linux-kernel - [PATCH v2 12/51] md: raid10: avoid to access bvec table directly

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Date:   Mon, 26 Jun 2017 20:09:55 +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>, Shaohua Li <shli@...nel.org>,
        linux-raid@...r.kernel.org
Subject: [PATCH v2 12/51] md: raid10: avoid to access bvec table directly

Inside sync_request_write(), .bi_vcnt is written after this bio
is reseted, this way won't work any more after multipage bvec
is enabled.

So reset_bvec_table() is introduced for re-add these pages into
bio, then .bi_vcnt needn't to be touched any more.

Cc: Shaohua Li <shli@...nel.org>
Cc: linux-raid@...r.kernel.org
Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 drivers/md/raid10.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 5026e7ad51d3..2fca1fe67092 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1995,6 +1995,24 @@ static void end_sync_write(struct bio *bio)
 	end_sync_request(r10_bio);
 }
 
+/* called after bio_reset() */
+static void reset_bvec_table(struct bio *bio, struct resync_pages *rp, int size)
+{
+	/* initialize bvec table again */
+	rp->idx = 0;
+	do {
+		struct page *page = resync_fetch_page(rp, rp->idx++);
+		int len = min_t(int, size, PAGE_SIZE);
+
+		/*
+		 * won't fail because the vec table is big
+		 * enough to hold all these pages
+		 */
+		bio_add_page(bio, page, len, 0);
+		size -= len;
+	} while (rp->idx < RESYNC_PAGES && size > 0);
+}
+
 /*
  * Note: sync and recover and handled very differently for raid10
  * This code is for resync.
@@ -2087,8 +2105,8 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
 		rp = get_resync_pages(tbio);
 		bio_reset(tbio);
 
-		tbio->bi_vcnt = vcnt;
-		tbio->bi_iter.bi_size = fbio->bi_iter.bi_size;
+		reset_bvec_table(tbio, rp, fbio->bi_iter.bi_size);
+
 		rp->raid_bio = r10_bio;
 		tbio->bi_private = rp;
 		tbio->bi_iter.bi_sector = r10_bio->devs[i].addr;
-- 
2.9.4