linux-kernel - [PATCH] block: fix bio splitting on max sectors

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <1453487372-8391-1-git-send-email-tom.leiming@gmail.com>
Date:	Sat, 23 Jan 2016 02:29:32 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Cc:	linux-block@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Stefan Haberland <sth@...ux.vnet.ibm.com>,
	Keith Busch <keith.busch@...el.com>,
	Ming Lei <tom.leiming@...il.com>
Subject: [PATCH] block: fix bio splitting on max sectors

After commit e36f62042880(block: split bios to maxpossible length),
bio can be splitted in the middle of a vector entry, then it
is easy to split out one bio which size isn't aligned with block
size, especially when the block size is bigger than 512.

This patch fixes the issue by making the max io size aligned
to logical block size.

Fixes: e36f62042880(block: split bios to maxpossible length)
Reported-by: Stefan Haberland <sth@...ux.vnet.ibm.com>
Cc: Keith Busch <keith.busch@...el.com>
Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ming Lei <tom.leiming@...il.com>
---
 block/blk-merge.c | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 1699df5..ad22153 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -70,6 +70,18 @@ static struct bio *blk_bio_write_same_split(struct request_queue *q,
 	return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
 }
 
+static inline unsigned get_max_io_size(struct request_queue *q,
+				       struct bio *bio)
+{
+	unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
+	unsigned mask = ~(queue_logical_block_size(q) - 1);
+
+	/* aligned to logical block size */
+	sectors = ((sectors << 9) & mask) >> 9;
+
+	return sectors;
+}
+
 static struct bio *blk_bio_segment_split(struct request_queue *q,
 					 struct bio *bio,
 					 struct bio_set *bs,
@@ -81,6 +93,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
 	unsigned front_seg_size = bio->bi_seg_front_size;
 	bool do_split = true;
 	struct bio *new = NULL;
+	unsigned max_sectors;
 
 	bio_for_each_segment(bv, bio, iter) {
 		/*
@@ -90,20 +103,20 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
 		if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
 			goto split;
 
-		if (sectors + (bv.bv_len >> 9) >
-				blk_max_size_offset(q, bio->bi_iter.bi_sector)) {
+		max_sectors = get_max_io_size(q, bio);
+		if (sectors + (bv.bv_len >> 9) > max_sectors) {
 			/*
 			 * Consider this a new segment if we're splitting in
 			 * the middle of this vector.
 			 */
 			if (nsegs < queue_max_segments(q) &&
-			    sectors < blk_max_size_offset(q,
-						bio->bi_iter.bi_sector)) {
+			    sectors < max_sectors) {
 				nsegs++;
-				sectors = blk_max_size_offset(q,
-						bio->bi_iter.bi_sector);
+				sectors = max_sectors;
 			}
-			goto split;
+			if (sectors)
+				goto split;
+			/* Make this single bvec as the 1st segment */
 		}
 
 		if (bvprvp && blk_queue_cluster(q)) {
-- 
1.9.1