md/raid5: In ops_run_io, inc nr_pending before calling md_wait_for_blocked_rdev

In ops_run_io(), the call to md_wait_for_blocked_rdev will decrement
nr_pending so we lose the reference we hold on the rdev.
So atomic_inc it first to maintain the reference.

This bug was introduced by commit  73e92e51b7969ef5477d
    md/raid5.  Don't write to known bad block on doubtful devices.

which appeared in 3.0, so patch is suitable for stable kernels since
then.

Cc: stable@vger.kernel.org
Signed-off-by: majianpeng <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 9567a9c83a1f..befadb41a11f 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -606,6 +606,12 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
                                          * a chance*/
                                         md_check_recovery(conf->mddev);
                                 }
+                                /*
+                                 * Because md_wait_for_blocked_rdev
+                                 * will dec nr_pending, we must
+                                 * increment it first.
+                                 */
+                                atomic_inc(&rdev->nr_pending);
                                 md_wait_for_blocked_rdev(rdev, conf->mddev);
                         } else {
                                 /* Acknowledged bad block - skip the write */