| Message ID | ad0f1a6b626ecc879bd23972869c8ab93e0312d0.1428614837.git.osandov@osandov.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Thu, Apr 09, 2015 at 02:34:51PM -0700, Omar Sandoval wrote: > 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") > Signed-off-by: Omar Sandoval <osandov@osandov.com> Reviewed-by: David Sterba <dsterba@suse.cz> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 05fef19..d38be09 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1205,7 +1205,9 @@ 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);
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") Signed-off-by: Omar Sandoval <osandov@osandov.com> --- fs/btrfs/super.c | 2 ++ 1 file changed, 2 insertions(+)