sbitmap: push per-cpu last_tag into sbitmap_queue

Allocating your own per-cpu allocation hint separately makes for an
awkward API. Instead, allocate the per-cpu hint as part of the struct
sbitmap_queue. There's no point for a struct sbitmap_queue without the
cache, but you can still use a bare struct sbitmap.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

4 files changed, 20 insertions, 40 deletions

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 2cbdecd..c9a22db 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -94,39 +94,21 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
 #define BT_ALLOC_RR(tags) (tags->alloc_policy == BLK_TAG_ALLOC_RR)
 
 static int __bt_get(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
-		    unsigned int *tag_cache, struct blk_mq_tags *tags)
+		    struct blk_mq_tags *tags)
 {
-	unsigned int last_tag;
-	int tag;
-
 	if (!hctx_may_queue(hctx, bt))
 		return -1;
-
-	last_tag = *tag_cache;
-	tag = sbitmap_get(&bt->sb, last_tag, BT_ALLOC_RR(tags));
-
-	if (tag == -1) {
-		*tag_cache = 0;
-	} else if (tag == last_tag || unlikely(BT_ALLOC_RR(tags))) {
-		last_tag = tag + 1;
-		if (last_tag >= bt->sb.depth - 1)
-			last_tag = 0;
-		*tag_cache = last_tag;
-	}
-
-	return tag;
+	return __sbitmap_queue_get(bt, BT_ALLOC_RR(tags));
 }
 
-static int bt_get(struct blk_mq_alloc_data *data,
-		  struct sbitmap_queue *bt,
-		  struct blk_mq_hw_ctx *hctx,
-		  unsigned int *last_tag, struct blk_mq_tags *tags)
+static int bt_get(struct blk_mq_alloc_data *data, struct sbitmap_queue *bt,
+		  struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags)
 {
 	struct sbq_wait_state *ws;
 	DEFINE_WAIT(wait);
 	int tag;
 
-	tag = __bt_get(hctx, bt, last_tag, tags);
+	tag = __bt_get(hctx, bt, tags);
 	if (tag != -1)
 		return tag;
 
@@ -137,7 +119,7 @@ static int bt_get(struct blk_mq_alloc_data *data,
 	do {
 		prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE);
 
-		tag = __bt_get(hctx, bt, last_tag, tags);
+		tag = __bt_get(hctx, bt, tags);
 		if (tag != -1)
 			break;
 
@@ -154,7 +136,7 @@ static int bt_get(struct blk_mq_alloc_data *data,
 		 * Retry tag allocation after running the hardware queue,
 		 * as running the queue may also have found completions.
 		 */
-		tag = __bt_get(hctx, bt, last_tag, tags);
+		tag = __bt_get(hctx, bt, tags);
 		if (tag != -1)
 			break;
 
@@ -168,7 +150,6 @@ static int bt_get(struct blk_mq_alloc_data *data,
 		if (data->flags & BLK_MQ_REQ_RESERVED) {
 			bt = &data->hctx->tags->breserved_tags;
 		} else {
-			last_tag = &data->ctx->last_tag;
 			hctx = data->hctx;
 			bt = &hctx->tags->bitmap_tags;
 		}
@@ -185,7 +166,7 @@ static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data)
 	int tag;
 
 	tag = bt_get(data, &data->hctx->tags->bitmap_tags, data->hctx,
-			&data->ctx->last_tag, data->hctx->tags);
+		     data->hctx->tags);
 	if (tag >= 0)
 		return tag + data->hctx->tags->nr_reserved_tags;
 
@@ -194,15 +175,15 @@ static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data)
 
 static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data)
 {
-	int tag, zero = 0;
+	int tag;
 
 	if (unlikely(!data->hctx->tags->nr_reserved_tags)) {
 		WARN_ON_ONCE(1);
 		return BLK_MQ_TAG_FAIL;
 	}
 
-	tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero,
-		data->hctx->tags);
+	tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL,
+		     data->hctx->tags);
 	if (tag < 0)
 		return BLK_MQ_TAG_FAIL;
 
@@ -216,8 +197,8 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 	return __blk_mq_get_tag(data);
 }
 
-void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag,
-		    unsigned int *last_tag)
+void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
+		    unsigned int tag)
 {
 	struct blk_mq_tags *tags = hctx->tags;
 
@@ -225,12 +206,12 @@ void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag,
 		const int real_tag = tag - tags->nr_reserved_tags;
 
 		BUG_ON(real_tag >= tags->nr_tags);
-		sbitmap_queue_clear(&tags->bitmap_tags, real_tag);
-		if (likely(tags->alloc_policy == BLK_TAG_ALLOC_FIFO))
-			*last_tag = real_tag;
+		sbitmap_queue_clear(&tags->bitmap_tags, real_tag,
+				    BT_ALLOC_RR(tags), ctx->cpu);
 	} else {
 		BUG_ON(tag >= tags->nr_reserved_tags);
-		sbitmap_queue_clear(&tags->breserved_tags, tag);
+		sbitmap_queue_clear(&tags->breserved_tags, tag,
+				    BT_ALLOC_RR(tags), ctx->cpu);
 	}
 }
 
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index 3215c08..2b1d52e 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -27,7 +27,8 @@ extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int r
 extern void blk_mq_free_tags(struct blk_mq_tags *tags);
 
 extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data);
-extern void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag, unsigned int *last_tag);
+extern void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
+			   unsigned int tag);
 extern bool blk_mq_has_free_tags(struct blk_mq_tags *tags);
 extern ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page);
 extern void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *last_tag);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6603be1..e0a69da 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -303,7 +303,7 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx,
 	rq->cmd_flags = 0;
 
 	clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
-	blk_mq_put_tag(hctx, tag, &ctx->last_tag);
+	blk_mq_put_tag(hctx, ctx, tag);
 	blk_queue_exit(q);
 }
 
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 71831f9..9b15d2e 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -12,8 +12,6 @@ struct blk_mq_ctx {
 	unsigned int		cpu;
 	unsigned int		index_hw;
 
-	unsigned int		last_tag ____cacheline_aligned_in_smp;
-
 	/* incremented at dispatch time */
 	unsigned long		rq_dispatched[2];
 	unsigned long		rq_merged;