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 de1f319f7bd7e0118a960b5bd23fd286a6ba343e..d40beb39bf909e7456b698732cd5c7b406233b57 100644 (file)
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -621,9 +621,7 @@ 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;
@@ -631,7 +629,8 @@ static int xen_blkbk_map(struct blkif_request *req,
                        if (ret)
                                continue;
 
-                       seg[i].buf = persistent_gnts[i]->dev_bus_addr |
+                       seg[i].buf = pfn_to_mfn(page_to_pfn(
+                               persistent_gnts[i]->page)) << PAGE_SHIFT |
                                (req->u.rw.seg[i].first_sect << 9);
                } else {
                        pending_handle(pending_req, i) = map[j].handle;

diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index 6072390c7f57ef724bee4476502eb78d63941c7c..f338f8a083ad760a2db3bcc6037a870ccad82393 100644 (file)
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -172,7 +172,6 @@ struct persistent_gnt {
        struct page *page;
        grant_ref_t gnt;
        grant_handle_t handle;
-       uint64_t dev_bus_addr;
        struct rb_node node;
 };