linux-kernel - [PATCH] block: return the correct first bvec when checking for gaps

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Message-Id: <1622746005-10785-1-git-send-email-longli@linuxonhyperv.com>
Date:   Thu,  3 Jun 2021 11:46:45 -0700
From:   longli@...uxonhyperv.com
To:     linux-block@...r.kernel.org
Cc:     Long Li <longli@...rosoft.com>, Jens Axboe <axboe@...nel.dk>,
        Johannes Thumshirn <johannes.thumshirn@....com>,
        Pavel Begunkov <asml.silence@...il.com>,
        Ming Lei <ming.lei@...hat.com>, Tejun Heo <tj@...nel.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Jeffle Xu <jefflexu@...ux.alibaba.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH] block: return the correct first bvec when checking for gaps

From: Long Li <longli@...rosoft.com>

After commit 07173c3ec276 ("block: enable multipage bvecs"), a bvec can
have multiple pages. But bio_will_gap() still assumes one page bvec while
checking for merging. This causes data corruption on drivers relying on
the correct merging on virt_boundary_mask.

Fix this by returning the bvec for multi-page bvec.

Cc: Jens Axboe <axboe@...nel.dk>
Cc: Johannes Thumshirn <johannes.thumshirn@....com>
Cc: Pavel Begunkov <asml.silence@...il.com>
Cc: Ming Lei <ming.lei@...hat.com>
Cc: Tejun Heo <tj@...nel.org>
Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc: Jeffle Xu <jefflexu@...ux.alibaba.com>
Cc: linux-kernel@...r.kernel.org
Cc: stable@...r.kernel.org
Fixes: 07173c3ec276 ("block: enable multipage bvecs")
Signed-off-by: Long Li <longli@...rosoft.com>
---
 include/linux/bio.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index a0b4cfdf62a4..e89242a53bbc 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -271,7 +271,7 @@ static inline void bio_clear_flag(struct bio *bio, unsigned int bit)
 
 static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
 {
-	*bv = bio_iovec(bio);
+	*bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
 }
 
 static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv)
-- 
2.17.1