The patch titled
md: fix possible raid1/raid10 deadlock on read error during resync
has been added to the -mm tree. Its filename is
md-fix-possible-raid1-raid10-deadlock-on-read-error-during-resync.patch
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------------------------------------------------------
Subject: md: fix possible raid1/raid10 deadlock on read error during resync
From: NeilBrown <neilb@xxxxxxx>
Thanks to K.Tanaka and the scsi fault injection framework, here is a fix for
another possible deadlock in raid1/raid10 error handing.
If a read request returns an error while a resync is happening and a resync
request is pending, the attempt to fix the error will block until the resync
progresses, and the resync will block until the read request completes. Thus
a deadlock.
This patch fixes the problem.
Cc: "K.Tanaka" <k-tanaka@xxxxxxxxxxxxx>
Signed-off-by: Neil Brown <neilb@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/md/raid1.c | 11 +++++++++--
drivers/md/raid10.c | 11 +++++++++--
2 files changed, 18 insertions(+), 4 deletions(-)
diff -puN drivers/md/raid1.c~md-fix-possible-raid1-raid10-deadlock-on-read-error-during-resync drivers/md/raid1.c
--- a/drivers/md/raid1.c~md-fix-possible-raid1-raid10-deadlock-on-read-error-during-resync
+++ a/drivers/md/raid1.c
@@ -704,13 +704,20 @@ static void freeze_array(conf_t *conf)
/* stop syncio and normal IO and wait for everything to
* go quite.
* We increment barrier and nr_waiting, and then
- * wait until barrier+nr_pending match nr_queued+2
+ * wait until nr_pending match nr_queued+1
+ * This is called in the context of one normal IO request
+ * that has failed. Thus any sync request that might be pending
+ * will be blocked by nr_pending, and we need to wait for
+ * pending IO requests to complete or be queued for re-try.
+ * Thus the number queued (nr_queued) plus this request (1)
+ * must match the number of pending IOs (nr_pending) before
+ * we continue.
*/
spin_lock_irq(&conf->resync_lock);
conf->barrier++;
conf->nr_waiting++;
wait_event_lock_irq(conf->wait_barrier,
- conf->barrier+conf->nr_pending == conf->nr_queued+2,
+ conf->nr_pending == conf->nr_queued+1,
conf->resync_lock,
({ flush_pending_writes(conf);
raid1_unplug(conf->mddev->queue); }));
diff -puN drivers/md/raid10.c~md-fix-possible-raid1-raid10-deadlock-on-read-error-during-resync drivers/md/raid10.c
--- a/drivers/md/raid10.c~md-fix-possible-raid1-raid10-deadlock-on-read-error-during-resync
+++ a/drivers/md/raid10.c
@@ -747,13 +747,20 @@ static void freeze_array(conf_t *conf)
/* stop syncio and normal IO and wait for everything to
* go quiet.
* We increment barrier and nr_waiting, and then
- * wait until barrier+nr_pending match nr_queued+2
+ * wait until nr_pending match nr_queued+1
+ * This is called in the context of one normal IO request
+ * that has failed. Thus any sync request that might be pending
+ * will be blocked by nr_pending, and we need to wait for
+ * pending IO requests to complete or be queued for re-try.
+ * Thus the number queued (nr_queued) plus this request (1)
+ * must match the number of pending IOs (nr_pending) before
+ * we continue.
*/
spin_lock_irq(&conf->resync_lock);
conf->barrier++;
conf->nr_waiting++;
wait_event_lock_irq(conf->wait_barrier,
- conf->barrier+conf->nr_pending == conf->nr_queued+2,
+ conf->nr_pending == conf->nr_queued+1,
conf->resync_lock,
({ flush_pending_writes(conf);
raid10_unplug(conf->mddev->queue); }));
_
Patches currently in -mm which might be from neilb@xxxxxxx are
git-nfsd.patch
md-fix-deadlock-in-md-raid1-and-md-raid10-when-handling-a-read-error.patch
md-reduce-cpu-wastage-on-idle-md-array-with-a-write-intent-bitmap.patch
md-guard-against-possible-bad-array-geometry-in-v1-metadata.patch
md-clean-up-irregularity-with-raid-autodetect.patch
md-make-sure-a-reshape-is-started-when-device-switches-to-read-write.patch
md-lock-access-to-rdev-attributes-properly.patch
md-dont-attempt-read-balancing-for-raid10-far-layouts.patch
md-fix-possible-raid1-raid10-deadlock-on-read-error-during-resync.patch
md-the-md-raid10-resync-thread-could-cause-a-md-raid10-array-deadlock.patch
md-fix-integer-as-null-pointer-warnings-in-mdc.patch
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