Re: BUG - raid 1 deadlock on handle_read_error / wait_barrier

[NeilBrown <neilb@suse.de>]

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On Sat, 8 Jun 2013 12:45:41 +0300 Alexander Lyakas <alex.bolshoy@gmail.com>
wrote:

> Hi Neil,
> after reading the code of raid1.c, I see that there's also
> conf->retry_list, which is also flushed by raid1d, but not by
> flush_pending_writes(). So I think it can also cause similar deadlock,
> but I don't know how to fix it:(
> 

Good point.
Requests in retry_list are counted in nr_queued, which is checked in
freeze_array().

And freeze_array() already calls flush_pending_writes().

So I suspect the right thing to do is use freeze_array() in place of
raise_barrier().

So maybe this is the right approach.

Testing greatly appreciated...

Thanks,
NeilBrown



diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 226dcd0..240b328 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1569,8 +1569,8 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
 		 * we wait for all outstanding requests to complete.
 		 */
 		synchronize_sched();
-		raise_barrier(conf);
-		lower_barrier(conf);
+		freeze_array(conf);
+		unfreeze_array(conf);
 		clear_bit(Unmerged, &rdev->flags);
 	}
 	md_integrity_add_rdev(rdev, mddev);
@@ -1620,11 +1620,11 @@ static int raid1_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
 			 */
 			struct md_rdev *repl =
 				conf->mirrors[conf->raid_disks + number].rdev;
-			raise_barrier(conf);
+			freeze_array(conf);
 			clear_bit(Replacement, &repl->flags);
 			p->rdev = repl;
 			conf->mirrors[conf->raid_disks + number].rdev = NULL;
-			lower_barrier(conf);
+			unfreeze_array(conf);
 			clear_bit(WantReplacement, &rdev->flags);
 		} else
 			clear_bit(WantReplacement, &rdev->flags);
@@ -3021,7 +3021,7 @@ static int raid1_reshape(struct mddev *mddev)
 		return -ENOMEM;
 	}
 
-	raise_barrier(conf);
+	freeze_array(conf);
 
 	/* ok, everything is stopped */
 	oldpool = conf->r1bio_pool;
@@ -3052,7 +3052,7 @@ static int raid1_reshape(struct mddev *mddev)
 	conf->raid_disks = mddev->raid_disks = raid_disks;
 	mddev->delta_disks = 0;
 
-	lower_barrier(conf);
+	unfreeze_array(conf);
 
 	set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
 	md_wakeup_thread(mddev->thread);

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