linux-kernel - [PATCH 4.4 48/50] block: dont optimize for non-cloned bio in bio_get_last

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Message-Id: <20160314175020.196951340@linuxfoundation.org>
Date:	Mon, 14 Mar 2016 10:51:06 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Kent Overstreet <kent.overstreet@...il.com>,
	Ming Lei <ming.lei@...onical.com>, Jens Axboe <axboe@...com>
Subject: [PATCH 4.4 48/50] block: dont optimize for non-cloned bio in bio_get_last_bvec()

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

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

From: Ming Lei <ming.lei@...onical.com>

commit 90d0f0f11588ec692c12f9009089b398be395184 upstream.

For !BIO_CLONED bio, we can use .bi_vcnt safely, but it
doesn't mean we can just simply return .bi_io_vec[.bi_vcnt - 1]
because the start postion may have been moved in the middle of
the bvec, such as splitting in the middle of bvec.

Fixes: 7bcd79ac50d9(block: bio: introduce helpers to get the 1st and last bvec)
Reported-by: Kent Overstreet <kent.overstreet@...il.com>
Signed-off-by: Ming Lei <ming.lei@...onical.com>
Signed-off-by: Jens Axboe <axboe@...com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 include/linux/bio.h |    5 -----
 1 file changed, 5 deletions(-)

--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -320,11 +320,6 @@ static inline void bio_get_last_bvec(str
 	struct bvec_iter iter = bio->bi_iter;
 	int idx;
 
-	if (!bio_flagged(bio, BIO_CLONED)) {
-		*bv = bio->bi_io_vec[bio->bi_vcnt - 1];
-		return;
-	}
-
 	if (unlikely(!bio_multiple_segments(bio))) {
 		*bv = bio_iovec(bio);
 		return;