linux-kernel - [ 073/218] md/raid5: fix calculate of degraded when a replacement becomes active.

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Message-Id: <20120928201509.969336506@linuxfoundation.org>
Date:	Fri, 28 Sep 2012 13:14:50 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, Robin Hill <robin@...inhill.me.uk>,
	John Drescher <drescherjm@...il.com>, NeilBrown <neilb@...e.de>
Subject: [ 073/218] md/raid5: fix calculate of degraded when a replacement becomes active.

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

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

From: NeilBrown <neilb@...e.de>

commit e5c86471f933608db5d43679f84cb4346c32033e upstream.

When a replacement device becomes active, we mark the device that it
replaces as 'faulty' so that it can subsequently get removed.
However 'calc_degraded' only pays attention to the primary device, not
the replacement, so the array appears to become degraded, which is
wrong.

So teach 'calc_degraded' to consider any replacement if a primary
device is faulty.

This is suitable for -stable as an incorrect 'degraded' value can
confuse md and could lead to data corruption.
This is only relevant for 3.3 and later.

Reported-by: Robin Hill <robin@...inhill.me.uk>
Reported-by: John Drescher <drescherjm@...il.com>
Signed-off-by: NeilBrown <neilb@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/raid5.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -380,6 +380,8 @@ static int calc_degraded(struct r5conf *
 	degraded = 0;
 	for (i = 0; i < conf->previous_raid_disks; i++) {
 		struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);
+		if (rdev && test_bit(Faulty, &rdev->flags))
+			rdev = rcu_dereference(conf->disks[i].replacement);
 		if (!rdev || test_bit(Faulty, &rdev->flags))
 			degraded++;
 		else if (test_bit(In_sync, &rdev->flags))
@@ -404,6 +406,8 @@ static int calc_degraded(struct r5conf *
 	degraded2 = 0;
 	for (i = 0; i < conf->raid_disks; i++) {
 		struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);
+		if (rdev && test_bit(Faulty, &rdev->flags))
+			rdev = rcu_dereference(conf->disks[i].replacement);
 		if (!rdev || test_bit(Faulty, &rdev->flags))
 			degraded2++;
 		else if (test_bit(In_sync, &rdev->flags))


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