From: Ming Lei <ming.lei@redhat.com>
Date: Mon, 18 Dec 2017 15:40:43 +0800
Subject: [PATCH] block: don't let passthrough IO go into .make_request_fn()
References: bsc#1077989
Git-commit: 14cb0dc6479dc5ebc63b3a459a5d89a2f1b39fed
Patch-mainline: v4.15-rc5

Commit a8821f3f3("block: Improvements to bounce-buffer handling") tries
to make sure that the bio to .make_request_fn won't exceed BIO_MAX_PAGES,
but ignores that passthrough I/O can use blk_queue_bounce() too.
Especially, passthrough IO may not be sector-aligned, and the check
of 'sectors < bio_sectors(*bio_orig)' inside __blk_queue_bounce() may
become true even though the max bvec number doesn't exceed BIO_MAX_PAGES,
then cause the bio splitted, and the original passthrough bio is submited
to generic_make_request().

This patch fixes this issue by checking if the bio is passthrough IO,
and use bio_kmalloc() to allocate the cloned passthrough bio.

Cc: NeilBrown <neilb@suse.com>
Fixes: a8821f3f3("block: Improvements to bounce-buffer handling")
Tested-by: Michele Ballabio <barra_cuda@katamail.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 block/bounce.c         |  6 ++++--
 include/linux/blkdev.h | 21 +++++++++++++++++++--
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/block/bounce.c b/block/bounce.c
index 5793c2dc1a15..c91f32d78819 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -199,6 +199,7 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 	unsigned i = 0;
 	bool bounce = false;
 	int sectors = 0;
+	bool passthrough = bio_is_passthrough(*bio_orig);
 
 	bio_for_each_segment(from, *bio_orig, iter) {
 		if (i++ < BIO_MAX_PAGES)
@@ -209,13 +210,14 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 	if (!bounce)
 		return;
 
-	if (sectors < bio_sectors(*bio_orig)) {
+	if (!passthrough && sectors < bio_sectors(*bio_orig)) {
 		bio = bio_split(*bio_orig, sectors, GFP_NOIO, bounce_bio_split);
 		bio_chain(bio, *bio_orig);
 		generic_make_request(*bio_orig);
 		*bio_orig = bio;
 	}
-	bio = bio_clone_bioset(*bio_orig, GFP_NOIO, bounce_bio_set);
+	bio = bio_clone_bioset(*bio_orig, GFP_NOIO, passthrough ? NULL :
+			bounce_bio_set);
 
 	bio_for_each_segment_all(to, bio, i) {
 		struct page *page = to->bv_page;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index bed098696f0d..6e8da5655095 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -240,14 +240,24 @@ struct request {
 	struct request *next_rq;
 };
 
+static inline bool blk_op_is_scsi(unsigned int op)
+{
+	return op == REQ_OP_SCSI_IN || op == REQ_OP_SCSI_OUT;
+}
+
+static inline bool blk_op_is_private(unsigned int op)
+{
+	return op == REQ_OP_DRV_IN || op == REQ_OP_DRV_OUT;
+}
+
 static inline bool blk_rq_is_scsi(struct request *rq)
 {
-	return req_op(rq) == REQ_OP_SCSI_IN || req_op(rq) == REQ_OP_SCSI_OUT;
+	return blk_op_is_scsi(req_op(rq));
 }
 
 static inline bool blk_rq_is_private(struct request *rq)
 {
-	return req_op(rq) == REQ_OP_DRV_IN || req_op(rq) == REQ_OP_DRV_OUT;
+	return blk_op_is_private(req_op(rq));
 }
 
 static inline bool blk_rq_is_passthrough(struct request *rq)
@@ -255,6 +265,13 @@ static inline bool blk_rq_is_passthrough(struct request *rq)
 	return blk_rq_is_scsi(rq) || blk_rq_is_private(rq);
 }
 
+static inline bool bio_is_passthrough(struct bio *bio)
+{
+	unsigned op = bio_op(bio);
+
+	return blk_op_is_scsi(op) || blk_op_is_private(op);
+}
+
 static inline unsigned short req_get_ioprio(struct request *req)
 {
 	return req->ioprio;
-- 
2.12.3