2 files changed, 49 insertions, 3 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 78ea44336e75..287cc3b30043 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -239,12 +239,47 @@ static void __release_stripe(struct r5conf *conf, struct stripe_head *sh)
                 do_release_stripe(conf, sh);
 }
 
+/* should hold conf->device_lock already */
+static int release_stripe_list(struct r5conf *conf)
+{
+        struct stripe_head *sh;
+        int count = 0;
+        struct llist_node *head;
+
+        head = llist_del_all(&conf->released_stripes);
+        while (head) {
+                sh = llist_entry(head, struct stripe_head, release_list);
+                head = llist_next(head);
+                /* sh could be readded after STRIPE_ON_RELEASE_LIST is cleard */
+                smp_mb();
+                clear_bit(STRIPE_ON_RELEASE_LIST, &sh->state);
+                /*
+                 * Don't worry the bit is set here, because if the bit is set
+                 * again, the count is always > 1. This is true for
+                 * STRIPE_ON_UNPLUG_LIST bit too.
+                 */
+                __release_stripe(conf, sh);
+                count++;
+        }
+
+        return count;
+}
+
 static void release_stripe(struct stripe_head *sh)
 {
         struct r5conf *conf = sh->raid_conf;
         unsigned long flags;
+        bool wakeup;
 
+        if (test_and_set_bit(STRIPE_ON_RELEASE_LIST, &sh->state))
+                goto slow_path;
+        wakeup = llist_add(&sh->release_list, &conf->released_stripes);
+        if (wakeup)
+                md_wakeup_thread(conf->mddev->thread);
+        return;
+slow_path:
         local_irq_save(flags);
+        /* we are ok here if STRIPE_ON_RELEASE_LIST is set or not */
         if (atomic_dec_and_lock(&sh->count, &conf->device_lock)) {
                 do_release_stripe(conf, sh);
                 spin_unlock(&conf->device_lock);
@@ -491,7 +526,8 @@ get_active_stripe(struct r5conf *conf, sector_t sector,
                         if (atomic_read(&sh->count)) {
                                 BUG_ON(!list_empty(&sh->lru)
                                     && !test_bit(STRIPE_EXPANDING, &sh->state)
-                                    && !test_bit(STRIPE_ON_UNPLUG_LIST, &sh->state));
+                                    && !test_bit(STRIPE_ON_UNPLUG_LIST, &sh->state)
+                                    && !test_bit(STRIPE_ON_RELEASE_LIST, &sh->state));
                         } else {
                                 if (!test_bit(STRIPE_HANDLE, &sh->state))
                                         atomic_inc(&conf->active_stripes);
@@ -4127,6 +4163,10 @@ static void raid5_unplug(struct blk_plug_cb *blk_cb, bool from_schedule)
                          */
                         smp_mb__before_clear_bit();
                         clear_bit(STRIPE_ON_UNPLUG_LIST, &sh->state);
+                        /*
+                         * STRIPE_ON_RELEASE_LIST could be set here. In that
+                         * case, the count is always > 1 here
+                         */
                         __release_stripe(conf, sh);
                         cnt++;
                 }
@@ -4836,7 +4876,9 @@ static void raid5d(struct md_thread *thread)
         spin_lock_irq(&conf->device_lock);
         while (1) {
                 struct bio *bio;
-                int batch_size;
+                int batch_size, released;
+
+                released = release_stripe_list(conf);
 
                 if (
                     !list_empty(&conf->bitmap_list)) {
@@ -4861,7 +4903,7 @@ static void raid5d(struct md_thread *thread)
                 }
 
                 batch_size = handle_active_stripes(conf);
-                if (!batch_size)
+                if (!batch_size && !released)
                         break;
                 handled += batch_size;
 
@@ -5176,6 +5218,7 @@ static struct r5conf *setup_conf(struct mddev *mddev)
         INIT_LIST_HEAD(&conf->delayed_list);
         INIT_LIST_HEAD(&conf->bitmap_list);
         INIT_LIST_HEAD(&conf->inactive_list);
+        init_llist_head(&conf->released_stripes);
         atomic_set(&conf->active_stripes, 0);
         atomic_set(&conf->preread_active_stripes, 0);
         atomic_set(&conf->active_aligned_reads, 0);
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 70c49329ca9a..a98f99d2a58f 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -197,6 +197,7 @@ enum reconstruct_states {
 struct stripe_head {
         struct hlist_node       hash;
         struct list_head        lru;          /* inactive_list or handle_list */
+        struct llist_node       release_list;
         struct r5conf           *raid_conf;
         short                   generation;     /* increments with every
                                                  * reshape */
@@ -321,6 +322,7 @@ enum {
         STRIPE_OPS_REQ_PENDING,
         STRIPE_ON_UNPLUG_LIST,
         STRIPE_DISCARD,
+        STRIPE_ON_RELEASE_LIST,
 };
 
 /*
@@ -445,6 +447,7 @@ struct r5conf {
          */
         atomic_t                active_stripes;
         struct list_head        inactive_list;
+        struct llist_head       released_stripes;
         wait_queue_head_t       wait_for_stripe;
         wait_queue_head_t       wait_for_overlap;
         int                     inactive_blocked;       /* release of inactive stripes blocked,