/*
 *  linux/fs/fat/file.c
 *
 *  Written 1992,1993 by Werner Almesberger
 *
 *  regular file handling primitives for fat-based filesystems
 */

#include <linux/capability.h>
#include <linux/module.h>
#include <linux/compat.h>
#include <linux/mount.h>
#include <linux/time.h>
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include <linux/backing-dev.h>
#include <linux/blkdev.h>
#include <linux/fsnotify.h>
#include <linux/security.h>
#include "fat.h"

static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
{
        u32 attr;

        mutex_lock(&inode->i_mutex);
        attr = fat_make_attrs(inode);
        mutex_unlock(&inode->i_mutex);

        return put_user(attr, user_attr);
}

static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
{
        struct inode *inode = file_inode(file);
        struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
        int is_dir = S_ISDIR(inode->i_mode);
        u32 attr, oldattr;
        struct iattr ia;
        int err;

        err = get_user(attr, user_attr);
        if (err)
                goto out;

        err = mnt_want_write_file(file);
        if (err)
                goto out;
        mutex_lock(&inode->i_mutex);

        /*
         * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
         * prevents the user from turning us into a VFAT
         * longname entry.  Also, we obviously can't set
         * any of the NTFS attributes in the high 24 bits.
         */
        attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
        /* Merge in ATTR_VOLUME and ATTR_DIR */
        attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
                (is_dir ? ATTR_DIR : 0);
        oldattr = fat_make_attrs(inode);

        /* Equivalent to a chmod() */
        ia.ia_valid = ATTR_MODE | ATTR_CTIME;
        ia.ia_ctime = current_fs_time(inode->i_sb);
        if (is_dir)
                ia.ia_mode = fat_make_mode(sbi, attr, S_IRWXUGO);
        else {
                ia.ia_mode = fat_make_mode(sbi, attr,
                        S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO));
        }

        /* The root directory has no attributes */
        if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
                err = -EINVAL;
                goto out_unlock_inode;
        }

        if (sbi->options.sys_immutable &&
            ((attr | oldattr) & ATTR_SYS) &&
            !capable(CAP_LINUX_IMMUTABLE)) {
                err = -EPERM;
                goto out_unlock_inode;
        }

        /*
         * The security check is questionable...  We single
         * out the RO attribute for checking by the security
         * module, just because it maps to a file mode.
         */
        err = security_inode_setattr(file->f_path.dentry, &ia);
        if (err)
                goto out_unlock_inode;

        /* This MUST be done before doing anything irreversible... */
        err = fat_setattr(file->f_path.dentry, &ia);
        if (err)
                goto out_unlock_inode;

        fsnotify_change(file->f_path.dentry, ia.ia_valid);
        if (sbi->options.sys_immutable) {
                if (attr & ATTR_SYS)
                        inode->i_flags |= S_IMMUTABLE;
                else
                        inode->i_flags &= ~S_IMMUTABLE;
        }

        fat_save_attrs(inode, attr);
        mark_inode_dirty(inode);
out_unlock_inode:
        mutex_unlock(&inode->i_mutex);
        mnt_drop_write_file(file);
out:
        return err;
}

static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
{
        struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
        return put_user(sbi->vol_id, user_attr);
}

long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
        struct inode *inode = file_inode(filp);
        u32 __user *user_attr = (u32 __user *)arg;

        switch (cmd) {
        case FAT_IOCTL_GET_ATTRIBUTES:
                return fat_ioctl_get_attributes(inode, user_attr);
        case FAT_IOCTL_SET_ATTRIBUTES:
                return fat_ioctl_set_attributes(filp, user_attr);
        case FAT_IOCTL_GET_VOLUME_ID:
                return fat_ioctl_get_volume_id(inode, user_attr);
        default:
                return -ENOTTY; /* Inappropriate ioctl for device */
        }
}

#ifdef CONFIG_COMPAT
static long fat_generic_compat_ioctl(struct file *filp, unsigned int cmd,
                                      unsigned long arg)

{
        return fat_generic_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
}
#endif

static int fat_file_release(struct inode *inode, struct file *filp)
{
        if ((filp->f_mode & FMODE_WRITE) &&
             MSDOS_SB(inode->i_sb)->options.flush) {
                fat_flush_inodes(inode->i_sb, inode, NULL);
                congestion_wait(BLK_RW_ASYNC, HZ/10);
        }
        return 0;
}

int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
{
        struct inode *inode = filp->f_mapping->host;
        int res, err;

        res = generic_file_fsync(filp, start, end, datasync);
        err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);

        return res ? res : err;
}


const struct file_operations fat_file_operations = {
        .llseek         = generic_file_llseek,
        .read           = new_sync_read,
        .write          = new_sync_write,
        .read_iter      = generic_file_read_iter,
        .write_iter     = generic_file_write_iter,
        .mmap           = generic_file_mmap,
        .release        = fat_file_release,
        .unlocked_ioctl = fat_generic_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = fat_generic_compat_ioctl,
#endif
        .fsync          = fat_file_fsync,
        .splice_read    = generic_file_splice_read,
};

static int fat_cont_expand(struct inode *inode, loff_t size)
{
        struct address_space *mapping = inode->i_mapping;
        loff_t start = inode->i_size, count = size - inode->i_size;
        int err;

        err = generic_cont_expand_simple(inode, size);
        if (err)
                goto out;

        inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
        mark_inode_dirty(inode);
        if (IS_SYNC(inode)) {
                int err2;

                /*
                 * Opencode syncing since we don't have a file open to use
                 * standard fsync path.
                 */
                err = filemap_fdatawrite_range(mapping, start,
                                               start + count - 1);
                err2 = sync_mapping_buffers(mapping);
                if (!err)
                        err = err2;
                err2 = write_inode_now(inode, 1);
                if (!err)
                        err = err2;
                if (!err) {
                        err =  filemap_fdatawait_range(mapping, start,
                                                       start + count - 1);
                }
        }
out:
        return err;
}

/* Free all clusters after the skip'th cluster. */
static int fat_free(struct inode *inode, int skip)
{
        struct super_block *sb = inode->i_sb;
        int err, wait, free_start, i_start, i_logstart;

        if (MSDOS_I(inode)->i_start == 0)
                return 0;

        fat_cache_inval_inode(inode);

        wait = IS_DIRSYNC(inode);
        i_start = free_start = MSDOS_I(inode)->i_start;
        i_logstart = MSDOS_I(inode)->i_logstart;

        /* First, we write the new file size. */
        if (!skip) {
                MSDOS_I(inode)->i_start = 0;
                MSDOS_I(inode)->i_logstart = 0;
        }
        MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
        inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
        if (wait) {
                err = fat_sync_inode(inode);
                if (err) {
                        MSDOS_I(inode)->i_start = i_start;
                        MSDOS_I(inode)->i_logstart = i_logstart;
                        return err;
                }
        } else
                mark_inode_dirty(inode);

        /* Write a new EOF, and get the remaining cluster chain for freeing. */
        if (skip) {
                struct fat_entry fatent;
                int ret, fclus, dclus;

                ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
                if (ret < 0)
                        return ret;
                else if (ret == FAT_ENT_EOF)
                        return 0;

                fatent_init(&fatent);
                ret = fat_ent_read(inode, &fatent, dclus);
                if (ret == FAT_ENT_EOF) {
                        fatent_brelse(&fatent);
                        return 0;
                } else if (ret == FAT_ENT_FREE) {
                        fat_fs_error(sb,
                                     "%s: invalid cluster chain (i_pos %lld)",
                                     __func__, MSDOS_I(inode)->i_pos);
                        ret = -EIO;
                } else if (ret > 0) {
                        err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
                        if (err)
                                ret = err;
                }
                fatent_brelse(&fatent);
                if (ret < 0)
                        return ret;

                free_start = ret;
        }
        inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);

        /* Freeing the remained cluster chain */
        return fat_free_clusters(inode, free_start);
}

void fat_truncate_blocks(struct inode *inode, loff_t offset)
{
        struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
        const unsigned int cluster_size = sbi->cluster_size;
        int nr_clusters;

        /*
         * This protects against truncating a file bigger than it was then
         * trying to write into the hole.
         */
        if (MSDOS_I(inode)->mmu_private > offset)
                MSDOS_I(inode)->mmu_private = offset;

        nr_clusters = (offset + (cluster_size - 1)) >> sbi->cluster_bits;

        fat_free(inode, nr_clusters);
        fat_flush_inodes(inode->i_sb, inode, NULL);
}

int fat_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
{
        struct inode *inode = dentry->d_inode;
        generic_fillattr(inode, stat);
        stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;

        if (MSDOS_SB(inode->i_sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
                /* Use i_pos for ino. This is used as fileid of nfs. */
                stat->ino = fat_i_pos_read(MSDOS_SB(inode->i_sb), inode);
        }
        return 0;
}
EXPORT_SYMBOL_GPL(fat_getattr);

static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
                             struct inode *inode, umode_t *mode_ptr)
{
        umode_t mask, perm;

        /*
         * Note, the basic check is already done by a caller of
         * (attr->ia_mode & ~FAT_VALID_MODE)
         */

        if (S_ISREG(inode->i_mode))
                mask = sbi->options.fs_fmask;
        else
                mask = sbi->options.fs_dmask;

        perm = *mode_ptr & ~(S_IFMT | mask);

        /*
         * Of the r and x bits, all (subject to umask) must be present. Of the
         * w bits, either all (subject to umask) or none must be present.
         *
         * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
         */
        if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
                return -EPERM;
        if (fat_mode_can_hold_ro(inode)) {
                if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
                        return -EPERM;
        } else {
                if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
                        return -EPERM;
        }

        *mode_ptr &= S_IFMT | perm;

        return 0;
}

static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode)
{
        umode_t allow_utime = sbi->options.allow_utime;

        if (!uid_eq(current_fsuid(), inode->i_uid)) {
                if (in_group_p(inode->i_gid))
                        allow_utime >>= 3;
                if (allow_utime & MAY_WRITE)
                        return 1;
        }

        /* use a default check */
        return 0;
}

#define TIMES_SET_FLAGS (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
/* valid file mode bits */
#define FAT_VALID_MODE  (S_IFREG | S_IFDIR | S_IRWXUGO)

int fat_setattr(struct dentry *dentry, struct iattr *attr)
{
        struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
        struct inode *inode = dentry->d_inode;
        unsigned int ia_valid;
        int error;

        /* Check for setting the inode time. */
        ia_valid = attr->ia_valid;
        if (ia_valid & TIMES_SET_FLAGS) {
                if (fat_allow_set_time(sbi, inode))
                        attr->ia_valid &= ~TIMES_SET_FLAGS;
        }

        error = inode_change_ok(inode, attr);
        attr->ia_valid = ia_valid;
        if (error) {
                if (sbi->options.quiet)
                        error = 0;
                goto out;
        }

        /*
         * Expand the file. Since inode_setattr() updates ->i_size
         * before calling the ->truncate(), but FAT needs to fill the
         * hole before it. XXX: this is no longer true with new truncate
         * sequence.
         */
        if (attr->ia_valid & ATTR_SIZE) {
                inode_dio_wait(inode);

                if (attr->ia_size > inode->i_size) {
                        error = fat_cont_expand(inode, attr->ia_size);
                        if (error || attr->ia_valid == ATTR_SIZE)
                                goto out;
                        attr->ia_valid &= ~ATTR_SIZE;
                }
        }

        if (((attr->ia_valid & ATTR_UID) &&
             (!uid_eq(attr->ia_uid, sbi->options.fs_uid))) ||
            ((attr->ia_valid & ATTR_GID) &&
             (!gid_eq(attr->ia_gid, sbi->options.fs_gid))) ||
            ((attr->ia_valid & ATTR_MODE) &&
             (attr->ia_mode & ~FAT_VALID_MODE)))
                error = -EPERM;

        if (error) {
                if (sbi->options.quiet)
                        error = 0;
                goto out;
        }

        /*
         * We don't return -EPERM here. Yes, strange, but this is too
         * old behavior.
         */
        if (attr->ia_valid & ATTR_MODE) {
                if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
                        attr->ia_valid &= ~ATTR_MODE;
        }

        if (attr->ia_valid & ATTR_SIZE) {
                down_write(&MSDOS_I(inode)->truncate_lock);
                truncate_setsize(inode, attr->ia_size);
                fat_truncate_blocks(inode, attr->ia_size);
                up_write(&MSDOS_I(inode)->truncate_lock);
        }

        setattr_copy(inode, attr);
        mark_inode_dirty(inode);
out:
        return error;
}
EXPORT_SYMBOL_GPL(fat_setattr);

const struct inode_operations fat_file_inode_operations = {
        .setattr        = fat_setattr,
        .getattr        = fat_getattr,
};