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| author | Omar Sandoval | 2015-05-18 11:16:26 +0200 |
|---|---|---|
| committer | Chris Mason | 2015-06-03 13:02:57 +0200 |
| commit | 773cd04ec1911abb33cf9538b65f55b76cad5d92 (patch) | |
| tree | b41feb18b6ba9694cf5d255d8994b6851e46868e | |
| parent | Btrfs: wake up extent state waiters on unlock through clear_extent_bits (diff) | |
| download | kernel-qcow2-linux-773cd04ec1911abb33cf9538b65f55b76cad5d92.tar.gz kernel-qcow2-linux-773cd04ec1911abb33cf9538b65f55b76cad5d92.tar.xz kernel-qcow2-linux-773cd04ec1911abb33cf9538b65f55b76cad5d92.zip | |
Btrfs: lock superblock before remounting for rw subvol
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>
| -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 c761d8e068e8..93f2edf6b603 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1209,7 +1209,9 @@ 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); |