[PATCH 2/2] block: fix blk_rq_append_bio

[Ming Lei <ming.lei@redhat.com>]

From: Jens Axboe <axboe@kernel.dk>

Commit caa4b02476e3(blk-map: call blk_queue_bounce from blk_rq_append_bio)
moves blk_queue_bounce() into blk_rq_append_bio(), but don't consider
that the bounced bio becomes invisiable to caller since the parameter type is
'struct bio *', which should have been 'struct bio **'.

This patch fixes this issue by passing 'struct bio **' to
blk_rq_append_bio(), then the bounced bio can be returned to caller.

Also failure handling is considered too.

Fixes: caa4b02476e3 ("blk-map: call blk_queue_bounce from blk_rq_append_bio")
Cc: Christoph Hellwig <hch@lst.de>
Reported-by: Michele Ballabio <barra_cuda@katamail.com>
(handling failure of blk_rq_append_bio(), only call bio_get() after
blk_rq_append_bio() returns OK)
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-map.c                    | 38 ++++++++++++++++++++++----------------
 drivers/scsi/osd/osd_initiator.c   |  4 +++-
 drivers/target/target_core_pscsi.c |  4 ++--
 include/linux/blkdev.h             |  2 +-
 4 files changed, 28 insertions(+), 20 deletions(-)

diff --git a/block/blk-map.c b/block/blk-map.c
index b21f8e86f120..d3a94719f03f 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -12,22 +12,29 @@
 #include "blk.h"
 
 /*
- * Append a bio to a passthrough request.  Only works can be merged into
- * the request based on the driver constraints.
+ * Append a bio to a passthrough request.  Only works if the bio can be merged
+ * into the request based on the driver constraints.
  */
-int blk_rq_append_bio(struct request *rq, struct bio *bio)
+int blk_rq_append_bio(struct request *rq, struct bio **bio)
 {
-	blk_queue_bounce(rq->q, &bio);
+	struct bio *orig_bio = *bio;
+
+	blk_queue_bounce(rq->q, bio);
 
 	if (!rq->bio) {
-		blk_rq_bio_prep(rq->q, rq, bio);
+		blk_rq_bio_prep(rq->q, rq, *bio);
 	} else {
-		if (!ll_back_merge_fn(rq->q, rq, bio))
+		if (!ll_back_merge_fn(rq->q, rq, *bio)) {
+			if (orig_bio != *bio) {
+				bio_put(*bio);
+				*bio = orig_bio;
+			}
 			return -EINVAL;
+		}
 
-		rq->biotail->bi_next = bio;
-		rq->biotail = bio;
-		rq->__data_len += bio->bi_iter.bi_size;
+		rq->biotail->bi_next = *bio;
+		rq->biotail = *bio;
+		rq->__data_len += (*bio)->bi_iter.bi_size;
 	}
 
 	return 0;
@@ -73,14 +80,12 @@ static int __blk_rq_map_user_iov(struct request *rq,
 	 * We link the bounce buffer in and could have to traverse it
 	 * later so we have to get a ref to prevent it from being freed
 	 */
-	ret = blk_rq_append_bio(rq, bio);
-	bio_get(bio);
+	ret = blk_rq_append_bio(rq, &bio);
 	if (ret) {
-		bio_endio(bio);
 		__blk_rq_unmap_user(orig_bio);
-		bio_put(bio);
 		return ret;
 	}
+	bio_get(bio);
 
 	return 0;
 }
@@ -213,7 +218,7 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 	int reading = rq_data_dir(rq) == READ;
 	unsigned long addr = (unsigned long) kbuf;
 	int do_copy = 0;
-	struct bio *bio;
+	struct bio *bio, *orig_bio;
 	int ret;
 
 	if (len > (queue_max_hw_sectors(q) << 9))
@@ -236,10 +241,11 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 	if (do_copy)
 		rq->rq_flags |= RQF_COPY_USER;
 
-	ret = blk_rq_append_bio(rq, bio);
+	orig_bio = bio;
+	ret = blk_rq_append_bio(rq, &bio);
 	if (unlikely(ret)) {
 		/* request is too big */
-		bio_put(bio);
+		bio_put(orig_bio);
 		return ret;
 	}
 
diff --git a/drivers/scsi/osd/osd_initiator.c b/drivers/scsi/osd/osd_initiator.c
index a4f28b7e4c65..e18877177f1b 100644
--- a/drivers/scsi/osd/osd_initiator.c
+++ b/drivers/scsi/osd/osd_initiator.c
@@ -1576,7 +1576,9 @@ static struct request *_make_request(struct request_queue *q, bool has_write,
 		return req;
 
 	for_each_bio(bio) {
-		ret = blk_rq_append_bio(req, bio);
+		struct bio *bounce_bio = bio;
+
+		ret = blk_rq_append_bio(req, &bounce_bio);
 		if (ret)
 			return ERR_PTR(ret);
 	}
diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index 7c69b4a9694d..0d99b242e82e 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -920,7 +920,7 @@ pscsi_map_sg(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 					" %d i: %d bio: %p, allocating another"
 					" bio\n", bio->bi_vcnt, i, bio);
 
-				rc = blk_rq_append_bio(req, bio);
+				rc = blk_rq_append_bio(req, &bio);
 				if (rc) {
 					pr_err("pSCSI: failed to append bio\n");
 					goto fail;
@@ -938,7 +938,7 @@ pscsi_map_sg(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 	}
 
 	if (bio) {
-		rc = blk_rq_append_bio(req, bio);
+		rc = blk_rq_append_bio(req, &bio);
 		if (rc) {
 			pr_err("pSCSI: failed to append bio\n");
 			goto fail;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index abd06f540863..100d0df38026 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -965,7 +965,7 @@ extern int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
 extern void blk_rq_unprep_clone(struct request *rq);
 extern blk_status_t blk_insert_cloned_request(struct request_queue *q,
 				     struct request *rq);
-extern int blk_rq_append_bio(struct request *rq, struct bio *bio);
+extern int blk_rq_append_bio(struct request *rq, struct bio **bio);
 extern void blk_delay_queue(struct request_queue *, unsigned long);
 extern void blk_queue_split(struct request_queue *, struct bio **);
 extern void blk_recount_segments(struct request_queue *, struct bio *);
-- 
2.9.5