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

[Bob Liu <bob.liu@xxxxxxxxxx>]

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

Signed-off-by: Bob Liu <bob.liu@xxxxxxxxxx>
---
 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


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