From: Qu Wenruo <wqu@xxxxxxxx> commit 0591f04036218d572d54349ea8c7914ad9c82b2b upstream. Upstream commit 9f73f1aef98b ("btrfs: force v2 space cache usage for subpage mount") forces subpage mount to use v2 cache, to avoid deprecated v1 cache which doesn't support subpage properly. But there is a loophole that user can still remount to v1 cache. The existing check will only give users a warning, but does not really prevent to do the remount. Although remounting to v1 will not cause any problems since the v1 cache will always be marked invalid when mounted with a different page size, it's still better to prevent v1 cache at all for subpage mounts. Fixes: 9f73f1aef98b ("btrfs: force v2 space cache usage for subpage mount") CC: stable@xxxxxxxxxxxxxxx # 5.15+ Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> Reviewed-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/btrfs/super.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1917,6 +1917,14 @@ static int btrfs_remount(struct super_bl if (ret) goto restore; + /* V1 cache is not supported for subpage mount. */ + if (fs_info->sectorsize < PAGE_SIZE && btrfs_test_opt(fs_info, SPACE_CACHE)) { + btrfs_warn(fs_info, + "v1 space cache is not supported for page size %lu with sectorsize %u", + PAGE_SIZE, fs_info->sectorsize); + ret = -EINVAL; + goto restore; + } btrfs_remount_begin(fs_info, old_opts, *flags); btrfs_resize_thread_pool(fs_info, fs_info->thread_pool_size, old_thread_pool_size);