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

[Ming Lei]

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 <s...@kernel.org>
Cc: linux-r...@vger.kernel.org
Signed-off-by: Ming Lei <ming....@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