xen/blkfront: split per device io_lock
After patch "xen/blkfront: separate per ring information out of device
info", per-ring data is protected by a per-device lock ('io_lock').
This is not a good way and will effect the scalability, so introduce a
per-ring lock ('ring_lock').
The old 'io_lock' is renamed to 'dev_lock' which protects the ->grants list and
->persistent_gnts_c which are shared by all rings.
Note that in 'blkfront_probe' the 'blkfront_info' is setup via kzalloc
so setting ->persistent_gnts_c to zero is not needed.
Signed-off-by: Bob Liu <bob.liu@oracle.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 0638b17..a9058bb 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -125,6 +125,8 @@
* depending on how many hardware queues/rings to be used.
*/
struct blkfront_ring_info {
+ /* Lock to protect data in every ring buffer. */
+ spinlock_t ring_lock;
struct blkif_front_ring ring;
unsigned int ring_ref[XENBUS_MAX_RING_GRANTS];
unsigned int evtchn, irq;
@@ -143,7 +145,6 @@
*/
struct blkfront_info
{
- spinlock_t io_lock;
struct mutex mutex;
struct xenbus_device *xbdev;
struct gendisk *gd;
@@ -153,6 +154,11 @@
/* Number of pages per ring buffer. */
unsigned int nr_ring_pages;
struct request_queue *rq;
+ /*
+ * Lock to protect info->grants list and persistent_gnts_c shared by all
+ * rings.
+ */
+ spinlock_t dev_lock;
struct list_head grants;
unsigned int persistent_gnts_c;
unsigned int feature_flush;
@@ -258,7 +264,9 @@
}
gnt_list_entry->gref = GRANT_INVALID_REF;
+ spin_lock_irq(&info->dev_lock);
list_add(&gnt_list_entry->node, &info->grants);
+ spin_unlock_irq(&info->dev_lock);
i++;
}
@@ -267,7 +275,9 @@
out_of_memory:
list_for_each_entry_safe(gnt_list_entry, n,
&info->grants, node) {
+ spin_lock_irq(&info->dev_lock);
list_del(&gnt_list_entry->node);
+ spin_unlock_irq(&info->dev_lock);
if (info->feature_persistent)
__free_page(gnt_list_entry->page);
kfree(gnt_list_entry);
@@ -280,7 +290,9 @@
static struct grant *get_free_grant(struct blkfront_info *info)
{
struct grant *gnt_list_entry;
+ unsigned long flags;
+ spin_lock_irqsave(&info->dev_lock, flags);
BUG_ON(list_empty(&info->grants));
gnt_list_entry = list_first_entry(&info->grants, struct grant,
node);
@@ -288,6 +300,7 @@
if (gnt_list_entry->gref != GRANT_INVALID_REF)
info->persistent_gnts_c--;
+ spin_unlock_irqrestore(&info->dev_lock, flags);
return gnt_list_entry;
}
@@ -757,11 +770,11 @@
static int blkif_queue_rq(struct blk_mq_hw_ctx *hctx,
const struct blk_mq_queue_data *qd)
{
+ unsigned long flags;
struct blkfront_ring_info *rinfo = (struct blkfront_ring_info *)hctx->driver_data;
- struct blkfront_info *info = rinfo->dev_info;
blk_mq_start_request(qd->rq);
- spin_lock_irq(&info->io_lock);
+ spin_lock_irqsave(&rinfo->ring_lock, flags);
if (RING_FULL(&rinfo->ring))
goto out_busy;
@@ -772,15 +785,15 @@
goto out_busy;
flush_requests(rinfo);
- spin_unlock_irq(&info->io_lock);
+ spin_unlock_irqrestore(&rinfo->ring_lock, flags);
return BLK_MQ_RQ_QUEUE_OK;
out_err:
- spin_unlock_irq(&info->io_lock);
+ spin_unlock_irqrestore(&rinfo->ring_lock, flags);
return BLK_MQ_RQ_QUEUE_ERROR;
out_busy:
- spin_unlock_irq(&info->io_lock);
+ spin_unlock_irqrestore(&rinfo->ring_lock, flags);
blk_mq_stop_hw_queue(hctx);
return BLK_MQ_RQ_QUEUE_BUSY;
}
@@ -1082,21 +1095,28 @@
info->gd = NULL;
}
-/* Must be called with io_lock holded */
-static void kick_pending_request_queues(struct blkfront_ring_info *rinfo)
+/* Already hold rinfo->ring_lock. */
+static inline void kick_pending_request_queues_locked(struct blkfront_ring_info *rinfo)
{
if (!RING_FULL(&rinfo->ring))
blk_mq_start_stopped_hw_queues(rinfo->dev_info->rq, true);
}
+static void kick_pending_request_queues(struct blkfront_ring_info *rinfo)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&rinfo->ring_lock, flags);
+ kick_pending_request_queues_locked(rinfo);
+ spin_unlock_irqrestore(&rinfo->ring_lock, flags);
+}
+
static void blkif_restart_queue(struct work_struct *work)
{
struct blkfront_ring_info *rinfo = container_of(work, struct blkfront_ring_info, work);
- spin_lock_irq(&rinfo->dev_info->io_lock);
if (rinfo->dev_info->connected == BLKIF_STATE_CONNECTED)
kick_pending_request_queues(rinfo);
- spin_unlock_irq(&rinfo->dev_info->io_lock);
}
static void blkif_free_ring(struct blkfront_ring_info *rinfo)
@@ -1188,7 +1208,6 @@
unsigned int i;
/* 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(). */
@@ -1196,6 +1215,7 @@
blk_mq_stop_hw_queues(info->rq);
/* Remove all persistent grants */
+ spin_lock_irq(&info->dev_lock);
if (!list_empty(&info->grants)) {
list_for_each_entry_safe(persistent_gnt, n,
&info->grants, node) {
@@ -1211,6 +1231,7 @@
}
}
BUG_ON(info->persistent_gnts_c != 0);
+ spin_unlock_irq(&info->dev_lock);
for (i = 0; i < info->nr_rings; i++)
blkif_free_ring(&info->rinfo[i]);
@@ -1218,7 +1239,6 @@
kfree(info->rinfo);
info->rinfo = NULL;
info->nr_rings = 0;
- spin_unlock_irq(&info->io_lock);
}
struct copy_from_grant {
@@ -1253,6 +1273,7 @@
int i = 0;
struct scatterlist *sg;
int num_sg, num_grant;
+ unsigned long flags;
struct blkfront_info *info = rinfo->dev_info;
struct copy_from_grant data = {
.s = s,
@@ -1291,8 +1312,10 @@
if (!info->feature_persistent)
pr_alert_ratelimited("backed has not unmapped grant: %u\n",
s->grants_used[i]->gref);
+ spin_lock_irqsave(&info->dev_lock, flags);
list_add(&s->grants_used[i]->node, &info->grants);
info->persistent_gnts_c++;
+ spin_unlock_irqrestore(&info->dev_lock, flags);
} else {
/*
* If the grant is not mapped by the backend we end the
@@ -1302,7 +1325,9 @@
*/
gnttab_end_foreign_access(s->grants_used[i]->gref, 0, 0UL);
s->grants_used[i]->gref = GRANT_INVALID_REF;
+ spin_lock_irqsave(&info->dev_lock, flags);
list_add_tail(&s->grants_used[i]->node, &info->grants);
+ spin_unlock_irqrestore(&info->dev_lock, flags);
}
}
if (s->req.operation == BLKIF_OP_INDIRECT) {
@@ -1311,8 +1336,10 @@
if (!info->feature_persistent)
pr_alert_ratelimited("backed has not unmapped grant: %u\n",
s->indirect_grants[i]->gref);
+ spin_lock_irqsave(&info->dev_lock, flags);
list_add(&s->indirect_grants[i]->node, &info->grants);
info->persistent_gnts_c++;
+ spin_unlock_irqrestore(&info->dev_lock, flags);
} else {
struct page *indirect_page;
@@ -1326,7 +1353,9 @@
list_add(&indirect_page->lru, &rinfo->indirect_pages);
}
s->indirect_grants[i]->gref = GRANT_INVALID_REF;
+ spin_lock_irqsave(&info->dev_lock, flags);
list_add_tail(&s->indirect_grants[i]->node, &info->grants);
+ spin_unlock_irqrestore(&info->dev_lock, flags);
}
}
}
@@ -1342,13 +1371,10 @@
struct blkfront_info *info = rinfo->dev_info;
int error;
- 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(&rinfo->ring_lock, flags);
again:
rp = rinfo->ring.sring->rsp_prod;
rmb(); /* Ensure we see queued responses up to 'rp'. */
@@ -1439,9 +1465,9 @@
} else
rinfo->ring.sring->rsp_event = i + 1;
- kick_pending_request_queues(rinfo);
+ kick_pending_request_queues_locked(rinfo);
- spin_unlock_irqrestore(&info->io_lock, flags);
+ spin_unlock_irqrestore(&rinfo->ring_lock, flags);
return IRQ_HANDLED;
}
@@ -1690,14 +1716,14 @@
INIT_LIST_HEAD(&rinfo->indirect_pages);
rinfo->dev_info = info;
INIT_WORK(&rinfo->work, blkif_restart_queue);
+ spin_lock_init(&rinfo->ring_lock);
}
mutex_init(&info->mutex);
- spin_lock_init(&info->io_lock);
+ spin_lock_init(&info->dev_lock);
info->xbdev = dev;
info->vdevice = vdevice;
INIT_LIST_HEAD(&info->grants);
- info->persistent_gnts_c = 0;
info->connected = BLKIF_STATE_DISCONNECTED;
/* Front end dir is a number, which is used as the id. */
@@ -1790,8 +1816,6 @@
}
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;
@@ -1809,7 +1833,6 @@
BUG_ON(req->nr_phys_segments > segs);
blk_mq_requeue_request(req);
}
- spin_unlock_irq(&info->io_lock);
blk_mq_kick_requeue_list(info->rq);
while ((bio = bio_list_pop(&bio_list)) != NULL) {
@@ -2158,11 +2181,9 @@
xenbus_switch_state(info->xbdev, XenbusStateConnected);
/* Kick pending requests. */
- spin_lock_irq(&info->io_lock);
info->connected = BLKIF_STATE_CONNECTED;
for (i = 0; i < info->nr_rings; i++)
kick_pending_request_queues(&info->rinfo[i]);
- spin_unlock_irq(&info->io_lock);
add_disk(info->gd);