From: Qu Wenruo <wqu@xxxxxxxx> commit d5321a0fa8bc49f11bea0b470800962c17d92d8f upstream. The following error message lack the "0x" obviously: cannot mount because of unsupported optional features (4000) Add the prefix to make it less confusing. This can happen on older kernels that try to mount a filesystem with newer features so it makes sense to backport to older trees. CC: stable@xxxxxxxxxxxxxxx # 4.14+ Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx> 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/disk-io.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -2927,7 +2927,7 @@ int open_ctree(struct super_block *sb, ~BTRFS_FEATURE_INCOMPAT_SUPP; if (features) { btrfs_err(fs_info, - "cannot mount because of unsupported optional features (%llx)", + "cannot mount because of unsupported optional features (0x%llx)", features); err = -EINVAL; goto fail_csum; @@ -2965,7 +2965,7 @@ int open_ctree(struct super_block *sb, ~BTRFS_FEATURE_COMPAT_RO_SUPP; if (!sb_rdonly(sb) && features) { btrfs_err(fs_info, - "cannot mount read-write because of unsupported optional features (%llx)", + "cannot mount read-write because of unsupported optional features (0x%llx)", features); err = -EINVAL; goto fail_csum;