linux-kernel - [ 16/48] md/raid5: In ops_run_io, inc nr_pending before calling md_wait_for_blocked

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Message-Id: <20120709143119.018962208@decadent.org.uk>
Date:	Mon, 09 Jul 2012 15:31:32 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, majianpeng <majianpeng@...il.com>,
	NeilBrown <neilb@...e.de>
Subject: [ 16/48] md/raid5: In ops_run_io, inc nr_pending before calling
 md_wait_for_blocked_rdev

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: majianpeng <majianpeng@...il.com>

commit 1850753d2e6d9ca7856581ca5d3cf09521e6a5d7 upstream.

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.

Signed-off-by: majianpeng <majianpeng@...il.com>
Signed-off-by: NeilBrown <neilb@...e.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/md/raid5.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 9567a9c..befadb4 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 */


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