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.

3 files changed, 42 insertions, 11 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);
 }
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 96e9b00db081..11043c18ac5a 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -792,6 +792,7 @@ static void blkif_free(struct blkfront_info *info, int suspend)
 {
         struct llist_node *all_gnts;
         struct grant *persistent_gnt;
+        struct llist_node *n;
 
         /* Prevent new requests being issued until we fix things up. */
         spin_lock_irq(&info->io_lock);
@@ -804,7 +805,7 @@ static void blkif_free(struct blkfront_info *info, int suspend)
         /* Remove all persistent grants */
         if (info->persistent_gnts_c) {
                 all_gnts = llist_del_all(&info->persistent_gnts);
-                llist_for_each_entry(persistent_gnt, all_gnts, node) {
+                llist_for_each_entry_safe(persistent_gnt, n, all_gnts, node) {
                         gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
                         __free_page(pfn_to_page(persistent_gnt->pfn));
                         kfree(persistent_gnt);
@@ -835,7 +836,7 @@ static void blkif_free(struct blkfront_info *info, int suspend)
 static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
                              struct blkif_response *bret)
 {
-        int i;
+        int i = 0;
         struct bio_vec *bvec;
         struct req_iterator iter;
         unsigned long flags;
@@ -852,7 +853,8 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
                  */
                 rq_for_each_segment(bvec, s->request, iter) {
                         BUG_ON((bvec->bv_offset + bvec->bv_len) > PAGE_SIZE);
-                        i = offset >> PAGE_SHIFT;
+                        if (bvec->bv_offset < offset)
+                                i++;
                         BUG_ON(i >= s->req.u.rw.nr_segments);
                         shared_data = kmap_atomic(
                                 pfn_to_page(s->grants_used[i]->pfn));
@@ -861,7 +863,7 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
                                 bvec->bv_len);
                         bvec_kunmap_irq(bvec_data, &flags);
                         kunmap_atomic(shared_data);
-                        offset += bvec->bv_len;
+                        offset = bvec->bv_offset + bvec->bv_len;
                 }
         }
         /* Add the persistent grant into the list of free grants */
diff --git a/include/linux/llist.h b/include/linux/llist.h
index a5199f6d0e82..d0ab98f73d38 100644
--- a/include/linux/llist.h
+++ b/include/linux/llist.h
@@ -125,6 +125,31 @@ static inline void init_llist_head(struct llist_head *list)
              (pos) = llist_entry((pos)->member.next, typeof(*(pos)), member))
 
 /**
+ * llist_for_each_entry_safe - iterate safely against remove over some entries
+ * of lock-less list of given type.
+ * @pos:        the type * to use as a loop cursor.
+ * @n:          another type * to use as a temporary storage.
+ * @node:       the fist entry of deleted list entries.
+ * @member:     the name of the llist_node with the struct.
+ *
+ * In general, some entries of the lock-less list can be traversed
+ * safely only after being removed from list, so start with an entry
+ * instead of list head. This variant allows removal of entries
+ * as we iterate.
+ *
+ * If being used on entries deleted from lock-less list directly, the
+ * traverse order is from the newest to the oldest added entry.  If
+ * you want to traverse from the oldest to the newest, you must
+ * reverse the order by yourself before traversing.
+ */
+#define llist_for_each_entry_safe(pos, n, node, member)         \
+        for ((pos) = llist_entry((node), typeof(*(pos)), member),       \
+             (n) = (pos)->member.next;                                  \
+             &(pos)->member != NULL;                                    \
+             (pos) = llist_entry(n, typeof(*(pos)), member),            \
+             (n) = (&(pos)->member != NULL) ? (pos)->member.next : NULL)
+
+/**
  * llist_empty - tests whether a lock-less list is empty
  * @head:       the list to test
  *