xen-blkback: don't store dev_bus_addr

dev_bus_addr returned in the grant ref map operation is the mfn of the
passed page, there's no need to store it in the persistent grant
entry, since we can always get it provided that we have the page.

This reduces the memory overhead of persistent grants in blkback.

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

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 477a17c20820d74422f7549106a3e583df838a40..d909acf00113ceed2da332b504d4eece87759c53 100644 (file)
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -621,30 +621,21 @@ static int xen_blkbk_map(struct blkif_request *req,
                                 * If this is a new persistent grant
                                 * save the handler
                                 */
-                               persistent_gnts[i]->handle = map[j].handle;
-                               persistent_gnts[i]->dev_bus_addr =
-                                       map[j++].dev_bus_addr;
+                               persistent_gnts[i]->handle = map[j++].handle;
                        }
                        pending_handle(pending_req, i) =
                                persistent_gnts[i]->handle;
 
                        if (ret)
                                continue;
-
-                       seg[i].buf = persistent_gnts[i]->dev_bus_addr |
-                               (req->u.rw.seg[i].first_sect << 9);
                } else {
-                       pending_handle(pending_req, i) = map[j].handle;
+                       pending_handle(pending_req, i) = map[j++].handle;
                        bitmap_set(pending_req->unmap_seg, i, 1);
 
-                       if (ret) {
-                               j++;
+                       if (ret)
                                continue;
-                       }
-
-                       seg[i].buf = map[j++].dev_bus_addr |
-                               (req->u.rw.seg[i].first_sect << 9);
                }
+               seg[i].buf = (req->u.rw.seg[i].first_sect << 9);
        }
        return ret;
 }

diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index da78346487ae85019087f7ec6c3df7905f6e22fb..60103e2517ba28ac5c946f32e1bd9e0e6eb7f668 100644 (file)
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -187,7 +187,6 @@ struct persistent_gnt {
        struct page *page;
        grant_ref_t gnt;
        grant_handle_t handle;
-       uint64_t dev_bus_addr;
        struct rb_node node;
 };