[PATCH v2 2/2] ext4: improve error msg for ext4_mb_seq_groups_show

[yangerkun <yangerkun@huawei.com>]

While cat mb_groups for a mounted ext4 image which has some corrupted
group, the string return to userspace was just "I/O error" which confuse
me a lot. Improve it with ext4_decode_error.

Signed-off-by: yangerkun <yangerkun@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/mballoc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

v1-v2:
improve the commit msg, add review tag.

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 866f8f0922f1..f0c79c9d35e1 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2991,6 +2991,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
 	struct super_block *sb = pde_data(file_inode(seq->file));
 	ext4_group_t group = (ext4_group_t) ((unsigned long) v);
 	int i, err;
+	char nbuf[16];
 	struct ext4_buddy e4b;
 	struct ext4_group_info *grinfo;
 	unsigned char blocksize_bits = min_t(unsigned char,
@@ -3017,7 +3018,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
 	if (unlikely(EXT4_MB_GRP_NEED_INIT(grinfo))) {
 		err = ext4_mb_load_buddy(sb, group, &e4b);
 		if (err) {
-			seq_printf(seq, "#%-5u: I/O error\n", group);
+			seq_printf(seq, "#%-5u: %s\n", group, ext4_decode_error(NULL, err, nbuf));
 			return 0;
 		}
 		ext4_mb_unload_buddy(&e4b);
-- 
2.39.2