xen-blkfront: make blkif_io_lock spinlock per-device
This patch moves the global blkif_io_lock to the per-device structure. The
spinlock seems to exists for two reasons: to disable IRQs when in the interrupt
handlers for blkfront, and to protect the blkfront VBDs when a detachment is
requested.
Having a global blkif_io_lock doesn't make sense given the use case, and it
drastically hinders performance due to contention. All VBDs with pending IOs
have to take the lock in order to get work done, which serializes everything
pretty badly.
Signed-off-by: Steven Noonan <snoonan@amazon.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 537cb72..5d9c559 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -82,6 +82,7 @@
*/
struct blkfront_info
{
+ spinlock_t io_lock;
struct mutex mutex;
struct xenbus_device *xbdev;
struct gendisk *gd;
@@ -106,8 +107,6 @@
int is_ready;
};
-static DEFINE_SPINLOCK(blkif_io_lock);
-
static unsigned int nr_minors;
static unsigned long *minors;
static DEFINE_SPINLOCK(minor_lock);
@@ -418,7 +417,7 @@
struct request_queue *rq;
struct blkfront_info *info = gd->private_data;
- rq = blk_init_queue(do_blkif_request, &blkif_io_lock);
+ rq = blk_init_queue(do_blkif_request, &info->io_lock);
if (rq == NULL)
return -1;
@@ -635,14 +634,14 @@
if (info->rq == NULL)
return;
- spin_lock_irqsave(&blkif_io_lock, flags);
+ spin_lock_irqsave(&info->io_lock, flags);
/* No more blkif_request(). */
blk_stop_queue(info->rq);
/* No more gnttab callback work. */
gnttab_cancel_free_callback(&info->callback);
- spin_unlock_irqrestore(&blkif_io_lock, flags);
+ spin_unlock_irqrestore(&info->io_lock, flags);
/* Flush gnttab callback work. Must be done with no locks held. */
flush_work_sync(&info->work);
@@ -674,16 +673,16 @@
{
struct blkfront_info *info = container_of(work, struct blkfront_info, work);
- spin_lock_irq(&blkif_io_lock);
+ spin_lock_irq(&info->io_lock);
if (info->connected == BLKIF_STATE_CONNECTED)
kick_pending_request_queues(info);
- spin_unlock_irq(&blkif_io_lock);
+ spin_unlock_irq(&info->io_lock);
}
static void blkif_free(struct blkfront_info *info, int suspend)
{
/* Prevent new requests being issued until we fix things up. */
- spin_lock_irq(&blkif_io_lock);
+ spin_lock_irq(&info->io_lock);
info->connected = suspend ?
BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED;
/* No more blkif_request(). */
@@ -691,7 +690,7 @@
blk_stop_queue(info->rq);
/* No more gnttab callback work. */
gnttab_cancel_free_callback(&info->callback);
- spin_unlock_irq(&blkif_io_lock);
+ spin_unlock_irq(&info->io_lock);
/* Flush gnttab callback work. Must be done with no locks held. */
flush_work_sync(&info->work);
@@ -727,10 +726,10 @@
struct blkfront_info *info = (struct blkfront_info *)dev_id;
int error;
- spin_lock_irqsave(&blkif_io_lock, flags);
+ spin_lock_irqsave(&info->io_lock, flags);
if (unlikely(info->connected != BLKIF_STATE_CONNECTED)) {
- spin_unlock_irqrestore(&blkif_io_lock, flags);
+ spin_unlock_irqrestore(&info->io_lock, flags);
return IRQ_HANDLED;
}
@@ -815,7 +814,7 @@
kick_pending_request_queues(info);
- spin_unlock_irqrestore(&blkif_io_lock, flags);
+ spin_unlock_irqrestore(&info->io_lock, flags);
return IRQ_HANDLED;
}
@@ -990,6 +989,7 @@
}
mutex_init(&info->mutex);
+ spin_lock_init(&info->io_lock);
info->xbdev = dev;
info->vdevice = vdevice;
info->connected = BLKIF_STATE_DISCONNECTED;
@@ -1067,7 +1067,7 @@
xenbus_switch_state(info->xbdev, XenbusStateConnected);
- spin_lock_irq(&blkif_io_lock);
+ spin_lock_irq(&info->io_lock);
/* Now safe for us to use the shared ring */
info->connected = BLKIF_STATE_CONNECTED;
@@ -1078,7 +1078,7 @@
/* Kick any other new requests queued since we resumed */
kick_pending_request_queues(info);
- spin_unlock_irq(&blkif_io_lock);
+ spin_unlock_irq(&info->io_lock);
return 0;
}
@@ -1276,10 +1276,10 @@
xenbus_switch_state(info->xbdev, XenbusStateConnected);
/* Kick pending requests. */
- spin_lock_irq(&blkif_io_lock);
+ spin_lock_irq(&info->io_lock);
info->connected = BLKIF_STATE_CONNECTED;
kick_pending_request_queues(info);
- spin_unlock_irq(&blkif_io_lock);
+ spin_unlock_irq(&info->io_lock);
add_disk(info->gd);