erofs: handle end of filesystem properly for file-backed mounts

I/O requests beyond the end of the filesystem should be zeroed out,
similar to loopback devices and that is what we expect.

Fixes: ce63cb6 ("erofs: support unencoded inodes for fileio")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Author: hsiangkao

fs/erofs/fileio.c

@@ -24,21 +24,17 @@ static void erofs_fileio_ki_complete(struct kiocb *iocb, long ret)
 			container_of(iocb, struct erofs_fileio_rq, iocb);
 	struct folio_iter fi;
 
-	if (ret > 0) {
-		if (ret != rq->bio.bi_iter.bi_size) {
-			bio_advance(&rq->bio, ret);
-			zero_fill_bio(&rq->bio);
-		}
-		ret = 0;
+	if (ret >= 0 && ret != rq->bio.bi_iter.bi_size) {
+		bio_advance(&rq->bio, ret);
+		zero_fill_bio(&rq->bio);
 	}
-	if (rq->bio.bi_end_io) {
-		if (ret < 0 && !rq->bio.bi_status)
-			rq->bio.bi_status = errno_to_blk_status(ret);
-	} else {
+	if (!rq->bio.bi_end_io) {
 		bio_for_each_folio_all(fi, &rq->bio) {
 			DBG_BUGON(folio_test_uptodate(fi.folio));
-			erofs_onlinefolio_end(fi.folio, ret, false);
+			erofs_onlinefolio_end(fi.folio, ret < 0, false);
 		}
+	} else if (ret < 0 && !rq->bio.bi_status) {
+		rq->bio.bi_status = errno_to_blk_status(ret);
 	}
 	bio_endio(&rq->bio);
 	bio_uninit(&rq->bio);
@@ -48,7 +44,7 @@ static void erofs_fileio_ki_complete(struct kiocb *iocb, long ret)
 static void erofs_fileio_rq_submit(struct erofs_fileio_rq *rq)
 {
 	struct iov_iter iter;
-	int ret;
+	ssize_t ret;
 
 	if (!rq)
 		return;