drivers: xen-blkback: delay pending_req allocation to connect_ring

This is a pre-patch for multi-page ring feature.
In connect_ring, we can know exactly how many pages are used for the shared
ring, delay pending_req allocation here so that we won't waste too much memory.

Signed-off-by: Bob Liu <bob.liu@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

2 files changed, 39 insertions, 45 deletions

diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index f620b5d3f77c..043f13b7b7b0 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -248,7 +248,7 @@ struct backend_info;
 #define PERSISTENT_GNT_WAS_ACTIVE       1
 
 /* Number of requests that we can fit in a ring */
-#define XEN_BLKIF_REQS                  32
+#define XEN_BLKIF_REQS_PER_PAGE         32
 
 struct persistent_gnt {
         struct page *page;
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 6ab69ad61ee1..c212d41fd5bd 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -124,8 +124,6 @@ static void xen_update_blkif_status(struct xen_blkif *blkif)
 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 {
         struct xen_blkif *blkif;
-        struct pending_req *req, *n;
-        int i, j;
 
         BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 
@@ -151,51 +149,11 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 
         INIT_LIST_HEAD(&blkif->pending_free);
         INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
-
-        for (i = 0; i < XEN_BLKIF_REQS; i++) {
-                req = kzalloc(sizeof(*req), GFP_KERNEL);
-                if (!req)
-                        goto fail;
-                list_add_tail(&req->free_list,
-                              &blkif->pending_free);
-                for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
-                        req->segments[j] = kzalloc(sizeof(*req->segments[0]),
-                                                   GFP_KERNEL);
-                        if (!req->segments[j])
-                                goto fail;
-                }
-                for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
-                        req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
-                                                         GFP_KERNEL);
-                        if (!req->indirect_pages[j])
-                                goto fail;
-                }
-        }
         spin_lock_init(&blkif->pending_free_lock);
         init_waitqueue_head(&blkif->pending_free_wq);
         init_waitqueue_head(&blkif->shutdown_wq);
 
         return blkif;
-
-fail:
-        list_for_each_entry_safe(req, n, &blkif->pending_free, free_list) {
-                list_del(&req->free_list);
-                for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
-                        if (!req->segments[j])
-                                break;
-                        kfree(req->segments[j]);
-                }
-                for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
-                        if (!req->indirect_pages[j])
-                                break;
-                        kfree(req->indirect_pages[j]);
-                }
-                kfree(req);
-        }
-
-        kmem_cache_free(xen_blkif_cachep, blkif);
-
-        return ERR_PTR(-ENOMEM);
 }
 
 static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t gref,
@@ -312,7 +270,7 @@ static void xen_blkif_free(struct xen_blkif *blkif)
                 i++;
         }
 
-        WARN_ON(i != XEN_BLKIF_REQS);
+        WARN_ON(i != XEN_BLKIF_REQS_PER_PAGE);
 
         kmem_cache_free(xen_blkif_cachep, blkif);
 }
@@ -864,7 +822,8 @@ static int connect_ring(struct backend_info *be)
         unsigned int evtchn;
         unsigned int pers_grants;
         char protocol[64] = "";
-        int err;
+        struct pending_req *req, *n;
+        int err, i, j;
 
         pr_debug("%s %s\n", __func__, dev->otherend);
 
@@ -905,6 +864,24 @@ static int connect_ring(struct backend_info *be)
                 ring_ref, evtchn, be->blkif->blk_protocol, protocol,
                 pers_grants ? "persistent grants" : "");
 
+        for (i = 0; i < XEN_BLKIF_REQS_PER_PAGE; i++) {
+                req = kzalloc(sizeof(*req), GFP_KERNEL);
+                if (!req)
+                        goto fail;
+                list_add_tail(&req->free_list, &be->blkif->pending_free);
+                for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
+                        req->segments[j] = kzalloc(sizeof(*req->segments[0]), GFP_KERNEL);
+                        if (!req->segments[j])
+                                goto fail;
+                }
+                for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
+                        req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
+                                                         GFP_KERNEL);
+                        if (!req->indirect_pages[j])
+                                goto fail;
+                }
+        }
+
         /* Map the shared frame, irq etc. */
         err = xen_blkif_map(be->blkif, ring_ref, evtchn);
         if (err) {
@@ -914,6 +891,23 @@ static int connect_ring(struct backend_info *be)
         }
 
         return 0;
+
+fail:
+        list_for_each_entry_safe(req, n, &be->blkif->pending_free, free_list) {
+                list_del(&req->free_list);
+                for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
+                        if (!req->segments[j])
+                                break;
+                        kfree(req->segments[j]);
+                }
+                for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
+                        if (!req->indirect_pages[j])
+                                break;
+                        kfree(req->indirect_pages[j]);
+                }
+                kfree(req);
+        }
+        return -ENOMEM;
 }
 
 static const struct xenbus_device_id xen_blkbk_ids[] = {