[PATCH v2] bcache: allow allocator to invalidate bucket in gc

[Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx>]

Currently, if the gc is running, when the allocator found free_inc
is empty, allocator has to wait the gc finish. Before that, the
IO is blocked.

But actually, there would be some buckets is reclaimable before gc,
and gc will never mark this kind of bucket to be  unreclaimable.

So we can put these buckets into free_inc in gc running to avoid
IO being blocked.

Signed-off-by: Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx>
---
 drivers/md/bcache/alloc.c  | 11 +++++------
 drivers/md/bcache/bcache.h |  1 +
 drivers/md/bcache/btree.c  | 10 +++++++++-
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index 52035a7..faa5a5d 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -130,12 +130,11 @@ static inline bool can_inc_bucket_gen(struct bucket *b)
 
 bool bch_can_invalidate_bucket(struct cache *ca, struct bucket *b)
 {
-	BUG_ON(!ca->set->gc_mark_valid);
-
-	return (!GC_MARK(b) ||
+	return ((b->reclaimable_in_gc || ca->set->gc_mark_valid) &&
+		((!GC_MARK(b) ||
 		GC_MARK(b) == GC_MARK_RECLAIMABLE) &&
 		!atomic_read(&b->pin) &&
-		can_inc_bucket_gen(b);
+		can_inc_bucket_gen(b)));
 }
 
 void __bch_invalidate_one_bucket(struct cache *ca, struct bucket *b)
@@ -149,6 +148,7 @@ void __bch_invalidate_one_bucket(struct cache *ca, struct bucket *b)
 	bch_inc_gen(ca, b);
 	b->prio = INITIAL_PRIO;
 	atomic_inc(&b->pin);
+	b->reclaimable_in_gc = 0;
 }
 
 static void bch_invalidate_one_bucket(struct cache *ca, struct bucket *b)
@@ -353,8 +353,7 @@ static int bch_allocator_thread(void *arg)
 		 */
 
 retry_invalidate:
-		allocator_wait(ca, ca->set->gc_mark_valid &&
-			       !ca->invalidate_needs_gc);
+		allocator_wait(ca, !ca->invalidate_needs_gc);
 		invalidate_buckets(ca);
 
 		/*
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 4fd03d2..870f146 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -200,6 +200,7 @@ struct bucket {
 	uint8_t		gen;
 	uint8_t		last_gc; /* Most out of date gen in the btree */
 	uint16_t	gc_mark; /* Bitfield used by GC. See below for field */
+	uint16_t	reclaimable_in_gc:1;
 };
 
 /*
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 3d8bd06..d45a1dd 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1702,18 +1702,21 @@ static void btree_gc_start(struct cache_set *c)
 
 	mutex_lock(&c->bucket_lock);
 
-	c->gc_mark_valid = 0;
 	c->gc_done = ZERO_KEY;
 
 	for_each_cache(ca, c, i)
 		for_each_bucket(b, ca) {
 			b->last_gc = b->gen;
+			if (bch_can_invalidate_bucket(ca, b))
+				b->reclaimable_in_gc = 1;
+
 			if (!atomic_read(&b->pin)) {
 				SET_GC_MARK(b, 0);
 				SET_GC_SECTORS_USED(b, 0);
 			}
 		}
 
+	c->gc_mark_valid = 0;
 	mutex_unlock(&c->bucket_lock);
 }
 
@@ -1729,6 +1732,11 @@ static void bch_btree_gc_finish(struct cache_set *c)
 	c->gc_mark_valid = 1;
 	c->need_gc	= 0;
 
+	for_each_cache(ca, c, i)
+		for_each_bucket(b, ca)
+			if (b->reclaimable_in_gc)
+				b->reclaimable_in_gc = 0;
+
 	for (i = 0; i < KEY_PTRS(&c->uuid_bucket); i++)
 		SET_GC_MARK(PTR_BUCKET(c, &c->uuid_bucket, i),
 			    GC_MARK_METADATA);
-- 
1.8.3.1