block: skip elevator data initialization for flush requests

Skip elevator initialization for flush requests by passing priv=0 to blk_alloc_request() in get_request(). As such elv_set_request() is never called for flush requests. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

block: skip elevator data initialization for flush requests
Skip elevator initialization for flush requests by passing priv=0 to blk_alloc_request() in get_request(). As such elv_set_request() is never called for flush requests. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Mike Snitzer · Jens Axboe
1 parent ae1b153962
Showing 1 changed file with 25 additions and 4 deletions Side-by-side Diff
block/blk-core.c
@@ -738,6 +738,25 @@
 }
  
 /*
+ * Determine if elevator data should be initialized when allocating the
+ * request associated with @bio.
+ */
+static bool blk_rq_should_init_elevator(struct bio *bio)
+{
+	if (!bio)
+		return true;
+
+	/*
+	 * Flush requests do not use the elevator so skip initialization.
+	 * This allows a request to share the flush and elevator data.
+	 */
+	if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
+		return false;
+
+	return true;
+}
+
+/*
  * Get a free request, queue_lock must be held.
  * Returns NULL on failure, with queue_lock held.
  * Returns !NULL on success, with queue_lock *not held*.
@@ -749,7 +768,7 @@
 	struct request_list *rl = &q->rq;
 	struct io_context *ioc = NULL;
 	const bool is_sync = rw_is_sync(rw_flags) != 0;
-	int may_queue, priv;
+	int may_queue, priv = 0;
  
 	may_queue = elv_may_queue(q, rw_flags);
 	if (may_queue == ELV_MQUEUE_NO)
@@ -793,9 +812,11 @@
 	rl->count[is_sync]++;
 	rl->starved[is_sync] = 0;
  
-	priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
-	if (priv)
-		rl->elvpriv++;
+	if (blk_rq_should_init_elevator(bio)) {
+		priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
+		if (priv)
+			rl->elvpriv++;
+	}
  
 	if (blk_queue_io_stat(q))
 		rw_flags |= REQ_IO_STAT;
...	...	@@ -738,6 +738,25 @@
738	738	}
739	739
740	740	/*
	741	+ * Determine if elevator data should be initialized when allocating the
	742	+ * request associated with @bio.
	743	+ */
	744	+static bool blk_rq_should_init_elevator(struct bio *bio)
	745	+{
	746	+ if (!bio)
	747	+ return true;
	748	+
	749	+ /*
	750	+ * Flush requests do not use the elevator so skip initialization.
	751	+ * This allows a request to share the flush and elevator data.
	752	+ */
	753	+ if (bio->bi_rw & (REQ_FLUSH \| REQ_FUA))
	754	+ return false;
	755	+
	756	+ return true;
	757	+}
	758	+
	759	+/*
741	760	* Get a free request, queue_lock must be held.
742	761	* Returns NULL on failure, with queue_lock held.
743	762	* Returns !NULL on success, with queue_lock not held.
...	...	@@ -749,7 +768,7 @@
749	768	struct request_list *rl = &q->rq;
750	769	struct io_context *ioc = NULL;
751	770	const bool is_sync = rw_is_sync(rw_flags) != 0;
752		- int may_queue, priv;
	771	+ int may_queue, priv = 0;
753	772
754	773	may_queue = elv_may_queue(q, rw_flags);
755	774	if (may_queue == ELV_MQUEUE_NO)
...	...	@@ -793,9 +812,11 @@
793	812	rl->count[is_sync]++;
794	813	rl->starved[is_sync] = 0;
795	814
796		- priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
797		- if (priv)
798		- rl->elvpriv++;
	815	+ if (blk_rq_should_init_elevator(bio)) {
	816	+ priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
	817	+ if (priv)
	818	+ rl->elvpriv++;
	819	+ }
799	820
800	821	if (blk_queue_io_stat(q))
801	822	rw_flags \|= REQ_IO_STAT;