Btrfs: fix unexpected result when dio reading corrupted blocks

commit 4246a0b6 ("block: add a bi_error field to struct bio")
changed the logic of how dio read endio reports errors.

For single stripe dio read, %bio->bi_status reflects the error before
verifying checksum, and now we're updating it when data block matches
with its checksum, while in the mismatching case, %bio->bi_status is
not updated to relfect that.

When some blocks in a file have been corrupted on disk, reading such a
file ends up with

1) checksum errors are reported in kernel log
2) read(2) returns successfully with some content being 0x01.

In order to fix it, we need to report its checksum mismatch error to
the upper layer (dio layer in this case) as well.

Fixes: 4246a0b6 ("block: add a bi_error field to struct bio")
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reported-by: Goffredo Baroncelli <kreijack@inwind.it>
Tested-by: Goffredo Baroncelli <kreijack@inwind.it>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -8366,11 +8366,8 @@ static void btrfs_endio_direct_read(struct bio *bio)
 	struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
 	blk_status_t err = bio->bi_status;
 
-	if (dip->flags & BTRFS_DIO_ORIG_BIO_SUBMITTED) {
+	if (dip->flags & BTRFS_DIO_ORIG_BIO_SUBMITTED)
 		err = btrfs_subio_endio_read(inode, io_bio, err);
-		if (!err)
-			bio->bi_status = 0;
-	}
 
 	unlock_extent(&BTRFS_I(inode)->io_tree, dip->logical_offset,
 		      dip->logical_offset + dip->bytes - 1);
@@ -8378,7 +8375,7 @@ static void btrfs_endio_direct_read(struct bio *bio)
 
 	kfree(dip);
 
-	dio_bio->bi_status = bio->bi_status;
+	dio_bio->bi_status = err;
 	dio_end_io(dio_bio);
 
 	if (io_bio->end_io)