[PATCH v2] ext4: report unwritten extent conversion failures as writeback errors

[guolingxing]

When a data writeback bio completes successfully but the subsequent
unwritten extent conversion fails, ext4_end_io_end() does not record
the error in the inode's mapping writeback error state.

Bio failures are already recorded by ext4_end_bio(), but conversion
failures are not. When the conversion is processed asynchronously,
its return value is not propagated to userspace, so fsync() may
return success despite the failed conversion.

Record conversion errors with mapping_set_error() before
ext4_release_io_end() ends folio writeback and wakes waiters. This
allows fsync() to observe the failure.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: guolingxing <guolingxing@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
---
Changes since v1:
- Drop the incorrect Fixes tag. The conversion error was already lost
  before commit b82e384c7bb9, as pointed out by Jan Kara.
- Collect Reviewed-by from Jan Kara.

 fs/ext4/page-io.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 734d856a6d478..2701452fa65ca 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -192,6 +192,8 @@ static int ext4_end_io_end(ext4_io_end_t *io_end)
 			jbd2_journal_abort(EXT4_SB(sb)->s_journal, ret);
 	} else {
 		ret = ext4_convert_unwritten_io_end_vec(handle, io_end);
+		if (ret < 0)
+			mapping_set_error(inode->i_mapping, ret);
 	}
 	if (ret < 0 && !ext4_emergency_state(sb) &&
 	    io_end->flag & EXT4_IO_END_UNWRITTEN) {
-- 
2.34.1