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SubjectRe: FW: [PATCH 008 of 9] md: Fix possible raid1/raid10 deadlock on read error during resync.

>
> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org
> [mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of NeilBrown
> Sent: Sunday, March 02, 2008 5:18 PM
> To: Andrew Morton
> Cc: linux-raid@vger.kernel.org; linux-kernel@vger.kernel.org; K.Tanaka
> Subject: [PATCH 008 of 9] md: Fix possible raid1/raid10 deadlock on read
> error during resync.
>

> diff .prev/drivers/md/raid1.c ./drivers/md/raid1.c
> --- .prev/drivers/md/raid1.c 2008-03-03 11:03:39.000000000 +1100
> +++ ./drivers/md/raid1.c 2008-03-03 09:56:52.000000000 +1100
> @@ -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); }));
> --

When we call freeze_array, it is after reschedule_retry, during which conf->nr_queued is already incremented.
Should we use conf->nr_pending == conf->nr_pending here?




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