[PATCH 03/10] xen/blkfront: reorg info->io_lock after using blk-mq API

From: Bob Liu <bob.liu@oracle.com>
To: xen-devel@lists.xen.org
Cc: david.vrabel@citrix.com, linux-kernel@vger.kernel.org,
	roger.pau@citrix.com, konrad.wilk@oracle.com,
	felipe.franciosi@citrix.com, axboe@fb.com, hch@infradead.org,
	avanzini.arianna@gmail.com, Bob Liu <bob.liu@oracle.com>
Subject: [PATCH 03/10] xen/blkfront: reorg info->io_lock after using blk-mq API
Date: Sun, 15 Feb 2015 16:18:58 +0800	[thread overview]
Message-ID: <1423988345-4005-4-git-send-email-bob.liu@oracle.com> (raw)
In-Reply-To: <1423988345-4005-1-git-send-email-bob.liu@oracle.com>

Drop unnecessary holding of info->io_lock when calling into blk-mq apis.

Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
 drivers/block/xen-blkfront.c | 38 ++++++++++++++++----------------------
 1 file changed, 16 insertions(+), 22 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 3589436..5a90a51 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -614,25 +614,28 @@ static int blk_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
 	blk_mq_start_request(qd->rq);
 	spin_lock_irq(&info->io_lock);
 	if (RING_FULL(&info->ring)) {
+		spin_unlock_irq(&info->io_lock);
 		blk_mq_stop_hw_queue(hctx);
 		ret = BLK_MQ_RQ_QUEUE_BUSY;
 		goto out;
 	}
 
 	if (blkif_request_flush_invalid(qd->rq, info)) {
+		spin_unlock_irq(&info->io_lock);
 		ret = BLK_MQ_RQ_QUEUE_ERROR;
 		goto out;
 	}
 
 	if (blkif_queue_request(qd->rq)) {
+		spin_unlock_irq(&info->io_lock);
 		blk_mq_stop_hw_queue(hctx);
 		ret = BLK_MQ_RQ_QUEUE_BUSY;
 		goto out;
 	}
 
 	flush_requests(info);
-out:
 	spin_unlock_irq(&info->io_lock);
+out:
 	return ret;
 }
 
@@ -891,19 +894,15 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
 static void xlvbd_release_gendisk(struct blkfront_info *info)
 {
 	unsigned int minor, nr_minors;
-	unsigned long flags;
 
 	if (info->rq == NULL)
 		return;
 
-	spin_lock_irqsave(&info->io_lock, flags);
-
 	/* No more blkif_request(). */
 	blk_mq_stop_hw_queues(info->rq);
 
 	/* No more gnttab callback work. */
 	gnttab_cancel_free_callback(&info->callback);
-	spin_unlock_irqrestore(&info->io_lock, flags);
 
 	/* Flush gnttab callback work. Must be done with no locks held. */
 	flush_work(&info->work);
@@ -922,21 +921,25 @@ static void xlvbd_release_gendisk(struct blkfront_info *info)
 	info->gd = NULL;
 }
 
-/* Called with info->io_lock holded */
 static void kick_pending_request_queues(struct blkfront_info *info)
 {
-	if (!RING_FULL(&info->ring))
+	unsigned long flags;
+
+	spin_lock_irqsave(&info->io_lock, flags);
+	if (!RING_FULL(&info->ring)) {
+		spin_unlock_irqrestore(&info->io_lock, flags);
 		blk_mq_start_stopped_hw_queues(info->rq, true);
+		return;
+	}
+	spin_unlock_irqrestore(&info->io_lock, flags);
 }
 
 static void blkif_restart_queue(struct work_struct *work)
 {
 	struct blkfront_info *info = container_of(work, struct blkfront_info, work);
 
-	spin_lock_irq(&info->io_lock);
 	if (info->connected == BLKIF_STATE_CONNECTED)
 		kick_pending_request_queues(info);
-	spin_unlock_irq(&info->io_lock);
 }
 
 static void blkif_free(struct blkfront_info *info, int suspend)
@@ -946,13 +949,13 @@ static void blkif_free(struct blkfront_info *info, int suspend)
 	int i, j, segs;
 
 	/* Prevent new requests being issued until we fix things up. */
-	spin_lock_irq(&info->io_lock);
 	info->connected = suspend ?
 		BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED;
 	/* No more blkif_request(). */
 	if (info->rq)
 		blk_mq_stop_hw_queues(info->rq);
 
+	spin_lock_irq(&info->io_lock);
 	/* Remove all persistent grants */
 	if (!list_empty(&info->grants)) {
 		list_for_each_entry_safe(persistent_gnt, n,
@@ -1136,13 +1139,10 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 	unsigned long flags;
 	struct blkfront_info *info = (struct blkfront_info *)dev_id;
 
-	spin_lock_irqsave(&info->io_lock, flags);
-
-	if (unlikely(info->connected != BLKIF_STATE_CONNECTED)) {
-		spin_unlock_irqrestore(&info->io_lock, flags);
+	if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
 		return IRQ_HANDLED;
-	}
 
+	spin_lock_irqsave(&info->io_lock, flags);
  again:
 	rp = info->ring.sring->rsp_prod;
 	rmb(); /* Ensure we see queued responses up to 'rp'. */
@@ -1233,9 +1233,8 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 	} else
 		info->ring.sring->rsp_event = i + 1;
 
-	kick_pending_request_queues(info);
-
 	spin_unlock_irqrestore(&info->io_lock, flags);
+	kick_pending_request_queues(info);
 
 	return IRQ_HANDLED;
 }
@@ -1518,8 +1517,6 @@ static int blkif_recover(struct blkfront_info *info)
 
 	xenbus_switch_state(info->xbdev, XenbusStateConnected);
 
-	spin_lock_irq(&info->io_lock);
-
 	/* Now safe for us to use the shared ring */
 	info->connected = BLKIF_STATE_CONNECTED;
 
@@ -1533,7 +1530,6 @@ static int blkif_recover(struct blkfront_info *info)
 		blk_mq_requeue_request(req);
 	}
 	blk_mq_kick_requeue_list(info->rq);
-	spin_unlock_irq(&info->io_lock);
 
 	while ((bio = bio_list_pop(&bio_list)) != NULL) {
 		/* Traverse the list of pending bios and re-queue them */
@@ -1863,10 +1859,8 @@ static void blkfront_connect(struct blkfront_info *info)
 	xenbus_switch_state(info->xbdev, XenbusStateConnected);
 
 	/* Kick pending requests. */
-	spin_lock_irq(&info->io_lock);
 	info->connected = BLKIF_STATE_CONNECTED;
 	kick_pending_request_queues(info);
-	spin_unlock_irq(&info->io_lock);
 
 	add_disk(info->gd);
 
-- 
1.8.3.1

