iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

btrfs: fix spurious free_space_tree remount warning

Browse Source 
The intended logic of the check is to catch cases where the desired
free_space_tree setting doesn't match the mounted setting, and the
remount is anything but ro->rw. However, it makes the mistake of
checking equality on a masked integer (btrfs_test_opt) against a boolean
(btrfs_fs_compat_ro).

If you run the reproducer:
  $ mount -o space_cache=v2 dev mnt
  $ mount -o remount,ro mnt

you would expect no warning, because the remount is not attempting to
change the free space tree setting, but we do see the warning.

To fix this, add explicit bool type casts to the condition.

I tested a variety of transitions:
sudo mount -o space_cache=v2 /dev/vg0/lv0 mnt/lol
(fst enabled)
mount -o remount,ro mnt/lol
(no warning, no fst change)
sudo mount -o remount,rw,space_cache=v1,clear_cache
(no warning, ro->rw)
sudo mount -o remount,rw,space_cache=v2 mnt
(warning, rw->rw with change)
sudo mount -o remount,ro mnt
(no warning, no fst change)
sudo mount -o remount,rw,space_cache=v2 mnt
(no warning, no fst change)

Reported-by: Chris Murphy <lists@colorremedies.com>
CC: stable@vger.kernel.org # 5.11
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Boris Burkov 2021-02-23 10:22:32 -08:00 committed by David Sterba
parent 5011c5a663
commit c55a4319c4
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/btrfs/super.c
View File

@ -1918,8 +1918,8 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
btrfs_resize_thread_pool(fs_info,
fs_info->thread_pool_size, old_thread_pool_size);
if (btrfs_test_opt(fs_info, FREE_SPACE_TREE) !=
btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE) &&
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");