bcache: Convert allocator thread to kthread

Using a workqueue when we just want a single thread is a bit silly.

Signed-off-by: Kent Overstreet <koverstreet@google.com>

4 files changed, 43 insertions, 33 deletions

diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index 048f2947e08b..38428f46ea74 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -63,6 +63,7 @@
 #include "bcache.h"
 #include "btree.h"
 
+#include <linux/kthread.h>
 #include <linux/random.h>
 
 #define MAX_IN_FLIGHT_DISCARDS          8U
@@ -151,7 +152,7 @@ static void discard_finish(struct work_struct *w)
         mutex_unlock(&ca->set->bucket_lock);
 
         closure_wake_up(&ca->set->bucket_wait);
-        wake_up(&ca->set->alloc_wait);
+        wake_up_process(ca->alloc_thread);
 
         closure_put(&ca->set->cl);
 }
@@ -358,30 +359,26 @@ static void invalidate_buckets(struct cache *ca)
 
 #define allocator_wait(ca, cond)                                        \
 do {                                                                    \
-        DEFINE_WAIT(__wait);                                            \
-                                                                        \
         while (1) {                                                     \
-                prepare_to_wait(&ca->set->alloc_wait,                   \
-                                &__wait, TASK_INTERRUPTIBLE);           \
+                set_current_state(TASK_INTERRUPTIBLE);                  \
                 if (cond)                                               \
                         break;                                          \
                                                                         \
                 mutex_unlock(&(ca)->set->bucket_lock);                  \
                 if (test_bit(CACHE_SET_STOPPING_2, &ca->set->flags)) {  \
-                        finish_wait(&ca->set->alloc_wait, &__wait);     \
-                        closure_return(cl);                             \
+                        closure_put(&ca->set->cl);                      \
+                        return 0;                                       \
                 }                                                       \
                                                                         \
                 schedule();                                             \
                 mutex_lock(&(ca)->set->bucket_lock);                    \
         }                                                               \
-                                                                        \
-        finish_wait(&ca->set->alloc_wait, &__wait);                     \
+        __set_current_state(TASK_RUNNING);                              \
 } while (0)
 
-void bch_allocator_thread(struct closure *cl)
+static int bch_allocator_thread(void *arg)
 {
-        struct cache *ca = container_of(cl, struct cache, alloc);
+        struct cache *ca = arg;
 
         mutex_lock(&ca->set->bucket_lock);
 
@@ -442,7 +439,7 @@ long bch_bucket_alloc(struct cache *ca, unsigned watermark, struct closure *cl)
 {
         long r = -1;
 again:
-        wake_up(&ca->set->alloc_wait);
+        wake_up_process(ca->alloc_thread);
 
         if (fifo_used(&ca->free) > ca->watermark[watermark] &&
             fifo_pop(&ca->free, r)) {
@@ -552,6 +549,19 @@ int bch_bucket_alloc_set(struct cache_set *c, unsigned watermark,
 
 /* Init */
 
+int bch_cache_allocator_start(struct cache *ca)
+{
+        ca->alloc_thread = kthread_create(bch_allocator_thread,
+                                          ca, "bcache_allocator");
+        if (IS_ERR(ca->alloc_thread))
+                return PTR_ERR(ca->alloc_thread);
+
+        closure_get(&ca->set->cl);
+        wake_up_process(ca->alloc_thread);
+
+        return 0;
+}
+
 void bch_cache_allocator_exit(struct cache *ca)
 {
         struct discard *d;
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index d3e15b42a4ab..166c8ddc0be4 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -565,8 +565,7 @@ struct cache {
 
         unsigned                watermark[WATERMARK_MAX];
 
-        struct closure          alloc;
-        struct workqueue_struct *alloc_workqueue;
+        struct task_struct      *alloc_thread;
 
         struct closure          prio;
         struct prio_set         *disk_buckets;
@@ -703,9 +702,6 @@ struct cache_set {
         /* For the btree cache */
         struct shrinker         shrink;
 
-        /* For the allocator itself */
-        wait_queue_head_t       alloc_wait;
-
         /* For the btree cache and anything allocation related */
         struct mutex            bucket_lock;
 
@@ -1173,6 +1169,15 @@ static inline uint8_t bucket_disk_gen(struct bucket *b)
         static struct kobj_attribute ksysfs_##n =                       \
                 __ATTR(n, S_IWUSR|S_IRUSR, show, store)
 
+static inline void wake_up_allocators(struct cache_set *c)
+{
+        struct cache *ca;
+        unsigned i;
+
+        for_each_cache(ca, c, i)
+                wake_up_process(ca->alloc_thread);
+}
+
 /* Forward declarations */
 
 void bch_writeback_queue(struct cached_dev *);
@@ -1193,7 +1198,6 @@ void bch_submit_bbio(struct bio *, struct cache_set *, struct bkey *, unsigned);
 uint8_t bch_inc_gen(struct cache *, struct bucket *);
 void bch_rescale_priorities(struct cache_set *, int);
 bool bch_bucket_add_unused(struct cache *, struct bucket *);
-void bch_allocator_thread(struct closure *);
 
 long bch_bucket_alloc(struct cache *, unsigned, struct closure *);
 void bch_bucket_free(struct cache_set *, struct bkey *);
@@ -1244,6 +1248,7 @@ int bch_btree_cache_alloc(struct cache_set *);
 void bch_cached_dev_writeback_init(struct cached_dev *);
 void bch_moving_init_cache_set(struct cache_set *);
 
+int bch_cache_allocator_start(struct cache *ca);
 void bch_cache_allocator_exit(struct cache *ca);
 int bch_cache_allocator_init(struct cache *ca);
 
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 7a5658f04e62..45b88fbffbe0 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -273,7 +273,7 @@ static void btree_complete_write(struct btree *b, struct btree_write *w)
 {
         if (w->prio_blocked &&
             !atomic_sub_return(w->prio_blocked, &b->c->prio_blocked))
-                wake_up(&b->c->alloc_wait);
+                wake_up_allocators(b->c);
 
         if (w->journal) {
                 atomic_dec_bug(w->journal);
@@ -984,7 +984,7 @@ static void btree_node_free(struct btree *b, struct btree_op *op)
 
         if (b->prio_blocked &&
             !atomic_sub_return(b->prio_blocked, &b->c->prio_blocked))
-                wake_up(&b->c->alloc_wait);
+                wake_up_allocators(b->c);
 
         b->prio_blocked = 0;
 
@@ -1547,7 +1547,7 @@ static void bch_btree_gc(struct closure *cl)
         blktrace_msg_all(c, "Finished gc");
 
         trace_bcache_gc_end(c->sb.set_uuid);
-        wake_up(&c->alloc_wait);
+        wake_up_allocators(c);
 
         continue_at(cl, bch_moving_gc, bch_gc_wq);
 }
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 3de5626919ef..aaeda235fc75 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1282,7 +1282,7 @@ static void cache_set_flush(struct closure *cl)
 
         /* Shut down allocator threads */
         set_bit(CACHE_SET_STOPPING_2, &c->flags);
-        wake_up(&c->alloc_wait);
+        wake_up_allocators(c);
 
         bch_cache_accounting_destroy(&c->accounting);
 
@@ -1373,7 +1373,6 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
                 c->btree_pages = max_t(int, c->btree_pages / 4,
                                        BTREE_MAX_PAGES);
 
-        init_waitqueue_head(&c->alloc_wait);
         mutex_init(&c->bucket_lock);
         mutex_init(&c->fill_lock);
         mutex_init(&c->sort_lock);
@@ -1496,9 +1495,10 @@ static void run_cache_set(struct cache_set *c)
                  */
                 bch_journal_next(&c->journal);
 
+                err = "error starting allocator thread";
                 for_each_cache(ca, c, i)
-                        closure_call(&ca->alloc, bch_allocator_thread,
-                                     system_wq, &c->cl);
+                        if (bch_cache_allocator_start(ca))
+                                goto err;
 
                 /*
                  * First place it's safe to allocate: btree_check() and
@@ -1531,17 +1531,16 @@ static void run_cache_set(struct cache_set *c)
 
                 bch_btree_gc_finish(c);
 
+                err = "error starting allocator thread";
                 for_each_cache(ca, c, i)
-                        closure_call(&ca->alloc, bch_allocator_thread,
-                                     ca->alloc_workqueue, &c->cl);
+                        if (bch_cache_allocator_start(ca))
+                                goto err;
 
                 mutex_lock(&c->bucket_lock);
                 for_each_cache(ca, c, i)
                         bch_prio_write(ca);
                 mutex_unlock(&c->bucket_lock);
 
-                wake_up(&c->alloc_wait);
-
                 err = "cannot allocate new UUID bucket";
                 if (__uuid_write(c))
                         goto err_unlock_gc;
@@ -1673,9 +1672,6 @@ void bch_cache_release(struct kobject *kobj)
 
         bio_split_pool_free(&ca->bio_split_hook);
 
-        if (ca->alloc_workqueue)
-                destroy_workqueue(ca->alloc_workqueue);
-
         free_pages((unsigned long) ca->disk_buckets, ilog2(bucket_pages(ca)));
         kfree(ca->prio_buckets);
         vfree(ca->buckets);
@@ -1723,7 +1719,6 @@ static int cache_alloc(struct cache_sb *sb, struct cache *ca)
             !(ca->prio_buckets  = kzalloc(sizeof(uint64_t) * prio_buckets(ca) *
                                           2, GFP_KERNEL)) ||
             !(ca->disk_buckets  = alloc_bucket_pages(GFP_KERNEL, ca)) ||
-            !(ca->alloc_workqueue = alloc_workqueue("bch_allocator", 0, 1)) ||
             bio_split_pool_init(&ca->bio_split_hook))
                 return -ENOMEM;