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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 02-17-2010, 10:43 PM
Mikulas Patocka
 
Default dm-raid1: fix deadlock at suspending failed device

On Wed, 17 Feb 2010, Takahiro Yasui wrote:

> This is a repost of the following patch but its description is revised.
>
> 1/8/2010 3:08 PM
> [PATCH][BUGFIX] dm-raid1: fix suspend stuck of failed device
>
> I appreciate your review.
>
> Thanks,
> Taka

Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>

Mikulas

> The recovery can't start because there are pending bios and therefore
> dm_rh_stop_recovery deadlocks.
>
> When there are pending bios in the hold list, the recovery waits for
> the completion of the bios after recovery_count is acquired.
> The recovery_count is released when the recovery finished, however,
> the bios in the hold list are processed after dm_rh_stop_recovery() in
> mirror_presuspend(). dm_rh_stop_recovery() also acquires recovery_count,
> then deadlock occurs.
>
> To prevent deadlock, bios in the hold list should be flushed before
> dm_rh_stop_recovery() is called in mirror_suspend().
>
>
> Signed-off-by: Takahiro Yasui <tyasui@redhat.com>
> ---
> drivers/md/dm-raid1.c | 41 +++++++++++++++++++++++------------------
> 1 file changed, 23 insertions(+), 18 deletions(-)
>
> Index: linux-2.6.33-rc1/drivers/md/dm-raid1.c
> ================================================== =================
> --- linux-2.6.33-rc1.orig/drivers/md/dm-raid1.c
> +++ linux-2.6.33-rc1/drivers/md/dm-raid1.c
> @@ -465,9 +465,17 @@ static void map_region(struct dm_io_regi
> static void hold_bio(struct mirror_set *ms, struct bio *bio)
> {
> /*
> - * If device is suspended, complete the bio.
> + * Lock is required to avoid race condition during suspend
> + * process.
> */
> + spin_lock_irq(&ms->lock);
> +
> if (atomic_read(&ms->suspend)) {
> + spin_unlock_irq(&ms->lock);
> +
> + /*
> + * If device is suspended, complete the bio.
> + */
> if (dm_noflush_suspending(ms->ti))
> bio_endio(bio, DM_ENDIO_REQUEUE);
> else
> @@ -478,7 +486,6 @@ static void hold_bio(struct mirror_set *
> /*
> * Hold bio until the suspend is complete.
> */
> - spin_lock_irq(&ms->lock);
> bio_list_add(&ms->holds, bio);
> spin_unlock_irq(&ms->lock);
> }
> @@ -1259,6 +1266,20 @@ static void mirror_presuspend(struct dm_
> atomic_set(&ms->suspend, 1);
>
> /*
> + * Process bios in the hold list to start recovery waiting
> + * for bios in the hold list. After the process, no bio has
> + * a chance to be added in the hold list because ms->suspend
> + * is set.
> + */
> + spin_lock_irq(&ms->lock);
> + holds = ms->holds;
> + bio_list_init(&ms->holds);
> + spin_unlock_irq(&ms->lock);
> +
> + while ((bio = bio_list_pop(&holds)))
> + hold_bio(ms, bio);
> +
> + /*
> * We must finish up all the work that we've
> * generated (i.e. recovery work).
> */
> @@ -1278,22 +1299,6 @@ static void mirror_presuspend(struct dm_
> * we know that all of our I/O has been pushed.
> */
> flush_workqueue(ms->kmirrord_wq);
> -
> - /*
> - * Now set ms->suspend is set and the workqueue flushed, no more
> - * entries can be added to ms->hold list, so process it.
> - *
> - * Bios can still arrive concurrently with or after this
> - * presuspend function, but they cannot join the hold list
> - * because ms->suspend is set.
> - */
> - spin_lock_irq(&ms->lock);
> - holds = ms->holds;
> - bio_list_init(&ms->holds);
> - spin_unlock_irq(&ms->lock);
> -
> - while ((bio = bio_list_pop(&holds)))
> - hold_bio(ms, bio);
> }
>
> static void mirror_postsuspend(struct dm_target *ti)
>

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