md/raid10: call wait_barrier() for each request submitted.

wait_barrier() includes a counter, so we must call it precisely once
(unless balanced by allow_barrier()) for each request submitted.

Since
commit 20d0189b1012a37d2533a87fb451f7852f2418d1
    block: Introduce new bio_split()
in 3.14-rc1, we don't call it for the extra requests generated when
we need to split a bio.

When this happens the counter goes negative, any resync/recovery will
never start, and  "mdadm --stop" will hang.

Reported-by: Chris Murphy <lists@colorremedies.com>
Fixes: 20d0189b1012a37d2533a87fb451f7852f2418d1
Cc: stable@vger.kernel.org (3.14+)
Cc: Kent Overstreet <kmo@daterainc.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 7 insertions, 6 deletions

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 33fc408e5eac..cb882aae9e20 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1172,6 +1172,13 @@ static void __make_request(struct mddev *mddev, struct bio *bio)
         int max_sectors;
         int sectors;
 
+        /*
+         * Register the new request and wait if the reconstruction
+         * thread has put up a bar for new requests.
+         * Continue immediately if no resync is active currently.
+         */
+        wait_barrier(conf);
+
         sectors = bio_sectors(bio);
         while (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
             bio->bi_iter.bi_sector < conf->reshape_progress &&
@@ -1552,12 +1559,6 @@ static void make_request(struct mddev *mddev, struct bio *bio)
 
         md_write_start(mddev, bio);
 
-        /*
-         * Register the new request and wait if the reconstruction
-         * thread has put up a bar for new requests.
-         * Continue immediately if no resync is active currently.
-         */
-        wait_barrier(conf);
 
         do {