diff options
| author | Takahiro Yasui <tyasui@redhat.com> | 2010-03-06 02:32:35 +0000 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2010-03-06 02:32:35 +0000 |
| commit | f070304094edb8d516423e79edd27c97ec2020b0 (patch) | |
| tree | 0330115839e84c4b5db8e2318a932f2dee78eba4 /drivers/md | |
| parent | 924e600d417ead9ef67043988055ba236f114718 (diff) | |
| download | lwn-f070304094edb8d516423e79edd27c97ec2020b0.tar.gz lwn-f070304094edb8d516423e79edd27c97ec2020b0.zip | |
dm raid1: fix deadlock when suspending failed device
To prevent deadlock, bios in the hold list should be flushed before
dm_rh_stop_recovery() is called in mirror_suspend().
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.
Signed-off-by: Takahiro Yasui <tyasui@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/dm-raid1.c | 41 |
1 files changed, 23 insertions, 18 deletions
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c index 6d66ddf39071..ddda531723dc 100644 --- a/drivers/md/dm-raid1.c +++ b/drivers/md/dm-raid1.c @@ -465,9 +465,17 @@ static void map_region(struct dm_io_region *io, struct mirror *m, 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 *ms, struct bio *bio) /* * Hold bio until the suspend is complete. */ - spin_lock_irq(&ms->lock); bio_list_add(&ms->holds, bio); spin_unlock_irq(&ms->lock); } @@ -1261,6 +1268,20 @@ static void mirror_presuspend(struct dm_target *ti) 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). */ @@ -1280,22 +1301,6 @@ static void mirror_presuspend(struct dm_target *ti) * 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) |