linux-kernel - [PATCH 4.3 014/200] block: ensure to split after potentially bouncing a bio

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Date:	Sun, 14 Feb 2016 14:20:21 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, "Artem S. Tashkinov" <t.artem@...os.com>,
	Jens Axboe <axboe@...com>
Subject: [PATCH 4.3 014/200] block: ensure to split after potentially bouncing a bio

4.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Junichi Nomura <j-nomura@...jp.nec.com>

commit 23688bf4f830a89866fd0ed3501e342a7360fe4f upstream.

blk_queue_bio() does split then bounce, which makes the segment
counting based on pages before bouncing and could go wrong. Move
the split to after bouncing, like we do for blk-mq, and the we
fix the issue of having the bio count for segments be wrong.

Fixes: 54efd50bfd87 ("block: make generic_make_request handle arbitrarily sized bios")
Tested-by: Artem S. Tashkinov <t.artem@...os.com>
Signed-off-by: Jens Axboe <axboe@...com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 block/blk-core.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1616,8 +1616,6 @@ static void blk_queue_bio(struct request
 	struct request *req;
 	unsigned int request_count = 0;

-	blk_queue_split(q, &bio, q->bio_split);
-
 	/*
 	 * low level driver can indicate that it wants pages above a
 	 * certain limit bounced to low memory (ie for highmem, or even
@@ -1625,6 +1623,8 @@ static void blk_queue_bio(struct request
 	 */
 	blk_queue_bounce(q, &bio);

+	blk_queue_split(q, &bio, q->bio_split);
+
 	if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
 		bio->bi_error = -EIO;
 		bio_endio(bio);