xen-blkback: make the queue of free requests per backend

Remove the last dependency from blkbk by moving the list of free
requests to blkif. This change reduces the contention on the list of
available requests.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: xen-devel@lists.xen.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index e0fd92a2a4cd..1f1ade6d6e09 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -105,6 +105,7 @@ static void xen_update_blkif_status(struct xen_blkif *blkif)
 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 {
 	struct xen_blkif *blkif;
+	int i;
 
 	blkif = kmem_cache_zalloc(xen_blkif_cachep, GFP_KERNEL);
 	if (!blkif)
@@ -124,6 +125,21 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 	blkif->free_pages_num = 0;
 	atomic_set(&blkif->persistent_gnt_in_use, 0);
 
+	blkif->pending_reqs = kcalloc(XEN_BLKIF_REQS,
+	                              sizeof(blkif->pending_reqs[0]),
+	                              GFP_KERNEL);
+	if (!blkif->pending_reqs) {
+		kmem_cache_free(xen_blkif_cachep, blkif);
+		return ERR_PTR(-ENOMEM);
+	}
+	INIT_LIST_HEAD(&blkif->pending_free);
+	spin_lock_init(&blkif->pending_free_lock);
+	init_waitqueue_head(&blkif->pending_free_wq);
+
+	for (i = 0; i < XEN_BLKIF_REQS; i++)
+		list_add_tail(&blkif->pending_reqs[i].free_list,
+			      &blkif->pending_free);
+
 	return blkif;
 }
 
@@ -203,8 +219,18 @@ static void xen_blkif_disconnect(struct xen_blkif *blkif)
 
 static void xen_blkif_free(struct xen_blkif *blkif)
 {
+	struct pending_req *req;
+	int i = 0;
+
 	if (!atomic_dec_and_test(&blkif->refcnt))
 		BUG();
+
+	/* Check that there is no request in use */
+	list_for_each_entry(req, &blkif->pending_free, free_list)
+		i++;
+	BUG_ON(i != XEN_BLKIF_REQS);
+
+	kfree(blkif->pending_reqs);
 	kmem_cache_free(xen_blkif_cachep, blkif);
 }