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authorShaohua Li <shli@fb.com>2016-02-25 16:24:42 -0800
committerShaohua Li <shli@fb.com>2016-02-26 09:44:56 -0800
commit6ab2a4b806ae21b6c3e47c5ff1285ec06d505325 (patch)
tree881693ece12cd8ce147f1a370370eb60928120b0 /drivers/md
parent27a353c026a879a1001e5eac4bda75b16262c44a (diff)
RAID5: revert e9e4c377e2f563 to fix a livelock
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: stable@vger.kernel.org (v4.2+) Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com> Cc: NeilBrown <neilb@suse.de> Signed-off-by: Shaohua Li <shli@fb.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/raid5.c27
-rw-r--r--drivers/md/raid5.h2
2 files changed, 9 insertions, 20 deletions
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index b628cd525b32..c25f2fb2e567 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -340,8 +340,7 @@ 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) {
@@ -362,19 +361,15 @@ 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)
@@ -687,15 +682,14 @@ raid5_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 {
@@ -720,9 +714,6 @@ raid5_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;
}
@@ -2202,7 +2193,7 @@ 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));
@@ -6521,9 +6512,7 @@ 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 ae6068deefdf..517d4b68a1be 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -524,7 +524,7 @@ 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,