From: Greg Kroah-Hartman gregkh@linuxfoundation.org
From: Boris Burkov boris@bur.io
commit c55a4319c4f2c3ba0a385b1ebc454fa283cfe920 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/super.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1919,8 +1919,8 @@ static int btrfs_remount(struct super_bl 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");