linux-kernel - [PATCH v2 31/51] fs/buffer.c: use bvec iterator to truncate the bio

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Date:   Mon, 26 Jun 2017 20:10:14 +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 31/51] fs/buffer.c: use bvec iterator to truncate the bio

Once multipage bvec is enabled, the last bvec may include
more than one page, this patch use bvec_get_last_page()
to truncate the bio.

Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 fs/buffer.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 1910f539770b..53b8a29f4525 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3055,8 +3055,7 @@ void guard_bio_eod(int op, struct bio *bio)
 	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().
+	 * even though multipage bvec is supported.
 	 */
 	struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
 
@@ -3085,7 +3084,10 @@ void guard_bio_eod(int op, struct bio *bio)
 
 	/* ..and clear the end of the buffer for reads */
 	if (op == REQ_OP_READ) {
-		zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len,
+		struct bio_vec bv;
+
+		bvec_get_last_page(bvec, &bv);
+		zero_user(bv.bv_page, bv.bv_offset + bv.bv_len,
 				truncated_bytes);
 	}
 }
-- 
2.9.4