Merge branch 'stable/for-jens-3.8' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen into for-linus

Konrad writes:

Please git pull the following branch:

 git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git stable/for-jens-3.8

which has a bug-fix to the xen-blkfront and xen-blkback driver
when using the persistent mode. An issue was discovered where LVM
disks could not be read correctly and this fixes it. There
is also a change in llist.h which has been blessed by akpm.

1 files changed, 11 insertions, 7 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 74374fb762aa..5ac841ff6cc7 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -161,10 +161,12 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 static void make_response(struct xen_blkif *blkif, u64 id,
 			  unsigned short op, int st);
 
-#define foreach_grant(pos, rbtree, node) \
-	for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node); \
+#define foreach_grant_safe(pos, n, rbtree, node) \
+	for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
+	     (n) = rb_next(&(pos)->node); \
 	     &(pos)->node != NULL; \
-	     (pos) = container_of(rb_next(&(pos)->node), typeof(*(pos)), node))
+	     (pos) = container_of(n, typeof(*(pos)), node), \
+	     (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)
 
 
 static void add_persistent_gnt(struct rb_root *root,
@@ -217,10 +219,11 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
 	struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 	struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 	struct persistent_gnt *persistent_gnt;
+	struct rb_node *n;
 	int ret = 0;
 	int segs_to_unmap = 0;
 
-	foreach_grant(persistent_gnt, root, node) {
+	foreach_grant_safe(persistent_gnt, n, root, node) {
 		BUG_ON(persistent_gnt->handle ==
 			BLKBACK_INVALID_HANDLE);
 		gnttab_set_unmap_op(&unmap[segs_to_unmap],
@@ -230,9 +233,6 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
 			persistent_gnt->handle);
 
 		pages[segs_to_unmap] = persistent_gnt->page;
-		rb_erase(&persistent_gnt->node, root);
-		kfree(persistent_gnt);
-		num--;
 
 		if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
 			!rb_next(&persistent_gnt->node)) {
@@ -241,6 +241,10 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
 			BUG_ON(ret);
 			segs_to_unmap = 0;
 		}
+
+		rb_erase(&persistent_gnt->node, root);
+		kfree(persistent_gnt);
+		num--;
 	}
 	BUG_ON(num != 0);
 }