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Commit 423f04d6 authored by NeilBrown's avatar NeilBrown
Browse files

md/raid1: extend spinlock to protect raid1_end_read_request against inconsistencies 



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: 34cab6f4 ("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: 76073054 ("md/raid1: clean up read_balance.")
Cc: stable@vger.kernel.org (v3.0+)
Signed-off-by: default avatarNeilBrown <neilb@suse.com>
parent 74d33293

drivers/md/raid1.c

+6 −4
Original line number Diff line number Diff line
@@ -1476,6 +1476,7 @@ static void error(struct mddev *mddev, struct md_rdev *rdev) 
{

	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
@@ -1495,14 +1496,13 @@ static void error(struct mddev *mddev, struct md_rdev *rdev) 
		return;

	}

	set_bit(Blocked, &rdev->flags);

	if (test_and_clear_bit(In_sync, &rdev->flags)) {

		unsigned long flags;

	spin_lock_irqsave(&conf->device_lock, flags);

	if (test_and_clear_bit(In_sync, &rdev->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.

	 */
@@ -1568,7 +1568,10 @@ static int raid1_spare_active(struct mddev *mddev) 
	 * 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 mddev *mddev) 
			sysfs_notify_dirent_safe(rdev->sysfs_state);

		}

	}

	spin_lock_irqsave(&conf->device_lock, flags);

	mddev->degraded -= count;

	spin_unlock_irqrestore(&conf->device_lock, flags);