bcache: rip out generational gc

generational copygc has the side effect of potentially fragmenting data,
we probably don't do it by default, if at all

5 files changed, 12 insertions, 50 deletions

diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index 3b6ad78ecb9e..ce335693bb44 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -1671,9 +1671,7 @@ void bch_cache_allocator_stop(struct cache *ca)
 	for (i = 0; i < ARRAY_SIZE(c->write_points); i++)
 		bch_stop_write_point(ca, &c->write_points[i]);
 
-	for (i = 0; i < ARRAY_SIZE(ca->gc_buckets); i++)
-		bch_stop_write_point(ca, &ca->gc_buckets[i]);
-
+	bch_stop_write_point(ca, &ca->copygc_write_point);
 	bch_stop_write_point(ca, &c->promote_write_point);
 	bch_stop_write_point(ca, &ca->tiering_write_point);
 	bch_stop_write_point(ca, &c->migration_write_point);
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index fee1c37a9486..36bf8841c3d4 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -437,13 +437,7 @@ struct cache {
 	struct write_point	tiering_write_point;
 	unsigned		tiering_stripe_size;
 
-	/*
-	 * open buckets used in moving garbage collection
-	 * NOTE: GC_GEN == 0 signifies no moving gc, so accessing the
-	 * gc_buckets array is always GC_GEN-1.
-	 */
-#define NUM_GC_GENS 8
-	struct write_point	gc_buckets[NUM_GC_GENS];
+	struct write_point	copygc_write_point;
 
 	struct journal_device	journal;
 
diff --git a/drivers/md/bcache/movinggc.c b/drivers/md/bcache/movinggc.c
index 1e6661b00ab9..e8221054a7a8 100644
--- a/drivers/md/bcache/movinggc.c
+++ b/drivers/md/bcache/movinggc.c
@@ -49,20 +49,16 @@ static int issue_moving_gc_move(struct cache *ca,
 	struct cache_set *c = ca->set;
 	const struct bch_extent_ptr *ptr;
 	struct moving_io *io;
-	unsigned gen;
 
 	extent_for_each_ptr(bkey_s_c_to_extent(k), ptr)
 		if ((ca->sb.nr_this_dev == ptr->dev) &&
-		    (gen = PTR_BUCKET(ca, ptr)->copygc_gen))
+		    PTR_BUCKET(ca, ptr)->copygc_gen)
 			goto found;
 
 	/* We raced - bucket's been reused */
 	return 0;
 found:
-	gen--;
-	BUG_ON(gen > ARRAY_SIZE(ca->gc_buckets));
-
-	io = moving_io_alloc(c, q, &ca->gc_buckets[gen], k, ptr);
+	io = moving_io_alloc(c, q, &ca->copygc_write_point, k, ptr);
 	if (!io) {
 		trace_bcache_moving_gc_alloc_fail(c, k.k->size);
 		return -ENOMEM;
@@ -135,7 +131,7 @@ static void bch_moving_gc(struct cache *ca)
 {
 	struct cache_set *c = ca->set;
 	struct bucket *g;
-	u64 sectors_to_move, sectors_gen, gen_current, sectors_total;
+	u64 sectors_to_move;
 	size_t buckets_to_move, buckets_unused = 0;
 	struct bucket_heap_entry e;
 	unsigned sectors_used, i;
@@ -209,32 +205,10 @@ static void bch_moving_gc(struct cache *ca)
 		sectors_to_move -= e.val;
 	}
 
-	buckets_to_move = ca->heap.used;
-
-	/*
-	 * resort by write_prio to group into generations, attempts to
-	 * keep hot and cold data in the same locality.
-	 */
-
-	for (i = 0; i < ca->heap.used; i++) {
-		struct bucket_heap_entry *e = &ca->heap.data[i];
-
-		e->val = (c->prio_clock[WRITE].hand - e->g->write_prio);
-	}
-
-	heap_resort(&ca->heap, bucket_max_cmp);
-
-	sectors_gen = sectors_to_move / NUM_GC_GENS;
-	gen_current = 1;
-	sectors_total = 0;
+	for (i = 0; i < ca->heap.used; i++)
+		ca->heap.data[i].g->copygc_gen = 1;
 
-	while (heap_pop(&ca->heap, e, bucket_max_cmp)) {
-		sectors_total += bucket_sectors_used(e.g);
-		e.g->copygc_gen = gen_current;
-		if (gen_current < NUM_GC_GENS &&
-		    sectors_total >= sectors_gen * gen_current)
-			gen_current++;
-	}
+	buckets_to_move = ca->heap.used;
 
 	mutex_unlock(&ca->set->bucket_lock);
 	mutex_unlock(&ca->heap_lock);
diff --git a/drivers/md/bcache/movinggc.h b/drivers/md/bcache/movinggc.h
index 45496a31a95f..6ee8db55f44a 100644
--- a/drivers/md/bcache/movinggc.h
+++ b/drivers/md/bcache/movinggc.h
@@ -21,8 +21,7 @@
  * fragmentation from the multiple write points for each generation:
  */
 #define COPYGC_SECTORS_PER_ITER(ca)					\
-	((ca)->mi.bucket_size *						\
-	 (COPYGC_BUCKETS_PER_ITER(ca) - (NUM_GC_GENS - 1)))
+	((ca)->mi.bucket_size *	COPYGC_BUCKETS_PER_ITER(ca))
 
 int bch_moving_init_cache(struct cache *);
 void bch_moving_gc_stop(struct cache *);
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index d1e95f10b488..ea4ced7b5de0 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1953,8 +1953,7 @@ static const char *cache_alloc(struct bcache_superblock *sb,
 	ca->bucket_bits = ilog2(ca->mi.bucket_size);
 
 	/* XXX: tune these */
-	movinggc_reserve = max_t(size_t, NUM_GC_GENS * 4,
-				 ca->mi.nbuckets >> 7);
+	movinggc_reserve = max_t(size_t, 16, ca->mi.nbuckets >> 7);
 	reserve_none = max_t(size_t, 4, ca->mi.nbuckets >> 9);
 	/*
 	 * free_inc must be smaller than the copygc reserve: if it was bigger,
@@ -1996,10 +1995,8 @@ static const char *cache_alloc(struct bcache_superblock *sb,
 		total_reserve += ca->free[i].size;
 	pr_debug("%zu buckets reserved", total_reserve);
 
-	for (i = 0; i < ARRAY_SIZE(ca->gc_buckets); i++) {
-		ca->gc_buckets[i].reserve = RESERVE_MOVINGGC;
-		ca->gc_buckets[i].group = &ca->self;
-	}
+	ca->copygc_write_point.reserve = RESERVE_MOVINGGC;
+	ca->copygc_write_point.group = &ca->self;
 
 	ca->tiering_write_point.reserve = RESERVE_NONE;
 	ca->tiering_write_point.group = &ca->self;