diff options
| author | Omar Sandoval <osandov@osandov.com> | 2015-05-18 12:16:26 +0300 |
|---|---|---|
| committer | Luis Henriques <luis.henriques@canonical.com> | 2015-07-15 12:01:24 +0300 |
| commit | 7af6355eea6e842122018f094e2ff8ed9df39496 (patch) | |
| tree | 53c2d966a71bb5e388adaba36ddcef3e04ce0ee6 /fs/btrfs | |
| parent | c0f611d673cf1d2838890159d8d801ca8ed6752c (diff) | |
| download | linux-7af6355eea6e842122018f094e2ff8ed9df39496.tar.xz | |
Btrfs: lock superblock before remounting for rw subvol
commit 773cd04ec1911abb33cf9538b65f55b76cad5d92 upstream.
Since commit 0723a0473fb4 ("btrfs: allow mounting btrfs subvolumes with
different ro/rw options"), when mounting a subvolume read/write when
another subvolume has previously been mounted read-only, we first do a
remount. However, this should be done with the superblock locked, as per
sync_filesystem():
/*
* We need to be protected against the filesystem going from
* r/o to r/w or vice versa.
*/
WARN_ON(!rwsem_is_locked(&sb->s_umount));
This WARN_ON can easily be hit with:
mkfs.btrfs -f /dev/vdb
mount /dev/vdb /mnt
btrfs subvol create /mnt/vol1
btrfs subvol create /mnt/vol2
umount /mnt
mount -oro,subvol=/vol1 /dev/vdb /mnt
mount -orw,subvol=/vol2 /dev/vdb /mnt2
Fixes: 0723a0473fb4 ("btrfs: allow mounting btrfs subvolumes with different ro/rw options")
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Diffstat (limited to 'fs/btrfs')
| -rw-r--r-- | fs/btrfs/super.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 600035120ca3..863f3d65fe39 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1203,7 +1203,9 @@ static struct dentry *mount_subvol(const char *subvol_name, int flags, return ERR_CAST(mnt); } + down_write(&mnt->mnt_sb->s_umount); r = btrfs_remount(mnt->mnt_sb, &flags, NULL); + up_write(&mnt->mnt_sb->s_umount); if (r < 0) { /* FIXME: release vfsmount mnt ??*/ kfree(newargs); |