bcache: Allocator cleanup/fixes

The main fix is that bch_allocator_thread() wasn't waiting on
garbage collection to finish (if invalidate_buckets had set
ca->invalidate_needs_gc); we need that to make sure the allocator
doesn't spin and potentially block gc from finishing.

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

2 files changed, 50 insertions, 25 deletions

diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index 2879487d036a..048f2947e08b 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -243,31 +243,37 @@ static void invalidate_buckets_lru(struct cache *ca)
         ca->heap.used = 0;
 
         for_each_bucket(b, ca) {
+                /*
+                 * If we fill up the unused list, if we then return before
+                 * adding anything to the free_inc list we'll skip writing
+                 * prios/gens and just go back to allocating from the unused
+                 * list:
+                 */
+                if (fifo_full(&ca->unused))
+                        return;
+
                 if (!can_invalidate_bucket(ca, b))
                         continue;
 
-                if (!GC_SECTORS_USED(b)) {
-                        if (!bch_bucket_add_unused(ca, b))
-                                return;
-                } else {
-                        if (!heap_full(&ca->heap))
-                                heap_add(&ca->heap, b, bucket_max_cmp);
-                        else if (bucket_max_cmp(b, heap_peek(&ca->heap))) {
-                                ca->heap.data[0] = b;
-                                heap_sift(&ca->heap, 0, bucket_max_cmp);
-                        }
+                if (!GC_SECTORS_USED(b) &&
+                    bch_bucket_add_unused(ca, b))
+                        continue;
+
+                if (!heap_full(&ca->heap))
+                        heap_add(&ca->heap, b, bucket_max_cmp);
+                else if (bucket_max_cmp(b, heap_peek(&ca->heap))) {
+                        ca->heap.data[0] = b;
+                        heap_sift(&ca->heap, 0, bucket_max_cmp);
                 }
         }
 
-        if (ca->heap.used * 2 < ca->heap.size)
-                bch_queue_gc(ca->set);
-
         for (i = ca->heap.used / 2 - 1; i >= 0; --i)
                 heap_sift(&ca->heap, i, bucket_min_cmp);
 
         while (!fifo_full(&ca->free_inc)) {
                 if (!heap_pop(&ca->heap, b, bucket_min_cmp)) {
-                        /* We don't want to be calling invalidate_buckets()
+                        /*
+                         * We don't want to be calling invalidate_buckets()
                          * multiple times when it can't do anything
                          */
                         ca->invalidate_needs_gc = 1;
@@ -343,15 +349,22 @@ static void invalidate_buckets(struct cache *ca)
                 invalidate_buckets_random(ca);
                 break;
         }
+
+        pr_debug("free %zu/%zu free_inc %zu/%zu unused %zu/%zu",
+                 fifo_used(&ca->free), ca->free.size,
+                 fifo_used(&ca->free_inc), ca->free_inc.size,
+                 fifo_used(&ca->unused), ca->unused.size);
 }
 
 #define allocator_wait(ca, cond)                                        \
 do {                                                                    \
         DEFINE_WAIT(__wait);                                            \
                                                                         \
-        while (!(cond)) {                                               \
+        while (1) {                                                     \
                 prepare_to_wait(&ca->set->alloc_wait,                   \
                                 &__wait, TASK_INTERRUPTIBLE);           \
+                if (cond)                                               \
+                        break;                                          \
                                                                         \
                 mutex_unlock(&(ca)->set->bucket_lock);                  \
                 if (test_bit(CACHE_SET_STOPPING_2, &ca->set->flags)) {  \
@@ -360,7 +373,6 @@ do {									\
                 }                                                       \
                                                                         \
                 schedule();                                             \
-                __set_current_state(TASK_RUNNING);                      \
                 mutex_lock(&(ca)->set->bucket_lock);                    \
         }                                                               \
                                                                         \
@@ -374,6 +386,11 @@ void bch_allocator_thread(struct closure *cl)
         mutex_lock(&ca->set->bucket_lock);
 
         while (1) {
+                /*
+                 * First, we pull buckets off of the unused and free_inc lists,
+                 * possibly issue discards to them, then we add the bucket to
+                 * the free list:
+                 */
                 while (1) {
                         long bucket;
 
@@ -398,17 +415,26 @@ void bch_allocator_thread(struct closure *cl)
                         }
                 }
 
-                allocator_wait(ca, ca->set->gc_mark_valid);
-                invalidate_buckets(ca);
+                /*
+                 * We've run out of free buckets, we need to find some buckets
+                 * we can invalidate. First, invalidate them in memory and add
+                 * them to the free_inc list:
+                 */
 
-                allocator_wait(ca, !atomic_read(&ca->set->prio_blocked) ||
-                               !CACHE_SYNC(&ca->set->sb));
+                allocator_wait(ca, ca->set->gc_mark_valid &&
+                               (ca->need_save_prio > 64 ||
+                                !ca->invalidate_needs_gc));
+                invalidate_buckets(ca);
 
+                /*
+                 * Now, we write their new gens to disk so we can start writing
+                 * new stuff to them:
+                 */
+                allocator_wait(ca, !atomic_read(&ca->set->prio_blocked));
                 if (CACHE_SYNC(&ca->set->sb) &&
                     (!fifo_empty(&ca->free_inc) ||
-                     ca->need_save_prio > 64)) {
+                     ca->need_save_prio > 64))
                         bch_prio_write(ca);
-                }
         }
 }
 
@@ -475,7 +501,7 @@ void bch_bucket_free(struct cache_set *c, struct bkey *k)
         for (i = 0; i < KEY_PTRS(k); i++) {
                 struct bucket *b = PTR_BUCKET(c, k, i);
 
-                SET_GC_MARK(b, 0);
+                SET_GC_MARK(b, GC_MARK_RECLAIMABLE);
                 SET_GC_SECTORS_USED(b, 0);
                 bch_bucket_add_unused(PTR_CACHE(c, k, i), b);
         }
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 852340793777..7a5658f04e62 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -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))
-                closure_wake_up(&b->c->bucket_wait);
+                wake_up(&b->c->alloc_wait);
 
         b->prio_blocked = 0;
 
@@ -1548,7 +1548,6 @@ static void bch_btree_gc(struct closure *cl)
 
         trace_bcache_gc_end(c->sb.set_uuid);
         wake_up(&c->alloc_wait);
-        closure_wake_up(&c->bucket_wait);
 
         continue_at(cl, bch_moving_gc, bch_gc_wq);
 }