Fix error path in blkback driver where a grant mapping in the

middle of a batch fails. Spotted by Harry Butterworth (IBM).

Signed-off-by: Keir Fraser <keir@xensource.com>

diff --git a/linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c b/linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c
index 3dc929f0a7ba1c694613f09d4996349fc82dcbc0..d15c062695c3ae4a6545159e805db4eb1995c42c 100644 (file)
--- a/linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c
+++ b/linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c
@@ -340,7 +340,7 @@ static void dispatch_rw_block_io(blkif_t *blkif, blkif_request_t *req)
        struct bio *bio = NULL, *biolist[BLKIF_MAX_SEGMENTS_PER_REQUEST];
        int nbio = 0;
        request_queue_t *q;
-       int ret;
+       int ret, errors = 0;
 
        /* Check that number of segments is sane. */
        nseg = req->nr_segments;
@@ -374,23 +374,23 @@ static void dispatch_rw_block_io(blkif_t *blkif, blkif_request_t *req)
        BUG_ON(ret);
 
        for (i = 0; i < nseg; i++) {
-               if (unlikely(map[i].handle < 0)) {
-                       DPRINTK("invalid buffer -- could not remap it\n");
-                       fast_flush_area(pending_idx, nseg);
-                       goto bad_descriptor;
+               if (likely(map[i].handle >= 0)) {
+                       pending_handle(pending_idx, i) = map[i].handle;
+                       phys_to_machine_mapping[__pa(MMAP_VADDR(
+                               pending_idx, i)) >> PAGE_SHIFT] =
+                               FOREIGN_FRAME(map[i].dev_bus_addr>>PAGE_SHIFT);
+                       fas        = req->frame_and_sects[i];
+                       seg[i].buf = map[i].dev_bus_addr | 
+                               (blkif_first_sect(fas) << 9);
+               } else {
+                       errors++;
                }
-
-               phys_to_machine_mapping[__pa(MMAP_VADDR(
-                       pending_idx, i)) >> PAGE_SHIFT] =
-                       FOREIGN_FRAME(map[i].dev_bus_addr >> PAGE_SHIFT);
-
-               pending_handle(pending_idx, i) = map[i].handle;
        }
 
-       for (i = 0; i < nseg; i++) {
-               fas         = req->frame_and_sects[i];
-               seg[i].buf  = map[i].dev_bus_addr | 
-                       (blkif_first_sect(fas) << 9);
+       if (errors) {
+               DPRINTK("invalid buffer -- could not remap it\n");
+               fast_flush_area(pending_idx, nseg);
+               goto bad_descriptor;
        }
 
        if (vbd_translate(&preq, blkif, operation) != 0) {