4.2.8-ckt7 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------ From: Shaohua Li <[email protected]> commit 6ab2a4b806ae21b6c3e47c5ff1285ec06d505325 upstream. Revert commit e9e4c377e2f563(md/raid5: per hash value and exclusive wait_for_stripe) The problem is raid5_get_active_stripe waits on conf->wait_for_stripe[hash]. Assume hash is 0. My test release stripes in this order: - release all stripes with hash 0 - raid5_get_active_stripe still sleeps since active_stripes > max_nr_stripes * 3 / 4 - release all stripes with hash other than 0. active_stripes becomes 0 - raid5_get_active_stripe still sleeps, since nobody wakes up wait_for_stripe[0] The system live locks. The problem is active_stripes isn't a per-hash count. Revert the patch makes the live lock go away. Cc: Yuanhan Liu <[email protected]> Cc: NeilBrown <[email protected]> Signed-off-by: Shaohua Li <[email protected]> Signed-off-by: Kamal Mostafa <[email protected]> --- drivers/md/raid5.c | 27 ++++++++------------------- drivers/md/raid5.h | 2 +- 2 files changed, 9 insertions(+), 20 deletions(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index a55b6859..71d7cf7 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -344,8 +344,7 @@ static void release_inactive_stripe_list(struct r5conf *conf, int hash) { int size; - unsigned long do_wakeup = 0; - int i = 0; + bool do_wakeup = false; unsigned long flags; if (hash == NR_STRIPE_HASH_LOCKS) { @@ -366,19 +365,15 @@ static void release_inactive_stripe_list(struct r5conf *conf, !list_empty(list)) atomic_dec(&conf->empty_inactive_list_nr); list_splice_tail_init(list, conf->inactive_list + hash); - do_wakeup |= 1 << hash; + do_wakeup = true; spin_unlock_irqrestore(conf->hash_locks + hash, flags); } size--; hash--; } - for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++) { - if (do_wakeup & (1 << i)) - wake_up(&conf->wait_for_stripe[i]); - } - if (do_wakeup) { + wake_up(&conf->wait_for_stripe); if (atomic_read(&conf->active_stripes) == 0) wake_up(&conf->wait_for_quiescent); if (conf->retry_read_aligned) @@ -691,15 +686,14 @@ get_active_stripe(struct r5conf *conf, sector_t sector, if (!sh) { set_bit(R5_INACTIVE_BLOCKED, &conf->cache_state); - wait_event_exclusive_cmd( - conf->wait_for_stripe[hash], + wait_event_lock_irq( + conf->wait_for_stripe, !list_empty(conf->inactive_list + hash) && (atomic_read(&conf->active_stripes) < (conf->max_nr_stripes * 3 / 4) || !test_bit(R5_INACTIVE_BLOCKED, &conf->cache_state)), - spin_unlock_irq(conf->hash_locks + hash), - spin_lock_irq(conf->hash_locks + hash)); + *(conf->hash_locks + hash)); clear_bit(R5_INACTIVE_BLOCKED, &conf->cache_state); } else { @@ -724,9 +718,6 @@ get_active_stripe(struct r5conf *conf, sector_t sector, } } while (sh == NULL); - if (!list_empty(conf->inactive_list + hash)) - wake_up(&conf->wait_for_stripe[hash]); - spin_unlock_irq(conf->hash_locks + hash); return sh; } @@ -2204,7 +2195,7 @@ static int resize_stripes(struct r5conf *conf, int newsize) cnt = 0; list_for_each_entry(nsh, &newstripes, lru) { lock_device_hash_lock(conf, hash); - wait_event_exclusive_cmd(conf->wait_for_stripe[hash], + wait_event_cmd(conf->wait_for_stripe, !list_empty(conf->inactive_list + hash), unlock_device_hash_lock(conf, hash), lock_device_hash_lock(conf, hash)); @@ -6487,9 +6478,7 @@ static struct r5conf *setup_conf(struct mddev *mddev) seqcount_init(&conf->gen_lock); mutex_init(&conf->cache_size_mutex); init_waitqueue_head(&conf->wait_for_quiescent); - for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++) { - init_waitqueue_head(&conf->wait_for_stripe[i]); - } + init_waitqueue_head(&conf->wait_for_stripe); init_waitqueue_head(&conf->wait_for_overlap); INIT_LIST_HEAD(&conf->handle_list); INIT_LIST_HEAD(&conf->hold_list); diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h index 65ecd49..a42a25d 100644 --- a/drivers/md/raid5.h +++ b/drivers/md/raid5.h @@ -515,7 +515,7 @@ struct r5conf { atomic_t empty_inactive_list_nr; struct llist_head released_stripes; wait_queue_head_t wait_for_quiescent; - wait_queue_head_t wait_for_stripe[NR_STRIPE_HASH_LOCKS]; + wait_queue_head_t wait_for_stripe; wait_queue_head_t wait_for_overlap; unsigned long cache_state; #define R5_INACTIVE_BLOCKED 1 /* release of inactive stripes blocked, -- 2.7.4
