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 (file)
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -125,6 +125,8 @@ MODULE_PARM_DESC(max_ring_page_order, "Maximum order of pages to be used for the
  *  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_ring_info {
  */
 struct blkfront_info
 {
-       spinlock_t io_lock;
        struct mutex mutex;
        struct xenbus_device *xbdev;
        struct gendisk *gd;
@@ -153,6 +154,11 @@ struct blkfront_info
        /* 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 @@ static int fill_grant_buffer(struct blkfront_ring_info *rinfo, int num)
                }
 
                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 @@ static int fill_grant_buffer(struct blkfront_ring_info *rinfo, int num)
 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 @@ out_of_memory:
 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 @@ static struct grant *get_free_grant(struct blkfront_info *info)
 
        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 inline bool blkif_request_flush_invalid(struct request *req,
 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 @@ static int blkif_queue_rq(struct blk_mq_hw_ctx *hctx,
                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 @@ static void xlvbd_release_gendisk(struct blkfront_info *info)
        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 @@ static void blkif_free(struct blkfront_info *info, int suspend)
        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 @@ static void blkif_free(struct blkfront_info *info, int suspend)
                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 @@ static void blkif_free(struct blkfront_info *info, int suspend)
                }
        }
        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 @@ static void blkif_free(struct blkfront_info *info, int suspend)
        kfree(info->rinfo);
        info->rinfo = NULL;
        info->nr_rings = 0;
-       spin_unlock_irq(&info->io_lock);
 }
 
 struct copy_from_grant {
@@ -1253,6 +1273,7 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_ring_info *ri
        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 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_ring_info *ri
                        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 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_ring_info *ri
                         */
                        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 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_ring_info *ri
                                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 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_ring_info *ri
                                        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 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
        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 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
        } 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 @@ static int blkfront_probe(struct xenbus_device *dev,
                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 @@ 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;
 
@@ -1809,7 +1833,6 @@ static int blkif_recover(struct blkfront_info *info)
                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 @@ 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;
        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);