xen/blkback: persistent-grants fixes

This patch contains fixes for persistent grants implementation v2:

 * handle == 0 is a valid handle, so initialize grants in blkback
   setting the handle to BLKBACK_INVALID_HANDLE instead of 0. Reported
   by Konrad Rzeszutek Wilk.

 * new_map is a boolean, use "true" or "false" instead of 1 and 0.
   Reported by Konrad Rzeszutek Wilk.

 * blkfront announces the persistent-grants feature as
   feature-persistent-grants, use feature-persistent instead which is
   consistent with blkback and the public Xen headers.

 * Add a consistency check in blkfront to make sure we don't try to
   access segments that have not been set.

Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
[v1: The new_map int->bool had already been changed]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

3 files changed, 9 insertions, 5 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index d7dd5cbdac5f..a05961683efa 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -512,7 +512,7 @@ static int xen_blkbk_map(struct blkif_request *req,
                          * not mapped but we have room for it
                          */
                         new_map = true;
-                        persistent_gnt = kzalloc(
+                        persistent_gnt = kmalloc(
                                 sizeof(struct persistent_gnt),
                                 GFP_KERNEL);
                         if (!persistent_gnt)
@@ -523,6 +523,7 @@ static int xen_blkbk_map(struct blkif_request *req,
                                 return -ENOMEM;
                         }
                         persistent_gnt->gnt = req->u.rw.seg[i].gref;
+                        persistent_gnt->handle = BLKBACK_INVALID_HANDLE;
 
                         pages_to_gnt[segs_to_map] =
                                 persistent_gnt->page;
@@ -584,7 +585,8 @@ static int xen_blkbk_map(struct blkif_request *req,
          */
         bitmap_zero(pending_req->unmap_seg, BLKIF_MAX_SEGMENTS_PER_REQUEST);
         for (i = 0, j = 0; i < nseg; i++) {
-                if (!persistent_gnts[i] || !persistent_gnts[i]->handle) {
+                if (!persistent_gnts[i] ||
+                    persistent_gnts[i]->handle == BLKBACK_INVALID_HANDLE) {
                         /* This is a newly mapped grant */
                         BUG_ON(j >= segs_to_map);
                         if (unlikely(map[j].status != 0)) {
@@ -601,7 +603,8 @@ static int xen_blkbk_map(struct blkif_request *req,
                         }
                 }
                 if (persistent_gnts[i]) {
-                        if (!persistent_gnts[i]->handle) {
+                        if (persistent_gnts[i]->handle ==
+                            BLKBACK_INVALID_HANDLE) {
                                 /*
                                  * If this is a new persistent grant
                                  * save the handler
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index b2250265308a..a03ecbb0044c 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -760,7 +760,7 @@ static int connect_ring(struct backend_info *be)
                 return -1;
         }
         err = xenbus_gather(XBT_NIL, dev->otherend,
-                            "feature-persistent-grants", "%u",
+                            "feature-persistent", "%u",
                             &pers_grants, NULL);
         if (err)
                 pers_grants = 0;
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 911d733d21b6..f1de806b0a63 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -852,6 +852,7 @@ 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;
+                        BUG_ON(i >= s->req.u.rw.nr_segments);
                         shared_data = kmap_atomic(
                                 pfn_to_page(s->grants_used[i]->pfn));
                         bvec_data = bvec_kmap_irq(bvec, &flags);
@@ -1069,7 +1070,7 @@ again:
                 goto abort_transaction;
         }
         err = xenbus_printf(xbt, dev->nodename,
-                            "feature-persistent-grants", "%u", 1);
+                            "feature-persistent", "%u", 1);
         if (err)
                 dev_warn(&dev->dev,
                          "writing persistent grants feature to xenbus");