[PATCH V7 4/9] blk-mq: support rq filter callback when iterating rqs

[Ming Lei <ming.lei@redhat.com>]

Now request is thought as in-flight only when its state is updated as
MQ_RQ_IN_FLIGHT, which is done by dirver via blk_mq_start_request().

Actually from blk-mq's view, one rq can be thought as in-flight
after its tag is >= 0.

Passing one rq filter callback so that we can iterating requests very
flexiable.

Meantime blk_mq_all_tag_busy_iter is defined as public, which will be
called from blk-mq internally.

Cc: John Garry <john.garry@huawei.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq-tag.c | 39 +++++++++++++++++++++++++++------------
 block/blk-mq-tag.h |  4 ++++
 2 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 586c9d6e904a..2e43b827c96d 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -255,6 +255,7 @@ static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
 struct bt_tags_iter_data {
 	struct blk_mq_tags *tags;
 	busy_tag_iter_fn *fn;
+	busy_rq_iter_fn *busy_rq_fn;
 	void *data;
 	bool reserved;
 };
@@ -274,7 +275,7 @@ static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 	 * test and set the bit before assining ->rqs[].
 	 */
 	rq = tags->rqs[bitnr];
-	if (rq && blk_mq_request_started(rq))
+	if (rq && iter_data->busy_rq_fn(rq, iter_data->data, reserved))
 		return iter_data->fn(rq, iter_data->data, reserved);
 
 	return true;
@@ -294,11 +295,13 @@ static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
  *		bitmap_tags member of struct blk_mq_tags.
  */
 static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
-			     busy_tag_iter_fn *fn, void *data, bool reserved)
+			     busy_tag_iter_fn *fn, busy_rq_iter_fn *busy_rq_fn,
+			     void *data, bool reserved)
 {
 	struct bt_tags_iter_data iter_data = {
 		.tags = tags,
 		.fn = fn,
+		.busy_rq_fn = busy_rq_fn,
 		.data = data,
 		.reserved = reserved,
 	};
@@ -310,19 +313,30 @@ static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
 /**
  * blk_mq_all_tag_busy_iter - iterate over all started requests in a tag map
  * @tags:	Tag map to iterate over.
- * @fn:		Pointer to the function that will be called for each started
- *		request. @fn will be called as follows: @fn(rq, @priv,
- *		reserved) where rq is a pointer to a request. 'reserved'
- *		indicates whether or not @rq is a reserved request. Return
- *		true to continue iterating tags, false to stop.
+ * @fn:		Pointer to the function that will be called for each request
+ * 		when .busy_rq_fn(rq) returns true. @fn will be called as
+ * 		follows: @fn(rq, @priv, reserved) where rq is a pointer to a
+ * 		request. 'reserved' indicates whether or not @rq is a reserved
+ * 		request. Return true to continue iterating tags, false to stop.
+ * @busy_rq_fn: Pointer to the function that will be called for each request,
+ * 		@busy_rq_fn's type is same with @fn. Only when @busy_rq_fn(rq,
+ * 		@priv, reserved) returns true, @fn will be called on this rq.
  * @priv:	Will be passed as second argument to @fn.
  */
-static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
-		busy_tag_iter_fn *fn, void *priv)
+void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
+		busy_tag_iter_fn *fn, busy_rq_iter_fn *busy_rq_fn,
+		void *priv)
 {
 	if (tags->nr_reserved_tags)
-		bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
-	bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
+		bt_tags_for_each(tags, &tags->breserved_tags, fn, busy_rq_fn,
+				priv, true);
+	bt_tags_for_each(tags, &tags->bitmap_tags, fn, busy_rq_fn, priv, false);
+}
+
+static bool blk_mq_default_busy_rq(struct request *rq, void *data,
+		bool reserved)
+{
+	return blk_mq_request_started(rq);
 }
 
 /**
@@ -342,7 +356,8 @@ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
 
 	for (i = 0; i < tagset->nr_hw_queues; i++) {
 		if (tagset->tags && tagset->tags[i])
-			blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv);
+			blk_mq_all_tag_busy_iter(tagset->tags[i], fn,
+					blk_mq_default_busy_rq, priv);
 	}
 }
 EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index 2b8321efb682..fdf095d513e5 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -21,6 +21,7 @@ struct blk_mq_tags {
 	struct list_head page_list;
 };
 
+typedef bool (busy_rq_iter_fn)(struct request *, void *, bool);
 
 extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node, int alloc_policy);
 extern void blk_mq_free_tags(struct blk_mq_tags *tags);
@@ -34,6 +35,9 @@ extern int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool);
 void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
 		void *priv);
+void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
+		busy_tag_iter_fn *fn, busy_rq_iter_fn *busy_rq_fn,
+		void *priv);
 
 static inline struct sbq_wait_state *bt_wait_ptr(struct sbitmap_queue *bt,
 						 struct blk_mq_hw_ctx *hctx)
-- 
2.25.2