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

Ming Lei
2017-06-26T12:09:55Z

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@kernel.org>
Cc: linux-raid@vger.kernel.org
Signed-off-by: Ming Lei <ming.lei@redhat.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