[V11,05/12] blk-mq: add blk_mq_all_tag_iter

Commit Message

Ming Lei May 13, 2020, 3:47 a.m. UTC

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

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

Add one new function of blk_mq_all_tag_iter so that we can iterate
every in-flight request, and this way is more flexible since caller
can decide to handle request according to rq's state.

Cc: Bart Van Assche <[e-mail]>
Cc: Hannes Reinecke <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: John Garry <[e-mail]>
Signed-off-by: Ming Lei <[e-mail]>
---
 block/blk-mq-tag.c | 33 +++++++++++++++++++++++++++++----
 block/blk-mq-tag.h |  2 ++
 2 files changed, 31 insertions(+), 4 deletions(-)

Comments

Christoph Hellwig May 13, 2020, 11:56 a.m. UTC | #1

On Wed, May 13, 2020 at 11:47:56AM +0800, Ming Lei wrote:
> Now request is thought as in-flight only when its state is updated as
> MQ_RQ_IN_FLIGHT, which is done by driver via blk_mq_start_request().

This should probably mention who considers it it in flight.

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

> Add one new function of blk_mq_all_tag_iter so that we can iterate
> every in-flight request, and this way is more flexible since caller
> can decide to handle request according to rq's state.

Maybe I'd reword the whole commit log as:

"Add a new blk_mq_all_tag_iter that iterates all requets which have a tag
assigned to them.  This is more flexible than the existing iterator
iterator as it allows the caller to check the request state and act
upon it."

Otherwise looks good:

Reviewed-by: Christoph Hellwig <[e-mail]>

Patch

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 586c9d6e904a..c27c6dfc7d36 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -257,6 +257,7 @@  struct bt_tags_iter_data {
 	busy_tag_iter_fn *fn;
 	void *data;
 	bool reserved;
+	bool iterate_all;
 };
 
 static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
@@ -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->iterate_all || blk_mq_request_started(rq)))
 		return iter_data->fn(rq, iter_data->data, reserved);
 
 	return true;
@@ -294,13 +295,15 @@  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, void *data, bool reserved,
+			     bool iterate_all)
 {
 	struct bt_tags_iter_data iter_data = {
 		.tags = tags,
 		.fn = fn,
 		.data = data,
 		.reserved = reserved,
+		.iterate_all = iterate_all,
 	};
 
 	if (tags->rqs)
@@ -321,8 +324,30 @@  static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
 		busy_tag_iter_fn *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, priv, true,
+				 false);
+	bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false, false);
+}
+
+/**
+ * blk_mq_all_tag_iter - iterate over all requests in a tag map
+ * @tags:	Tag map to iterate over.
+ * @fn:		Pointer to the function that will be called for each
+ *		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.
+ * @priv:	Will be passed as second argument to @fn.
+ *
+ * It is the caller's responsibility to check rq's state in @fn.
+ */
+void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
+		void *priv)
+{
+	if (tags->nr_reserved_tags)
+		bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true,
+				 true);
+	bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false, true);
 }
 
 /**
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index 2b8321efb682..d19546e8246b 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -34,6 +34,8 @@  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_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
+		void *priv);
 
 static inline struct sbq_wait_state *bt_wait_ptr(struct sbitmap_queue *bt,
 						 struct blk_mq_hw_ctx *hctx)