4.2.8-ckt7 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Shaohua Li <shli@xxxxxx>
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 <yuanhan.liu@xxxxxxxxxxxxxxx>
Cc: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
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
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