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Patch "md/raid1: extend spinlock to protect raid1_end_read_request against inconsistencies" has been added to the 3.14-stable tree

PATCH [email protected] 1 participant 1 message Aug 14, 2015

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This is a note to let you know that I've just added the patch titled

md/raid1: extend spinlock to protect raid1_end_read_request against inconsistencies

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
md-raid1-extend-spinlock-to-protect-raid1_end_read_request-against-inconsistencies.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 423f04d63cf421ea436bcc5be02543d549ce4b28 Mon Sep 17 00:00:00 2001

From: NeilBrown <[email protected]>
Date: Mon, 27 Jul 2015 11:48:52 +1000
Subject: md/raid1: extend spinlock to protect raid1_end_read_request against inconsistencies

From: NeilBrown <[email protected]>

commit 423f04d63cf421ea436bcc5be02543d549ce4b28 upstream.

raid1_end_read_request() assumes that the In_sync bits are consistent with the ->degaded count.
raid1_spare_active updates the In_sync bit before the ->degraded count and so exposes an inconsistency, as does error()
So extend the spinlock in raid1_spare_active() and error() to hide those inconsistencies.

This should probably be part of
Commit: 34cab6f42003 ("md/raid1: fix test for 'was read error from last working device'.")
as it addresses the same issue. It fixes the same bug and should go to -stable for same reasons.

Fixes 76073054c95b ("md/raid1: clean up read_balance.")
Signed-off-by NeilBrown <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/md/raid1.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)
drivers/md/raid1.c +6 -4
@@ -1477,6 +1477,7 @@ static void error(struct mddev *mddev, s
 {
 	char b[BDEVNAME_SIZE];
 	struct r1conf *conf = mddev->private;
+	unsigned long flags;
 
 	/*
 	 * If it is not operational, then we have already marked it as dead

@@ -1496,14 +1497,13 @@ static void error(struct mddev *mddev, s
 		return;
 	}
 	set_bit(Blocked, &rdev->flags);
+	spin_lock_irqsave(&conf->device_lock, flags);
 	if (test_and_clear_bit(In_sync, &rdev->flags)) {
-		unsigned long flags;
-		spin_lock_irqsave(&conf->device_lock, flags);
 		mddev->degraded++;
 		set_bit(Faulty, &rdev->flags);
-		spin_unlock_irqrestore(&conf->device_lock, flags);
 	} else
 		set_bit(Faulty, &rdev->flags);
+	spin_unlock_irqrestore(&conf->device_lock, flags);
 	/*
 	 * if recovery is running, make sure it aborts.
 	 */

@@ -1569,7 +1569,10 @@ static int raid1_spare_active(struct mdd
 	 * Find all failed disks within the RAID1 configuration 
 	 * and mark them readable.
 	 * Called under mddev lock, so rcu protection not needed.
+	 * device_lock used to avoid races with raid1_end_read_request
+	 * which expects 'In_sync' flags and ->degraded to be consistent.
 	 */
+	spin_lock_irqsave(&conf->device_lock, flags);
 	for (i = 0; i < conf->raid_disks; i++) {
 		struct md_rdev *rdev = conf->mirrors[i].rdev;
 		struct md_rdev *repl = conf->mirrors[conf->raid_disks + i].rdev;

@@ -1599,7 +1602,6 @@ static int raid1_spare_active(struct mdd
 			sysfs_notify_dirent_safe(rdev->sysfs_state);
 		}
 	}
-	spin_lock_irqsave(&conf->device_lock, flags);
 	mddev->degraded -= count;
 	spin_unlock_irqrestore(&conf->device_lock, flags);

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/md-raid1-extend-spinlock-to-protect-raid1_end_read_request-against-inconsistencies.patch queue-3.14/md-use-kzalloc-when-bitmap-is-disabled.patch