
                                btrfs_clear_opt(info->mount_opt, NODATASUM);
                                no_compress = 0;
                        } else if (strncmp(args[0].from, "lzo", 3) == 0) {
                                compress_type = "lzo";
                                info->compress_type = BTRFS_COMPRESS_LZO;
                                info->compress_level = 0;
                                btrfs_set_opt(info->mount_opt, COMPRESS);
                                btrfs_clear_opt(info->mount_opt, NODATACOW);
                                btrfs_clear_opt(info->mount_opt, NODATASUM);
                                btrfs_set_fs_incompat(info, COMPRESS_LZO);
                                no_compress = 0;
                        } else if (strncmp(args[0].from, "zstd", 4) == 0) {
                                compress_type = "zstd";
                                info->compress_type = BTRFS_COMPRESS_ZSTD;
                                info->compress_level =
                                        btrfs_compress_str2level(
                                                         BTRFS_COMPRESS_ZSTD,
                                                         args[0].from + 4);
                                btrfs_set_opt(info->mount_opt, COMPRESS);
                                btrfs_clear_opt(info->mount_opt, NODATACOW);
                                btrfs_clear_opt(info->mount_opt, NODATASUM);
                                btrfs_set_fs_incompat(info, COMPRESS_ZSTD);
                                no_compress = 0;
                        } else if (strncmp(args[0].from, "no", 2) == 0) {
                                compress_type = "no";
                                info->compress_level = 0;
                                info->compress_type = 0;
                                btrfs_clear_opt(info->mount_opt, COMPRESS);
                                btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
                                compress_force = false;
                                no_compress++;
                        } else {
                                ret = -EINVAL;
                                goto out;
                        }

                        if (compress_force) {
                                btrfs_set_opt(info->mount_opt, FORCE_COMPRESS);
                        } else {
                                /*
                                 * If we remount from compress-force=xxx to
                                 * compress=xxx, we need clear FORCE_COMPRESS
                                 * flag, otherwise, there is no way for users
                                 * to disable forcible compression separately.
                                 */
                                btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
                        }
                        if (no_compress == 1) {
                                btrfs_info(info, "use no compression");
                        } else if ((info->compress_type != saved_compress_type) ||
                                   (compress_force != saved_compress_force) ||
                                   (info->compress_level != saved_compress_level)) {
                                btrfs_info(info, "%s %s compression, level %d",
                                           (compress_force) ? "force" : "use",
                                           compress_type, info->compress_level);
                        }
                        compress_force = false;
                        break;
                case Opt_ssd:
                        btrfs_set_and_info(info, SSD,
                                           "enabling ssd optimizations");
                        btrfs_clear_opt(info->mount_opt, NOSSD);
                        break;
                case Opt_ssd_spread:
                        btrfs_set_and_info(info, SSD,
                                           "enabling ssd optimizations");
                        btrfs_set_and_info(info, SSD_SPREAD,
                                           "using spread ssd allocation scheme");
                        btrfs_clear_opt(info->mount_opt, NOSSD);
                        break;
                case Opt_nossd:
                        btrfs_set_opt(info->mount_opt, NOSSD);
                        btrfs_clear_and_info(info, SSD,
                                             "not using ssd optimizations");
                        fallthrough;
                case Opt_nossd_spread:
                        btrfs_clear_and_info(info, SSD_SPREAD,
                                             "not using spread ssd allocation scheme");
                        break;
                case Opt_barrier:
                        btrfs_clear_and_info(info, NOBARRIER,
                                             "turning on barriers");
                        break;
                case Opt_nobarrier:
                        btrfs_set_and_info(info, NOBARRIER,
                                           "turning off barriers");
                        break;
                case Opt_thread_pool:
                        ret = match_int(&args[0], &intarg);
                        if (ret) {
                                goto out;
                        } else if (intarg == 0) {
                                ret = -EINVAL;
                                goto out;
                        }
                        info->thread_pool_size = intarg;
                        break;
                case Opt_max_inline:
                        num = match_strdup(&args[0]);
                        if (num) {
                                info->max_inline = memparse(num, NULL);
                                kfree(num);

                                if (info->max_inline) {
                                        info->max_inline = min_t(u64,
                                                info->max_inline,
                                                info->sectorsize);
                                }
                                btrfs_info(info, "max_inline at %llu",
                                           info->max_inline);
                        } else {
                                ret = -ENOMEM;
                                goto out;
                        }
                        break;
                case Opt_acl:
#ifdef CONFIG_BTRFS_FS_POSIX_ACL
                        info->sb->s_flags |= SB_POSIXACL;
                        break;
#else
                        btrfs_err(info, "support for ACL not compiled in!");
                        ret = -EINVAL;
                        goto out;
#endif
                case Opt_noacl:
                        info->sb->s_flags &= ~SB_POSIXACL;
                        break;
                case Opt_notreelog:
                        btrfs_set_and_info(info, NOTREELOG,
                                           "disabling tree log");
                        break;
                case Opt_treelog:
                        btrfs_clear_and_info(info, NOTREELOG,
                                             "enabling tree log");
                        break;
                case Opt_norecovery:
                case Opt_nologreplay:
                        btrfs_warn(info,
                "'nologreplay' is deprecated, use 'rescue=nologreplay' instead");
                        btrfs_set_and_info(info, NOLOGREPLAY,
                                           "disabling log replay at mount time");
                        break;
                case Opt_flushoncommit:
                        btrfs_set_and_info(info, FLUSHONCOMMIT,
                                           "turning on flush-on-commit");
                        break;
                case Opt_noflushoncommit:
                        btrfs_clear_and_info(info, FLUSHONCOMMIT,
                                             "turning off flush-on-commit");
                        break;
                case Opt_ratio:
                        ret = match_int(&args[0], &intarg);
                        if (ret)
                                goto out;
                        info->metadata_ratio = intarg;
                        btrfs_info(info, "metadata ratio %u",
                                   info->metadata_ratio);
                        break;
                case Opt_discard:
                case Opt_discard_mode:
                        if (token == Opt_discard ||
                            strcmp(args[0].from, "sync") == 0) {
                                btrfs_clear_opt(info->mount_opt, DISCARD_ASYNC);
                                btrfs_set_and_info(info, DISCARD_SYNC,
                                                   "turning on sync discard");
                        } else if (strcmp(args[0].from, "async") == 0) {
                                btrfs_clear_opt(info->mount_opt, DISCARD_SYNC);
                                btrfs_set_and_info(info, DISCARD_ASYNC,
                                                   "turning on async discard");
                        } else {
                                ret = -EINVAL;
                                goto out;
                        }
                        break;
                case Opt_nodiscard:
                        btrfs_clear_and_info(info, DISCARD_SYNC,
                                             "turning off discard");
                        btrfs_clear_and_info(info, DISCARD_ASYNC,
                                             "turning off async discard");
                        break;
                case Opt_space_cache:
                case Opt_space_cache_version:
                        if (token == Opt_space_cache ||
                            strcmp(args[0].from, "v1") == 0) {
                                btrfs_clear_opt(info->mount_opt,
                                                FREE_SPACE_TREE);
                                btrfs_set_and_info(info, SPACE_CACHE,
                                           "enabling disk space caching");
                        } else if (strcmp(args[0].from, "v2") == 0) {
                                btrfs_clear_opt(info->mount_opt,
                                                SPACE_CACHE);
                                btrfs_set_and_info(info, FREE_SPACE_TREE,
                                                   "enabling free space tree");
                        } else {
                                ret = -EINVAL;
                                goto out;
                        }
                        break;
                case Opt_rescan_uuid_tree:
                        btrfs_set_opt(info->mount_opt, RESCAN_UUID_TREE);
                        break;
                case Opt_no_space_cache:
                        if (btrfs_test_opt(info, SPACE_CACHE)) {
                                btrfs_clear_and_info(info, SPACE_CACHE,
                                             "disabling disk space caching");
                        }
                        if (btrfs_test_opt(info, FREE_SPACE_TREE)) {
                                btrfs_clear_and_info(info, FREE_SPACE_TREE,
                                             "disabling free space tree");
                        }
                        break;
                case Opt_inode_cache:
                case Opt_noinode_cache:
                        btrfs_warn(info,
        "the 'inode_cache' option is deprecated and has no effect since 5.11");
                        break;
                case Opt_clear_cache:
                        btrfs_set_and_info(info, CLEAR_CACHE,
                                           "force clearing of disk cache");
                        break;
                case Opt_user_subvol_rm_allowed:
                        btrfs_set_opt(info->mount_opt, USER_SUBVOL_RM_ALLOWED);
                        break;
                case Opt_enospc_debug:
                        btrfs_set_opt(info->mount_opt, ENOSPC_DEBUG);
                        break;
                case Opt_noenospc_debug:
                        btrfs_clear_opt(info->mount_opt, ENOSPC_DEBUG);
                        break;
                case Opt_defrag:
                        btrfs_set_and_info(info, AUTO_DEFRAG,
                                           "enabling auto defrag");
                        break;
                case Opt_nodefrag:
                        btrfs_clear_and_info(info, AUTO_DEFRAG,
                                             "disabling auto defrag");
                        break;
                case Opt_recovery:
                case Opt_usebackuproot:
                        btrfs_warn(info,
                        "'%s' is deprecated, use 'rescue=usebackuproot' instead",
                                   token == Opt_recovery ? "recovery" :
                                   "usebackuproot");
                        btrfs_info(info,
                                   "trying to use backup root at mount time");
                        btrfs_set_opt(info->mount_opt, USEBACKUPROOT);
                        break;
                case Opt_skip_balance:
                        btrfs_set_opt(info->mount_opt, SKIP_BALANCE);
                        break;
#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
                case Opt_check_integrity_including_extent_data:
                        btrfs_info(info,
                                   "enabling check integrity including extent data");
                        btrfs_set_opt(info->mount_opt, CHECK_INTEGRITY_DATA);
                        btrfs_set_opt(info->mount_opt, CHECK_INTEGRITY);
                        break;
                case Opt_check_integrity:
                        btrfs_info(info, "enabling check integrity");
                        btrfs_set_opt(info->mount_opt, CHECK_INTEGRITY);
                        break;
                case Opt_check_integrity_print_mask:
                        ret = match_int(&args[0], &intarg);
                        if (ret)
                                goto out;
                        info->check_integrity_print_mask = intarg;
                        btrfs_info(info, "check_integrity_print_mask 0x%x",
                                   info->check_integrity_print_mask);
                        break;
#else
                case Opt_check_integrity_including_extent_data:
                case Opt_check_integrity:
                case Opt_check_integrity_print_mask:
                        btrfs_err(info,
                                  "support for check_integrity* not compiled in!");
                        ret = -EINVAL;
                        goto out;
#endif
                case Opt_fatal_errors:
                        if (strcmp(args[0].from, "panic") == 0)
                                btrfs_set_opt(info->mount_opt,
                                              PANIC_ON_FATAL_ERROR);
                        else if (strcmp(args[0].from, "bug") == 0)
                                btrfs_clear_opt(info->mount_opt,
                                              PANIC_ON_FATAL_ERROR);
                        else {
                                ret = -EINVAL;
                                goto out;
                        }
                        break;
                case Opt_commit_interval:
                        intarg = 0;
                        ret = match_int(&args[0], &intarg);
                        if (ret)
                                goto out;
                        if (intarg == 0) {
                                btrfs_info(info,
                                           "using default commit interval %us",
                                           BTRFS_DEFAULT_COMMIT_INTERVAL);
                                intarg = BTRFS_DEFAULT_COMMIT_INTERVAL;
                        } else if (intarg > 300) {
                                btrfs_warn(info, "excessive commit interval %d",
                                           intarg);
                        }
                        info->commit_interval = intarg;
                        break;
                case Opt_rescue:
                        ret = parse_rescue_options(info, args[0].from);
                        if (ret < 0)
                                goto out;
                        break;
#ifdef CONFIG_BTRFS_DEBUG
                case Opt_fragment_all:
                        btrfs_info(info, "fragmenting all space");
                        btrfs_set_opt(info->mount_opt, FRAGMENT_DATA);
                        btrfs_set_opt(info->mount_opt, FRAGMENT_METADATA);
                        break;
                case Opt_fragment_metadata:

                        btrfs_info(info, "fragmenting metadata");
                        btrfs_set_opt(info->mount_opt,
                                      FRAGMENT_METADATA);
                        break;
                case Opt_fragment_data:
                        btrfs_info(info, "fragmenting data");
                        btrfs_set_opt(info->mount_opt, FRAGMENT_DATA);
                        break;
#endif
#ifdef CONFIG_BTRFS_FS_REF_VERIFY
                case Opt_ref_verify:
                        btrfs_info(info, "doing ref verification");
                        btrfs_set_opt(info->mount_opt, REF_VERIFY);
                        break;
#endif
                case Opt_err:
                        btrfs_err(info, "unrecognized mount option '%s'", p);
                        ret = -EINVAL;
                        goto out;
                default:
                        break;
                }
        }
check:
        /* We're read-only, don't have to check. */
        if (new_flags & SB_RDONLY)
                goto out;

        if (check_ro_option(info, BTRFS_MOUNT_NOLOGREPLAY, "nologreplay") ||
            check_ro_option(info, BTRFS_MOUNT_IGNOREBADROOTS, "ignorebadroots") ||
            check_ro_option(info, BTRFS_MOUNT_IGNOREDATACSUMS, "ignoredatacsums"))
                ret = -EINVAL;
out:
        if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE) &&
            !btrfs_test_opt(info, FREE_SPACE_TREE) &&
            !btrfs_test_opt(info, CLEAR_CACHE)) {
                btrfs_err(info, "cannot disable free space tree");
                ret = -EINVAL;

        }
        if (!ret)
                ret = btrfs_check_mountopts_zoned(info);
        if (!ret && btrfs_test_opt(info, SPACE_CACHE))
                btrfs_info(info, "disk space caching is enabled");
        if (!ret && btrfs_test_opt(info, FREE_SPACE_TREE))
                btrfs_info(info, "using free space tree");
        return ret;
}

/*
 * Parse mount options that are required early in the mount process.
 *
 * All other options will be parsed on much later in the mount process and
 * only when we need to allocate a new super block.
 */
static int btrfs_parse_device_options(const char *options, fmode_t flags,
                                      void *holder)
{
        substring_t args[MAX_OPT_ARGS];
        char *device_name, *opts, *orig, *p;
        struct btrfs_device *device = NULL;
        int error = 0;

        lockdep_assert_held(&uuid_mutex);

        if (!options)
                return 0;

        /*
         * strsep changes the string, duplicate it because btrfs_parse_options
         * gets called later
         */
        opts = kstrdup(options, GFP_KERNEL);
        if (!opts)
                return -ENOMEM;
        orig = opts;

        while ((p = strsep(&opts, ",")) != NULL) {
                int token;

                if (!*p)
                        continue;

                token = match_token(p, tokens, args);
                if (token == Opt_device) {
                        device_name = match_strdup(&args[0]);
                        if (!device_name) {
                                error = -ENOMEM;
                                goto out;
                        }
                        device = btrfs_scan_one_device(device_name, flags,
                                        holder);
                        kfree(device_name);
                        if (IS_ERR(device)) {
                                error = PTR_ERR(device);
                                goto out;
                        }
                }
        }

out:
        kfree(orig);
        return error;
}

/*
 * Parse mount options that are related to subvolume id
 *
 * The value is later passed to mount_subvol()
 */
static int btrfs_parse_subvol_options(const char *options, char **subvol_name,
                u64 *subvol_objectid)
{
        substring_t args[MAX_OPT_ARGS];
        char *opts, *orig, *p;
        int error = 0;
        u64 subvolid;

        if (!options)
                return 0;

        /*
         * strsep changes the string, duplicate it because
         * btrfs_parse_device_options gets called later
         */
        opts = kstrdup(options, GFP_KERNEL);
        if (!opts)
                return -ENOMEM;
        orig = opts;

        while ((p = strsep(&opts, ",")) != NULL) {
                int token;
                if (!*p)
                        continue;

                token = match_token(p, tokens, args);
                switch (token) {
                case Opt_subvol:
                        kfree(*subvol_name);
                        *subvol_name = match_strdup(&args[0]);
                        if (!*subvol_name) {
                                error = -ENOMEM;
                                goto out;
                        }
                        break;
                case Opt_subvolid:
                        error = match_u64(&args[0], &subvolid);
                        if (error)
                                goto out;

                        /* we want the original fs_tree */
                        if (subvolid == 0)
                                subvolid = BTRFS_FS_TREE_OBJECTID;

                        *subvol_objectid = subvolid;
                        break;
                default:
                        break;
                }
        }

out:
        kfree(orig);
        return error;
}

char *btrfs_get_subvol_name_from_objectid(struct btrfs_fs_info *fs_info,
                                          u64 subvol_objectid)
{
        struct btrfs_root *root = fs_info->tree_root;
        struct btrfs_root *fs_root = NULL;
        struct btrfs_root_ref *root_ref;
        struct btrfs_inode_ref *inode_ref;
        struct btrfs_key key;
        struct btrfs_path *path = NULL;
        char *name = NULL, *ptr;
        u64 dirid;
        int len;
        int ret;

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                goto err;
        }

        name = kmalloc(PATH_MAX, GFP_KERNEL);
        if (!name) {
                ret = -ENOMEM;
                goto err;
        }
        ptr = name + PATH_MAX - 1;
        ptr[0] = '\0';

        /*
         * Walk up the subvolume trees in the tree of tree roots by root
         * backrefs until we hit the top-level subvolume.
         */
        while (subvol_objectid != BTRFS_FS_TREE_OBJECTID) {
                key.objectid = subvol_objectid;
                key.type = BTRFS_ROOT_BACKREF_KEY;
                key.offset = (u64)-1;

                ret = btrfs_search_backwards(root, &key, path);
                if (ret < 0) {
                        goto err;
                } else if (ret > 0) {
                        ret = -ENOENT;
                        goto err;
                }

                subvol_objectid = key.offset;

                root_ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                          struct btrfs_root_ref);
                len = btrfs_root_ref_name_len(path->nodes[0], root_ref);
                ptr -= len + 1;
                if (ptr < name) {
                        ret = -ENAMETOOLONG;
                        goto err;
                }
                read_extent_buffer(path->nodes[0], ptr + 1,
                                   (unsigned long)(root_ref + 1), len);
                ptr[0] = '/';
                dirid = btrfs_root_ref_dirid(path->nodes[0], root_ref);
                btrfs_release_path(path);

                fs_root = btrfs_get_fs_root(fs_info, subvol_objectid, true);
                if (IS_ERR(fs_root)) {
                        ret = PTR_ERR(fs_root);
                        fs_root = NULL;
                        goto err;
                }

                /*
                 * Walk up the filesystem tree by inode refs until we hit the
                 * root directory.
                 */
                while (dirid != BTRFS_FIRST_FREE_OBJECTID) {
                        key.objectid = dirid;
                        key.type = BTRFS_INODE_REF_KEY;
                        key.offset = (u64)-1;

                        ret = btrfs_search_backwards(fs_root, &key, path);
                        if (ret < 0) {
                                goto err;
                        } else if (ret > 0) {
                                ret = -ENOENT;
                                goto err;
                        }

                        dirid = key.offset;

                        inode_ref = btrfs_item_ptr(path->nodes[0],
                                                   path->slots[0],
                                                   struct btrfs_inode_ref);
                        len = btrfs_inode_ref_name_len(path->nodes[0],
                                                       inode_ref);
                        ptr -= len + 1;
                        if (ptr < name) {
                                ret = -ENAMETOOLONG;
                                goto err;
                        }
                        read_extent_buffer(path->nodes[0], ptr + 1,
                                           (unsigned long)(inode_ref + 1), len);
                        ptr[0] = '/';
                        btrfs_release_path(path);
                }
                btrfs_put_root(fs_root);
                fs_root = NULL;
        }

        btrfs_free_path(path);
        if (ptr == name + PATH_MAX - 1) {
                name[0] = '/';
                name[1] = '\0';
        } else {
                memmove(name, ptr, name + PATH_MAX - ptr);
        }
        return name;

err:
        btrfs_put_root(fs_root);
        btrfs_free_path(path);
        kfree(name);
        return ERR_PTR(ret);
}

static int get_default_subvol_objectid(struct btrfs_fs_info *fs_info, u64 *objectid)
{
        struct btrfs_root *root = fs_info->tree_root;
        struct btrfs_dir_item *di;
        struct btrfs_path *path;
        struct btrfs_key location;
        u64 dir_id;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        /*
         * Find the "default" dir item which points to the root item that we
         * will mount by default if we haven't been given a specific subvolume
         * to mount.
         */
        dir_id = btrfs_super_root_dir(fs_info->super_copy);
        di = btrfs_lookup_dir_item(NULL, root, path, dir_id, "default", 7, 0);
        if (IS_ERR(di)) {
                btrfs_free_path(path);
                return PTR_ERR(di);
        }
        if (!di) {
                /*
                 * Ok the default dir item isn't there.  This is weird since
                 * it's always been there, but don't freak out, just try and
                 * mount the top-level subvolume.
                 */
                btrfs_free_path(path);
                *objectid = BTRFS_FS_TREE_OBJECTID;
                return 0;
        }

        btrfs_dir_item_key_to_cpu(path->nodes[0], di, &location);
        btrfs_free_path(path);
        *objectid = location.objectid;
        return 0;
}

static int btrfs_fill_super(struct super_block *sb,
                            struct btrfs_fs_devices *fs_devices,
                            void *data)
{
        struct inode *inode;
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        int err;

        sb->s_maxbytes = MAX_LFS_FILESIZE;
        sb->s_magic = BTRFS_SUPER_MAGIC;
        sb->s_op = &btrfs_super_ops;
        sb->s_d_op = &btrfs_dentry_operations;
        sb->s_export_op = &btrfs_export_ops;
#ifdef CONFIG_FS_VERITY
        sb->s_vop = &btrfs_verityops;
#endif
        sb->s_xattr = btrfs_xattr_handlers;
        sb->s_time_gran = 1;
#ifdef CONFIG_BTRFS_FS_POSIX_ACL
        sb->s_flags |= SB_POSIXACL;
#endif
        sb->s_flags |= SB_I_VERSION;
        sb->s_iflags |= SB_I_CGROUPWB;

        err = super_setup_bdi(sb);
        if (err) {
                btrfs_err(fs_info, "super_setup_bdi failed");
                return err;
        }

        err = open_ctree(sb, fs_devices, (char *)data);
        if (err) {
                btrfs_err(fs_info, "open_ctree failed");
                return err;
        }

        inode = btrfs_iget(sb, BTRFS_FIRST_FREE_OBJECTID, fs_info->fs_root);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                goto fail_close;
        }

        sb->s_root = d_make_root(inode);
        if (!sb->s_root) {
                err = -ENOMEM;
                goto fail_close;
        }

        cleancache_init_fs(sb);
        sb->s_flags |= SB_ACTIVE;
        return 0;

fail_close:
        close_ctree(fs_info);
        return err;
}

int btrfs_sync_fs(struct super_block *sb, int wait)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        struct btrfs_root *root = fs_info->tree_root;

        trace_btrfs_sync_fs(fs_info, wait);

        if (!wait) {
                filemap_flush(fs_info->btree_inode->i_mapping);
                return 0;
        }

        btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);

        trans = btrfs_attach_transaction_barrier(root);
        if (IS_ERR(trans)) {
                /* no transaction, don't bother */
                if (PTR_ERR(trans) == -ENOENT) {
                        /*
                         * Exit unless we have some pending changes
                         * that need to go through commit
                         */
                        if (fs_info->pending_changes == 0)
                                return 0;
                        /*
                         * A non-blocking test if the fs is frozen. We must not
                         * start a new transaction here otherwise a deadlock
                         * happens. The pending operations are delayed to the
                         * next commit after thawing.
                         */
                        if (sb_start_write_trylock(sb))
                                sb_end_write(sb);
                        else
                                return 0;
                        trans = btrfs_start_transaction(root, 0);
                }
                if (IS_ERR(trans))
                        return PTR_ERR(trans);
        }
        return btrfs_commit_transaction(trans);
}

static void print_rescue_option(struct seq_file *seq, const char *s, bool *printed)
{
        seq_printf(seq, "%s%s", (*printed) ? ":" : ",rescue=", s);
        *printed = true;
}

static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
{
        struct btrfs_fs_info *info = btrfs_sb(dentry->d_sb);
        const char *compress_type;
        const char *subvol_name;
        bool printed = false;

        if (btrfs_test_opt(info, DEGRADED))
                seq_puts(seq, ",degraded");
        if (btrfs_test_opt(info, NODATASUM))
                seq_puts(seq, ",nodatasum");
        if (btrfs_test_opt(info, NODATACOW))
                seq_puts(seq, ",nodatacow");
        if (btrfs_test_opt(info, NOBARRIER))
                seq_puts(seq, ",nobarrier");
        if (info->max_inline != BTRFS_DEFAULT_MAX_INLINE)
                seq_printf(seq, ",max_inline=%llu", info->max_inline);
        if (info->thread_pool_size !=  min_t(unsigned long,
                                             num_online_cpus() + 2, 8))
                seq_printf(seq, ",thread_pool=%u", info->thread_pool_size);
        if (btrfs_test_opt(info, COMPRESS)) {
                compress_type = btrfs_compress_type2str(info->compress_type);
                if (btrfs_test_opt(info, FORCE_COMPRESS))
                        seq_printf(seq, ",compress-force=%s", compress_type);
                else
                        seq_printf(seq, ",compress=%s", compress_type);
                if (info->compress_level)
                        seq_printf(seq, ":%d", info->compress_level);
        }
        if (btrfs_test_opt(info, NOSSD))
                seq_puts(seq, ",nossd");
        if (btrfs_test_opt(info, SSD_SPREAD))
                seq_puts(seq, ",ssd_spread");
        else if (btrfs_test_opt(info, SSD))
                seq_puts(seq, ",ssd");
        if (btrfs_test_opt(info, NOTREELOG))
                seq_puts(seq, ",notreelog");
        if (btrfs_test_opt(info, NOLOGREPLAY))
                print_rescue_option(seq, "nologreplay", &printed);
        if (btrfs_test_opt(info, USEBACKUPROOT))
                print_rescue_option(seq, "usebackuproot", &printed);
        if (btrfs_test_opt(info, IGNOREBADROOTS))
                print_rescue_option(seq, "ignorebadroots", &printed);
        if (btrfs_test_opt(info, IGNOREDATACSUMS))
                print_rescue_option(seq, "ignoredatacsums", &printed);
        if (btrfs_test_opt(info, FLUSHONCOMMIT))
                seq_puts(seq, ",flushoncommit");
        if (btrfs_test_opt(info, DISCARD_SYNC))
                seq_puts(seq, ",discard");
        if (btrfs_test_opt(info, DISCARD_ASYNC))
                seq_puts(seq, ",discard=async");
        if (!(info->sb->s_flags & SB_POSIXACL))
                seq_puts(seq, ",noacl");
        if (btrfs_free_space_cache_v1_active(info))
                seq_puts(seq, ",space_cache");
        else if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
                seq_puts(seq, ",space_cache=v2");
        else
                seq_puts(seq, ",nospace_cache");
        if (btrfs_test_opt(info, RESCAN_UUID_TREE))
                seq_puts(seq, ",rescan_uuid_tree");
        if (btrfs_test_opt(info, CLEAR_CACHE))
                seq_puts(seq, ",clear_cache");
        if (btrfs_test_opt(info, USER_SUBVOL_RM_ALLOWED))
                seq_puts(seq, ",user_subvol_rm_allowed");
        if (btrfs_test_opt(info, ENOSPC_DEBUG))
                seq_puts(seq, ",enospc_debug");
        if (btrfs_test_opt(info, AUTO_DEFRAG))
                seq_puts(seq, ",autodefrag");
        if (btrfs_test_opt(info, SKIP_BALANCE))
                seq_puts(seq, ",skip_balance");
#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
        if (btrfs_test_opt(info, CHECK_INTEGRITY_DATA))
                seq_puts(seq, ",check_int_data");
        else if (btrfs_test_opt(info, CHECK_INTEGRITY))
                seq_puts(seq, ",check_int");
        if (info->check_integrity_print_mask)
                seq_printf(seq, ",check_int_print_mask=%d",
                                info->check_integrity_print_mask);
#endif
        if (info->metadata_ratio)
                seq_printf(seq, ",metadata_ratio=%u", info->metadata_ratio);
        if (btrfs_test_opt(info, PANIC_ON_FATAL_ERROR))
                seq_puts(seq, ",fatal_errors=panic");
        if (info->commit_interval != BTRFS_DEFAULT_COMMIT_INTERVAL)
                seq_printf(seq, ",commit=%u", info->commit_interval);
#ifdef CONFIG_BTRFS_DEBUG
        if (btrfs_test_opt(info, FRAGMENT_DATA))
                seq_puts(seq, ",fragment=data");
        if (btrfs_test_opt(info, FRAGMENT_METADATA))
                seq_puts(seq, ",fragment=metadata");
#endif
        if (btrfs_test_opt(info, REF_VERIFY))
                seq_puts(seq, ",ref_verify");
        seq_printf(seq, ",subvolid=%llu",
                  BTRFS_I(d_inode(dentry))->root->root_key.objectid);
        subvol_name = btrfs_get_subvol_name_from_objectid(info,
                        BTRFS_I(d_inode(dentry))->root->root_key.objectid);
        if (!IS_ERR(subvol_name)) {
                seq_puts(seq, ",subvol=");
                seq_escape(seq, subvol_name, " \t\n\\");
                kfree(subvol_name);
        }
        return 0;
}

static int btrfs_test_super(struct super_block *s, void *data)
{
        struct btrfs_fs_info *p = data;
        struct btrfs_fs_info *fs_info = btrfs_sb(s);

        return fs_info->fs_devices == p->fs_devices;
}

static int btrfs_set_super(struct super_block *s, void *data)
{
        int err = set_anon_super(s, data);
        if (!err)
                s->s_fs_info = data;
        return err;
}

/*
 * subvolumes are identified by ino 256
 */
static inline int is_subvolume_inode(struct inode *inode)
{
        if (inode && inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
                return 1;
        return 0;
}

static struct dentry *mount_subvol(const char *subvol_name, u64 subvol_objectid,
                                   struct vfsmount *mnt)
{
        struct dentry *root;
        int ret;

        if (!subvol_name) {
                if (!subvol_objectid) {
                        ret = get_default_subvol_objectid(btrfs_sb(mnt->mnt_sb),
                                                          &subvol_objectid);
                        if (ret) {
                                root = ERR_PTR(ret);
                                goto out;
                        }
                }
                subvol_name = btrfs_get_subvol_name_from_objectid(
                                        btrfs_sb(mnt->mnt_sb), subvol_objectid);
                if (IS_ERR(subvol_name)) {
                        root = ERR_CAST(subvol_name);
                        subvol_name = NULL;
                        goto out;
                }

        }

        root = mount_subtree(mnt, subvol_name);
        /* mount_subtree() drops our reference on the vfsmount. */
        mnt = NULL;

        if (!IS_ERR(root)) {
                struct super_block *s = root->d_sb;
                struct btrfs_fs_info *fs_info = btrfs_sb(s);
                struct inode *root_inode = d_inode(root);
                u64 root_objectid = BTRFS_I(root_inode)->root->root_key.objectid;

                ret = 0;
                if (!is_subvolume_inode(root_inode)) {
                        btrfs_err(fs_info, "'%s' is not a valid subvolume",
                               subvol_name);
                        ret = -EINVAL;
                }
                if (subvol_objectid && root_objectid != subvol_objectid) {
                        /*
                         * This will also catch a race condition where a
                         * subvolume which was passed by ID is renamed and
                         * another subvolume is renamed over the old location.
                         */
                        btrfs_err(fs_info,
                                  "subvol '%s' does not match subvolid %llu",
                                  subvol_name, subvol_objectid);
                        ret = -EINVAL;
                }
                if (ret) {
                        dput(root);
                        root = ERR_PTR(ret);
                        deactivate_locked_super(s);
                }
        }

out:
        mntput(mnt);
        kfree(subvol_name);
        return root;
}

/*
 * Find a superblock for the given device / mount point.
 *
 * Note: This is based on mount_bdev from fs/super.c with a few additions
 *       for multiple device setup.  Make sure to keep it in sync.
 */
static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
                int flags, const char *device_name, void *data)
{
        struct block_device *bdev = NULL;
        struct super_block *s;
        struct btrfs_device *device = NULL;
        struct btrfs_fs_devices *fs_devices = NULL;
        struct btrfs_fs_info *fs_info = NULL;
        void *new_sec_opts = NULL;
        fmode_t mode = FMODE_READ;
        int error = 0;

        if (!(flags & SB_RDONLY))
                mode |= FMODE_WRITE;

        if (data) {
                error = security_sb_eat_lsm_opts(data, &new_sec_opts);
                if (error)
                        return ERR_PTR(error);
        }

        /*
         * Setup a dummy root and fs_info for test/set super.  This is because
         * we don't actually fill this stuff out until open_ctree, but we need
         * then open_ctree will properly initialize the file system specific
         * settings later.  btrfs_init_fs_info initializes the static elements
         * of the fs_info (locks and such) to make cleanup easier if we find a
         * superblock with our given fs_devices later on at sget() time.
         */
        fs_info = kvzalloc(sizeof(struct btrfs_fs_info), GFP_KERNEL);
        if (!fs_info) {
                error = -ENOMEM;
                goto error_sec_opts;
        }
        btrfs_init_fs_info(fs_info);

        fs_info->super_copy = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_KERNEL);
        fs_info->super_for_commit = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_KERNEL);
        if (!fs_info->super_copy || !fs_info->super_for_commit) {
                error = -ENOMEM;
                goto error_fs_info;
        }

        mutex_lock(&uuid_mutex);
        error = btrfs_parse_device_options(data, mode, fs_type);
        if (error) {
                mutex_unlock(&uuid_mutex);
                goto error_fs_info;
        }

        device = btrfs_scan_one_device(device_name, mode, fs_type);
        if (IS_ERR(device)) {
                mutex_unlock(&uuid_mutex);
                error = PTR_ERR(device);
                goto error_fs_info;
        }

        fs_devices = device->fs_devices;
        fs_info->fs_devices = fs_devices;

        error = btrfs_open_devices(fs_devices, mode, fs_type);
        mutex_unlock(&uuid_mutex);
        if (error)
                goto error_fs_info;

        if (!(flags & SB_RDONLY) && fs_devices->rw_devices == 0) {
                error = -EACCES;
                goto error_close_devices;
        }

        bdev = fs_devices->latest_bdev;
        s = sget(fs_type, btrfs_test_super, btrfs_set_super, flags | SB_NOSEC,
                 fs_info);
        if (IS_ERR(s)) {
                error = PTR_ERR(s);
                goto error_close_devices;
        }

        if (s->s_root) {
                btrfs_close_devices(fs_devices);
                btrfs_free_fs_info(fs_info);
                if ((flags ^ s->s_flags) & SB_RDONLY)
                        error = -EBUSY;
        } else {
                snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
                btrfs_sb(s)->bdev_holder = fs_type;
                if (!strstr(crc32c_impl(), "generic"))
                        set_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags);
                error = btrfs_fill_super(s, fs_devices, data);
        }
        if (!error)
                error = security_sb_set_mnt_opts(s, new_sec_opts, 0, NULL);
        security_free_mnt_opts(&new_sec_opts);
        if (error) {
                deactivate_locked_super(s);
                return ERR_PTR(error);
        }

        return dget(s->s_root);

error_close_devices:
        btrfs_close_devices(fs_devices);
error_fs_info:
        btrfs_free_fs_info(fs_info);
error_sec_opts:
        security_free_mnt_opts(&new_sec_opts);
        return ERR_PTR(error);
}

/*
 * Mount function which is called by VFS layer.
 *
 * In order to allow mounting a subvolume directly, btrfs uses mount_subtree()
 * which needs vfsmount* of device's root (/).  This means device's root has to
 * be mounted internally in any case.
 *
 * Operation flow:
 *   1. Parse subvol id related options for later use in mount_subvol().
 *
 *   2. Mount device's root (/) by calling vfs_kern_mount().
 *
 *      NOTE: vfs_kern_mount() is used by VFS to call btrfs_mount() in the
 *      first place. In order to avoid calling btrfs_mount() again, we use
 *      different file_system_type which is not registered to VFS by
 *      register_filesystem() (btrfs_root_fs_type). As a result,
 *      btrfs_mount_root() is called. The return value will be used by
 *      mount_subtree() in mount_subvol().
 *
 *   3. Call mount_subvol() to get the dentry of subvolume. Since there is
 *      "btrfs subvolume set-default", mount_subvol() is called always.
 */
static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
                const char *device_name, void *data)
{
        struct vfsmount *mnt_root;
        struct dentry *root;
        char *subvol_name = NULL;
        u64 subvol_objectid = 0;
        int error = 0;

        error = btrfs_parse_subvol_options(data, &subvol_name,
                                        &subvol_objectid);
        if (error) {
                kfree(subvol_name);
                return ERR_PTR(error);
        }

        /* mount device's root (/) */
        mnt_root = vfs_kern_mount(&btrfs_root_fs_type, flags, device_name, data);
        if (PTR_ERR_OR_ZERO(mnt_root) == -EBUSY) {
                if (flags & SB_RDONLY) {
                        mnt_root = vfs_kern_mount(&btrfs_root_fs_type,
                                flags & ~SB_RDONLY, device_name, data);
                } else {
                        mnt_root = vfs_kern_mount(&btrfs_root_fs_type,
                                flags | SB_RDONLY, device_name, data);
                        if (IS_ERR(mnt_root)) {
                                root = ERR_CAST(mnt_root);
                                kfree(subvol_name);
                                goto out;
                        }

                        down_write(&mnt_root->mnt_sb->s_umount);
                        error = btrfs_remount(mnt_root->mnt_sb, &flags, NULL);
                        up_write(&mnt_root->mnt_sb->s_umount);
                        if (error < 0) {
                                root = ERR_PTR(error);
                                mntput(mnt_root);
                                kfree(subvol_name);
                                goto out;
                        }
                }
        }
        if (IS_ERR(mnt_root)) {
                root = ERR_CAST(mnt_root);
                kfree(subvol_name);
                goto out;
        }

        /* mount_subvol() will free subvol_name and mnt_root */
        root = mount_subvol(subvol_name, subvol_objectid, mnt_root);

out:
        return root;
}

static void btrfs_resize_thread_pool(struct btrfs_fs_info *fs_info,
                                     u32 new_pool_size, u32 old_pool_size)
{
        if (new_pool_size == old_pool_size)
                return;

        fs_info->thread_pool_size = new_pool_size;

        btrfs_info(fs_info, "resize thread pool %d -> %d",
               old_pool_size, new_pool_size);

        btrfs_workqueue_set_max(fs_info->workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->delalloc_workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->caching_workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->endio_workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->endio_meta_workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->endio_meta_write_workers,
                                new_pool_size);
        btrfs_workqueue_set_max(fs_info->endio_write_workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->endio_freespace_worker, new_pool_size);
        btrfs_workqueue_set_max(fs_info->delayed_workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->readahead_workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->scrub_wr_completion_workers,
                                new_pool_size);
}

static inline void btrfs_remount_begin(struct btrfs_fs_info *fs_info,
                                       unsigned long old_opts, int flags)
{
        if (btrfs_raw_test_opt(old_opts, AUTO_DEFRAG) &&
            (!btrfs_raw_test_opt(fs_info->mount_opt, AUTO_DEFRAG) ||
             (flags & SB_RDONLY))) {
                /* wait for any defraggers to finish */
                wait_event(fs_info->transaction_wait,
                           (atomic_read(&fs_info->defrag_running) == 0));
                if (flags & SB_RDONLY)
                        sync_filesystem(fs_info->sb);
        }
}

static inline void btrfs_remount_cleanup(struct btrfs_fs_info *fs_info,
                                         unsigned long old_opts)
{
        const bool cache_opt = btrfs_test_opt(fs_info, SPACE_CACHE);

        /*
         * We need to cleanup all defragable inodes if the autodefragment is
         * close or the filesystem is read only.
         */
        if (btrfs_raw_test_opt(old_opts, AUTO_DEFRAG) &&
            (!btrfs_raw_test_opt(fs_info->mount_opt, AUTO_DEFRAG) || sb_rdonly(fs_info->sb))) {
                btrfs_cleanup_defrag_inodes(fs_info);
        }

        /* If we toggled discard async */
        if (!btrfs_raw_test_opt(old_opts, DISCARD_ASYNC) &&
            btrfs_test_opt(fs_info, DISCARD_ASYNC))
                btrfs_discard_resume(fs_info);
        else if (btrfs_raw_test_opt(old_opts, DISCARD_ASYNC) &&
                 !btrfs_test_opt(fs_info, DISCARD_ASYNC))
                btrfs_discard_cleanup(fs_info);

        /* If we toggled space cache */
        if (cache_opt != btrfs_free_space_cache_v1_active(fs_info))
                btrfs_set_free_space_cache_v1_active(fs_info, cache_opt);
}

static int btrfs_remount(struct super_block *sb, int *flags, char *data)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        unsigned old_flags = sb->s_flags;
        unsigned long old_opts = fs_info->mount_opt;
        unsigned long old_compress_type = fs_info->compress_type;
        u64 old_max_inline = fs_info->max_inline;
        u32 old_thread_pool_size = fs_info->thread_pool_size;
        u32 old_metadata_ratio = fs_info->metadata_ratio;
        int ret;

        sync_filesystem(sb);
        set_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);

        if (data) {
                void *new_sec_opts = NULL;

                ret = security_sb_eat_lsm_opts(data, &new_sec_opts);
                if (!ret)
                        ret = security_sb_remount(sb, new_sec_opts);
                security_free_mnt_opts(&new_sec_opts);
                if (ret)
                        goto restore;
        }

        ret = btrfs_parse_options(fs_info, data, *flags);
        if (ret)
                goto restore;

        btrfs_remount_begin(fs_info, old_opts, *flags);
        btrfs_resize_thread_pool(fs_info,
                fs_info->thread_pool_size, old_thread_pool_size);

        if ((bool)btrfs_test_opt(fs_info, FREE_SPACE_TREE) !=
            (bool)btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE) &&
            (!sb_rdonly(sb) || (*flags & SB_RDONLY))) {
                btrfs_warn(fs_info,
                "remount supports changing free space tree only from ro to rw");
                /* Make sure free space cache options match the state on disk */
                if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
                        btrfs_set_opt(fs_info->mount_opt, FREE_SPACE_TREE);
                        btrfs_clear_opt(fs_info->mount_opt, SPACE_CACHE);
                }
                if (btrfs_free_space_cache_v1_active(fs_info)) {
                        btrfs_clear_opt(fs_info->mount_opt, FREE_SPACE_TREE);
                        btrfs_set_opt(fs_info->mount_opt, SPACE_CACHE);
                }
        }

        if ((bool)(*flags & SB_RDONLY) == sb_rdonly(sb))
                goto out;

        if (*flags & SB_RDONLY) {
                /*
                 * this also happens on 'umount -rf' or on shutdown, when
                 * the filesystem is busy.
                 */
                cancel_work_sync(&fs_info->async_reclaim_work);
                cancel_work_sync(&fs_info->async_data_reclaim_work);

                btrfs_discard_cleanup(fs_info);

                /* wait for the uuid_scan task to finish */
                down(&fs_info->uuid_tree_rescan_sem);
                /* avoid complains from lockdep et al. */
                up(&fs_info->uuid_tree_rescan_sem);

                btrfs_set_sb_rdonly(sb);

                /*
                 * Setting SB_RDONLY will put the cleaner thread to
                 * sleep at the next loop if it's already active.
                 * If it's already asleep, we'll leave unused block
                 * groups on disk until we're mounted read-write again
                 * unless we clean them up here.
                 */
                btrfs_delete_unused_bgs(fs_info);

                /*
                 * The cleaner task could be already running before we set the
                 * flag BTRFS_FS_STATE_RO (and SB_RDONLY in the superblock).
                 * We must make sure that after we finish the remount, i.e. after
                 * we call btrfs_commit_super(), the cleaner can no longer start
                 * a transaction - either because it was dropping a dead root,
                 * running delayed iputs or deleting an unused block group (the
                 * cleaner picked a block group from the list of unused block
                 * groups before we were able to in the previous call to
                 * btrfs_delete_unused_bgs()).
                 */
                wait_on_bit(&fs_info->flags, BTRFS_FS_CLEANER_RUNNING,
                            TASK_UNINTERRUPTIBLE);

                /*
                 * We've set the superblock to RO mode, so we might have made
                 * the cleaner task sleep without running all pending delayed
                 * iputs. Go through all the delayed iputs here, so that if an
                 * unmount happens without remounting RW we don't end up at
                 * finishing close_ctree() with a non-empty list of delayed
                 * iputs.
                 */
                btrfs_run_delayed_iputs(fs_info);

                btrfs_dev_replace_suspend_for_unmount(fs_info);
                btrfs_scrub_cancel(fs_info);
                btrfs_pause_balance(fs_info);

                /*
                 * Pause the qgroup rescan worker if it is running. We don't want
                 * it to be still running after we are in RO mode, as after that,
                 * by the time we unmount, it might have left a transaction open,

                 * so we would leak the transaction and/or crash.
                 */
                btrfs_qgroup_wait_for_completion(fs_info, false);

                ret = btrfs_commit_super(fs_info);
                if (ret)
                        goto restore;
        } else {
                if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
                        btrfs_err(fs_info,
                                "Remounting read-write after error is not allowed");
                        ret = -EINVAL;
                        goto restore;
                }
                if (fs_info->fs_devices->rw_devices == 0) {
                        ret = -EACCES;
                        goto restore;
                }

                if (!btrfs_check_rw_degradable(fs_info, NULL)) {
                        btrfs_warn(fs_info,
                "too many missing devices, writable remount is not allowed");
                        ret = -EACCES;
                        goto restore;
                }

                if (btrfs_super_log_root(fs_info->super_copy) != 0) {
                        btrfs_warn(fs_info,
                "mount required to replay tree-log, cannot remount read-write");
                        ret = -EINVAL;
                        goto restore;
                }

                /*
                 * NOTE: when remounting with a change that does writes, don't
                 * put it anywhere above this point, as we are not sure to be
                 * safe to write until we pass the above checks.
                 */
                ret = btrfs_start_pre_rw_mount(fs_info);
                if (ret)
                        goto restore;

                btrfs_clear_sb_rdonly(sb);

                set_bit(BTRFS_FS_OPEN, &fs_info->flags);
        }
out:
        /*
         * We need to set SB_I_VERSION here otherwise it'll get cleared by VFS,
         * since the absence of the flag means it can be toggled off by remount.
         */
        *flags |= SB_I_VERSION;

        wake_up_process(fs_info->transaction_kthread);
        btrfs_remount_cleanup(fs_info, old_opts);
        btrfs_clear_oneshot_options(fs_info);
        clear_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);

        return 0;

restore:
        /* We've hit an error - don't reset SB_RDONLY */
        if (sb_rdonly(sb))
                old_flags |= SB_RDONLY;
        if (!(old_flags & SB_RDONLY))
                clear_bit(BTRFS_FS_STATE_RO, &fs_info->fs_state);
        sb->s_flags = old_flags;
        fs_info->mount_opt = old_opts;
        fs_info->compress_type = old_compress_type;
        fs_info->max_inline = old_max_inline;
        btrfs_resize_thread_pool(fs_info,
                old_thread_pool_size, fs_info->thread_pool_size);
        fs_info->metadata_ratio = old_metadata_ratio;
        btrfs_remount_cleanup(fs_info, old_opts);
        clear_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);

        return ret;
}

/* Used to sort the devices by max_avail(descending sort) */
static int btrfs_cmp_device_free_bytes(const void *a, const void *b)
{
        const struct btrfs_device_info *dev_info1 = a;
        const struct btrfs_device_info *dev_info2 = b;

        if (dev_info1->max_avail > dev_info2->max_avail)
                return -1;
        else if (dev_info1->max_avail < dev_info2->max_avail)
                return 1;
        return 0;
}

/*
 * sort the devices by max_avail, in which max free extent size of each device
 * is stored.(Descending Sort)
 */
static inline void btrfs_descending_sort_devices(
                                        struct btrfs_device_info *devices,
                                        size_t nr_devices)
{
        sort(devices, nr_devices, sizeof(struct btrfs_device_info),
             btrfs_cmp_device_free_bytes, NULL);
}

/*
 * The helper to calc the free space on the devices that can be used to store
 * file data.
 */
static inline int btrfs_calc_avail_data_space(struct btrfs_fs_info *fs_info,
                                              u64 *free_bytes)
{
        struct btrfs_device_info *devices_info;
        struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
        struct btrfs_device *device;
        u64 type;
        u64 avail_space;
        u64 min_stripe_size;
        int num_stripes = 1;
        int i = 0, nr_devices;
        const struct btrfs_raid_attr *rattr;

        /*
         * We aren't under the device list lock, so this is racy-ish, but good
         * enough for our purposes.
         */
        nr_devices = fs_info->fs_devices->open_devices;
        if (!nr_devices) {
                smp_mb();
                nr_devices = fs_info->fs_devices->open_devices;
                ASSERT(nr_devices);
                if (!nr_devices) {
                        *free_bytes = 0;
                        return 0;
                }
        }

        devices_info = kmalloc_array(nr_devices, sizeof(*devices_info),
                               GFP_KERNEL);
        if (!devices_info)
                return -ENOMEM;

        /* calc min stripe number for data space allocation */
        type = btrfs_data_alloc_profile(fs_info);
        rattr = &btrfs_raid_array[btrfs_bg_flags_to_raid_index(type)];

        if (type & BTRFS_BLOCK_GROUP_RAID0)
                num_stripes = nr_devices;
        else if (type & BTRFS_BLOCK_GROUP_RAID1)
                num_stripes = 2;
        else if (type & BTRFS_BLOCK_GROUP_RAID1C3)
                num_stripes = 3;
        else if (type & BTRFS_BLOCK_GROUP_RAID1C4)
                num_stripes = 4;
        else if (type & BTRFS_BLOCK_GROUP_RAID10)
                num_stripes = 4;

        /* Adjust for more than 1 stripe per device */
        min_stripe_size = rattr->dev_stripes * BTRFS_STRIPE_LEN;

        rcu_read_lock();
        list_for_each_entry_rcu(device, &fs_devices->devices, dev_list) {
                if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
                                                &device->dev_state) ||
                    !device->bdev ||
                    test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state))
                        continue;

                if (i >= nr_devices)
                        break;

                avail_space = device->total_bytes - device->bytes_used;

                /* align with stripe_len */
                avail_space = rounddown(avail_space, BTRFS_STRIPE_LEN);

                /*
                 * In order to avoid overwriting the superblock on the drive,
                 * btrfs starts at an offset of at least 1MB when doing chunk
                 * allocation.
                 *
                 * This ensures we have at least min_stripe_size free space
                 * after excluding 1MB.
                 */
                if (avail_space <= SZ_1M + min_stripe_size)
                        continue;

                avail_space -= SZ_1M;

                devices_info[i].dev = device;
                devices_info[i].max_avail = avail_space;

                i++;
        }
        rcu_read_unlock();

        nr_devices = i;

        btrfs_descending_sort_devices(devices_info, nr_devices);

        i = nr_devices - 1;
        avail_space = 0;
        while (nr_devices >= rattr->devs_min) {
                num_stripes = min(num_stripes, nr_devices);

                if (devices_info[i].max_avail >= min_stripe_size) {
                        int j;
                        u64 alloc_size;

                        avail_space += devices_info[i].max_avail * num_stripes;
                        alloc_size = devices_info[i].max_avail;
                        for (j = i + 1 - num_stripes; j <= i; j++)
                                devices_info[j].max_avail -= alloc_size;
                }
                i--;
                nr_devices--;
        }

        kfree(devices_info);
        *free_bytes = avail_space;
        return 0;
}

/*
 * Calculate numbers for 'df', pessimistic in case of mixed raid profiles.
 *
 * If there's a redundant raid level at DATA block groups, use the respective
 * multiplier to scale the sizes.
 *
 * Unused device space usage is based on simulating the chunk allocator
 * algorithm that respects the device sizes and order of allocations.  This is
 * a close approximation of the actual use but there are other factors that may
 * change the result (like a new metadata chunk).
 *
 * If metadata is exhausted, f_bavail will be 0.
 */
static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(dentry->d_sb);
        struct btrfs_super_block *disk_super = fs_info->super_copy;
        struct btrfs_space_info *found;
        u64 total_used = 0;
        u64 total_free_data = 0;
        u64 total_free_meta = 0;
        u32 bits = fs_info->sectorsize_bits;
        __be32 *fsid = (__be32 *)fs_info->fs_devices->fsid;
        unsigned factor = 1;
        struct btrfs_block_rsv *block_rsv = &fs_info->global_block_rsv;
        int ret;
        u64 thresh = 0;
        int mixed = 0;

        list_for_each_entry(found, &fs_info->space_info, list) {
                if (found->flags & BTRFS_BLOCK_GROUP_DATA) {
                        int i;

                        total_free_data += found->disk_total - found->disk_used;
                        total_free_data -=
                                btrfs_account_ro_block_groups_free_space(found);

                        for (i = 0; i < BTRFS_NR_RAID_TYPES; i++) {
                                if (!list_empty(&found->block_groups[i]))
                                        factor = btrfs_bg_type_to_factor(
                                                btrfs_raid_array[i].bg_flag);
                        }
                }

                /*
                 * Metadata in mixed block goup profiles are accounted in data
                 */
                if (!mixed && found->flags & BTRFS_BLOCK_GROUP_METADATA) {
                        if (found->flags & BTRFS_BLOCK_GROUP_DATA)
                                mixed = 1;
                        else
                                total_free_meta += found->disk_total -
                                        found->disk_used;
                }

                total_used += found->disk_used;
        }

        buf->f_blocks = div_u64(btrfs_super_total_bytes(disk_super), factor);
        buf->f_blocks >>= bits;
        buf->f_bfree = buf->f_blocks - (div_u64(total_used, factor) >> bits);

        /* Account global block reserve as used, it's in logical size already */
        spin_lock(&block_rsv->lock);
        /* Mixed block groups accounting is not byte-accurate, avoid overflow */
        if (buf->f_bfree >= block_rsv->size >> bits)
                buf->f_bfree -= block_rsv->size >> bits;
        else
                buf->f_bfree = 0;
        spin_unlock(&block_rsv->lock);

        buf->f_bavail = div_u64(total_free_data, factor);
        ret = btrfs_calc_avail_data_space(fs_info, &total_free_data);
        if (ret)
                return ret;
        buf->f_bavail += div_u64(total_free_data, factor);
        buf->f_bavail = buf->f_bavail >> bits;

        /*
         * We calculate the remaining metadata space minus global reserve. If
         * this is (supposedly) smaller than zero, there's no space. But this
         * does not hold in practice, the exhausted state happens where's still
         * some positive delta. So we apply some guesswork and compare the
         * delta to a 4M threshold.  (Practically observed delta was ~2M.)
         *
         * We probably cannot calculate the exact threshold value because this
         * depends on the internal reservations requested by various
         * operations, so some operations that consume a few metadata will
         * succeed even if the Avail is zero. But this is better than the other
         * way around.
         */
        thresh = SZ_4M;

        /*
         * We only want to claim there's no available space if we can no longer
         * allocate chunks for our metadata profile and our global reserve will
         * not fit in the free metadata space.  If we aren't ->full then we
         * still can allocate chunks and thus are fine using the currently
         * calculated f_bavail.
         */
        if (!mixed && block_rsv->space_info->full &&
            total_free_meta - thresh < block_rsv->size)
                buf->f_bavail = 0;

        buf->f_type = BTRFS_SUPER_MAGIC;
        buf->f_bsize = dentry->d_sb->s_blocksize;
        buf->f_namelen = BTRFS_NAME_LEN;

        /* We treat it as constant endianness (it doesn't matter _which_)
           because we want the fsid to come out the same whether mounted
           on a big-endian or little-endian host */
        buf->f_fsid.val[0] = be32_to_cpu(fsid[0]) ^ be32_to_cpu(fsid[2]);
        buf->f_fsid.val[1] = be32_to_cpu(fsid[1]) ^ be32_to_cpu(fsid[3]);
        /* Mask in the root object ID too, to disambiguate subvols */
        buf->f_fsid.val[0] ^=
                BTRFS_I(d_inode(dentry))->root->root_key.objectid >> 32;
        buf->f_fsid.val[1] ^=
                BTRFS_I(d_inode(dentry))->root->root_key.objectid;

        return 0;
}

static void btrfs_kill_super(struct super_block *sb)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        kill_anon_super(sb);
        btrfs_free_fs_info(fs_info);
}

static struct file_system_type btrfs_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "btrfs",
        .mount          = btrfs_mount,
        .kill_sb        = btrfs_kill_super,
        .fs_flags       = FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA,
};

static struct file_system_type btrfs_root_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "btrfs",
        .mount          = btrfs_mount_root,
        .kill_sb        = btrfs_kill_super,
        .fs_flags       = FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA | FS_ALLOW_IDMAP,
};

MODULE_ALIAS_FS("btrfs");

static int btrfs_control_open(struct inode *inode, struct file *file)
{
        /*
         * The control file's private_data is used to hold the
         * transaction when it is started and is used to keep
         * track of whether a transaction is already in progress.
         */
        file->private_data = NULL;
        return 0;
}

/*
 * Used by /dev/btrfs-control for devices ioctls.
 */
static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
                                unsigned long arg)
{
        struct btrfs_ioctl_vol_args *vol;
        struct btrfs_device *device = NULL;
        int ret = -ENOTTY;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        vol = memdup_user((void __user *)arg, sizeof(*vol));
        if (IS_ERR(vol))
                return PTR_ERR(vol);
        vol->name[BTRFS_PATH_NAME_MAX] = '\0';

        switch (cmd) {
        case BTRFS_IOC_SCAN_DEV:
                mutex_lock(&uuid_mutex);
                device = btrfs_scan_one_device(vol->name, FMODE_READ,
                                               &btrfs_root_fs_type);
                ret = PTR_ERR_OR_ZERO(device);
                mutex_unlock(&uuid_mutex);
                break;
        case BTRFS_IOC_FORGET_DEV:
                ret = btrfs_forget_devices(vol->name);
                break;
        case BTRFS_IOC_DEVICES_READY:
                mutex_lock(&uuid_mutex);
                device = btrfs_scan_one_device(vol->name, FMODE_READ,
                                               &btrfs_root_fs_type);
                if (IS_ERR(device)) {
                        mutex_unlock(&uuid_mutex);
                        ret = PTR_ERR(device);
                        break;
                }
                ret = !(device->fs_devices->num_devices ==
                        device->fs_devices->total_devices);
                mutex_unlock(&uuid_mutex);
                break;
        case BTRFS_IOC_GET_SUPPORTED_FEATURES:
                ret = btrfs_ioctl_get_supported_features((void __user*)arg);
                break;
        }

        kfree(vol);
        return ret;
}

static int btrfs_freeze(struct super_block *sb)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        struct btrfs_root *root = fs_info->tree_root;

        set_bit(BTRFS_FS_FROZEN, &fs_info->flags);
        /*
         * We don't need a barrier here, we'll wait for any transaction that
         * could be in progress on other threads (and do delayed iputs that
         * we want to avoid on a frozen filesystem), or do the commit
         * ourselves.
         */
        trans = btrfs_attach_transaction_barrier(root);
        if (IS_ERR(trans)) {
                /* no transaction, don't bother */
                if (PTR_ERR(trans) == -ENOENT)
                        return 0;
                return PTR_ERR(trans);
        }
        return btrfs_commit_transaction(trans);
}

static int btrfs_unfreeze(struct super_block *sb)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);

        clear_bit(BTRFS_FS_FROZEN, &fs_info->flags);
        return 0;
}

static int btrfs_show_devname(struct seq_file *m, struct dentry *root)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(root->d_sb);
        struct btrfs_device *dev, *first_dev = NULL;

        /*
         * Lightweight locking of the devices. We should not need
         * device_list_mutex here as we only read the device data and the list
         * is protected by RCU.  Even if a device is deleted during the list
         * traversals, we'll get valid data, the freeing callback will wait at
         * least until the rcu_read_unlock.
         */
        rcu_read_lock();
        list_for_each_entry_rcu(dev, &fs_info->fs_devices->devices, dev_list) {
                if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state))
                        continue;
                if (!dev->name)
                        continue;
                if (!first_dev || dev->devid < first_dev->devid)
                        first_dev = dev;
        }

        if (first_dev)
                seq_escape(m, rcu_str_deref(first_dev->name), " \t\n\\");
        else
                WARN_ON(1);
        rcu_read_unlock();
        return 0;
}

static const struct super_operations btrfs_super_ops = {
        .drop_inode     = btrfs_drop_inode,
        .evict_inode    = btrfs_evict_inode,
        .put_super      = btrfs_put_super,
        .sync_fs        = btrfs_sync_fs,
        .show_options   = btrfs_show_options,
        .show_devname   = btrfs_show_devname,
        .alloc_inode    = btrfs_alloc_inode,
        .destroy_inode  = btrfs_destroy_inode,
        .free_inode     = btrfs_free_inode,
        .statfs         = btrfs_statfs,
        .remount_fs     = btrfs_remount,
        .freeze_fs      = btrfs_freeze,
        .unfreeze_fs    = btrfs_unfreeze,
};

static const struct file_operations btrfs_ctl_fops = {
        .open = btrfs_control_open,
        .unlocked_ioctl  = btrfs_control_ioctl,
        .compat_ioctl = compat_ptr_ioctl,
        .owner   = THIS_MODULE,
        .llseek = noop_llseek,
};

static struct miscdevice btrfs_misc = {
        .minor          = BTRFS_MINOR,
        .name           = "btrfs-control",
        .fops           = &btrfs_ctl_fops
};

MODULE_ALIAS_MISCDEV(BTRFS_MINOR);
MODULE_ALIAS("devname:btrfs-control");

static int __init btrfs_interface_init(void)
{
        return misc_register(&btrfs_misc);
}

static __cold void btrfs_interface_exit(void)
{
        misc_deregister(&btrfs_misc);
}

static void __init btrfs_print_mod_info(void)
{
        static const char options[] = ""
#ifdef CONFIG_BTRFS_DEBUG
                        ", debug=on"
#endif
#ifdef CONFIG_BTRFS_ASSERT
                        ", assert=on"
#endif
#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
                        ", integrity-checker=on"
#endif
#ifdef CONFIG_BTRFS_FS_REF_VERIFY
                        ", ref-verify=on"
#endif
#ifdef CONFIG_BLK_DEV_ZONED
                        ", zoned=yes"
#else
                        ", zoned=no"
#endif
#ifdef CONFIG_FS_VERITY
                        ", fsverity=yes"
#else
                        ", fsverity=no"
#endif
                        ;
        pr_info("Btrfs loaded, crc32c=%s%s\n", crc32c_impl(), options);
}

static int __init init_btrfs_fs(void)
{
        int err;

        btrfs_props_init();

        err = btrfs_init_sysfs();
        if (err)
                return err;

        btrfs_init_compress();

        err = btrfs_init_cachep();
        if (err)
                goto free_compress;

        err = extent_io_init();
        if (err)
                goto free_cachep;

        err = extent_state_cache_init();
        if (err)
                goto free_extent_io;

        err = extent_map_init();
        if (err)
                goto free_extent_state_cache;

        err = ordered_data_init();
        if (err)
                goto free_extent_map;

        err = btrfs_delayed_inode_init();
        if (err)
                goto free_ordered_data;

        err = btrfs_auto_defrag_init();
        if (err)
                goto free_delayed_inode;

        err = btrfs_delayed_ref_init();
        if (err)
                goto free_auto_defrag;

        err = btrfs_prelim_ref_init();
        if (err)
                goto free_delayed_ref;

        err = btrfs_end_io_wq_init();
        if (err)
                goto free_prelim_ref;

        err = btrfs_interface_init();
        if (err)
                goto free_end_io_wq;

        btrfs_print_mod_info();

        err = btrfs_run_sanity_tests();
        if (err)
                goto unregister_ioctl;

        err = register_filesystem(&btrfs_fs_type);
        if (err)
                goto unregister_ioctl;

        return 0;

unregister_ioctl:
        btrfs_interface_exit();
free_end_io_wq:
        btrfs_end_io_wq_exit();
free_prelim_ref:
        btrfs_prelim_ref_exit();
free_delayed_ref:
        btrfs_delayed_ref_exit();
free_auto_defrag:
        btrfs_auto_defrag_exit();
free_delayed_inode:
        btrfs_delayed_inode_exit();
free_ordered_data:
        ordered_data_exit();
free_extent_map:
        extent_map_exit();
free_extent_state_cache:
        extent_state_cache_exit();
free_extent_io:
        extent_io_exit();
free_cachep:
        btrfs_destroy_cachep();
free_compress:
        btrfs_exit_compress();
        btrfs_exit_sysfs();

        return err;
}

static void __exit exit_btrfs_fs(void)
{
        btrfs_destroy_cachep();
        btrfs_delayed_ref_exit();
        btrfs_auto_defrag_exit();
        btrfs_delayed_inode_exit();
        btrfs_prelim_ref_exit();
        ordered_data_exit();
        extent_map_exit();
        extent_state_cache_exit();
        extent_io_exit();
        btrfs_interface_exit();
        btrfs_end_io_wq_exit();
        unregister_filesystem(&btrfs_fs_type);
        btrfs_exit_sysfs();
        btrfs_cleanup_fs_uuids();
        btrfs_exit_compress();
}

late_initcall(init_btrfs_fs);
module_exit(exit_btrfs_fs)

MODULE_LICENSE("GPL");
MODULE_SOFTDEP("pre: crc32c");
MODULE_SOFTDEP("pre: xxhash64");
MODULE_SOFTDEP("pre: sha256");
MODULE_SOFTDEP("pre: blake2b-256");