[PATCH] xen-blkback: use balloon pages for persistent grants

[Roger Pau Monne <roger.pau@citrix.com>]

With current persistent grants implementation we are not freeing the
persistent grants after we disconnect the device. Since grant map
operations change the mfn of the allocated page, and we can no longer
pass it to __free_page without setting the mfn to a sane value, use
balloon grant pages instead, as the gntdev device does.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: xen-devel@lists.xen.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 drivers/block/xen-blkback/blkback.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index c46824f..e6c2f6a 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -46,6 +46,7 @@
 #include <xen/xen.h>
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
+#include <xen/balloon.h>
 #include "common.h"
 
 /*
@@ -239,6 +240,7 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
 			ret = gnttab_unmap_refs(unmap, NULL, pages,
 				segs_to_unmap);
 			BUG_ON(ret);
+			free_xenballooned_pages(segs_to_unmap, pages);
 			segs_to_unmap = 0;
 		}
 
@@ -527,8 +529,8 @@ static int xen_blkbk_map(struct blkif_request *req,
 				GFP_KERNEL);
 			if (!persistent_gnt)
 				return -ENOMEM;
-			persistent_gnt->page = alloc_page(GFP_KERNEL);
-			if (!persistent_gnt->page) {
+			if (alloc_xenballooned_pages(1, &persistent_gnt->page,
+			    false)) {
 				kfree(persistent_gnt);
 				return -ENOMEM;
 			}
-- 
1.7.7.5 (Apple Git-26)