linux-kernel - [PATCH v2 05/51] fs/buffer: comment on direct access to bvec table

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Message-Id: <20170626121034.3051-6-ming.lei@redhat.com>
Date:   Mon, 26 Jun 2017 20:09:48 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Jens Axboe <axboe@...com>, Christoph Hellwig <hch@...radead.org>,
        Huang Ying <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        Ming Lei <ming.lei@...hat.com>
Subject: [PATCH v2 05/51] fs/buffer: comment on direct access to bvec table

Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 fs/buffer.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 4d5d03b42e11..1910f539770b 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3052,8 +3052,13 @@ static void end_bio_bh_io_sync(struct bio *bio)
 void guard_bio_eod(int op, struct bio *bio)
 {
 	sector_t maxsector;
-	struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
 	unsigned truncated_bytes;
+	/*
+	 * It is safe to truncate the last bvec in the following way
+	 * even though multipage bvec is supported, but we need to
+	 * fix the parameters passed to zero_user().
+	 */
+	struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
 
 	maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
 	if (!maxsector)
-- 
2.9.4