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Re: [PATCH 1/2] xen/xenbus: avoid large structs and arrays on the stack



On 11.05.20 20:01, Boris Ostrovsky wrote:
On 5/11/20 3:31 AM, Juergen Gross wrote:
static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,


I wonder whether we can drop valloc/vfree from xenbus_ring_ops' names.

I can do that.



+                                     struct map_ring_valloc *info,
                                      grant_ref_t *gnt_ref,
                                      unsigned int nr_grefs,
                                      void **vaddr)
  {
-       struct xenbus_map_node *node;
+       struct xenbus_map_node *node = info->node;
        int err;
        void *addr;
        bool leaked = false;
-       struct map_ring_valloc_hvm info = {
-               .idx = 0,
-       };
        unsigned int nr_pages = XENBUS_PAGES(nr_grefs);
- if (nr_grefs > XENBUS_MAX_RING_GRANTS)
-               return -EINVAL;
-
-       *vaddr = NULL;
-
-       node = kzalloc(sizeof(*node), GFP_KERNEL);
-       if (!node)
-               return -ENOMEM;
-
        err = alloc_xenballooned_pages(nr_pages, node->hvm.pages);
        if (err)
                goto out_err;
gnttab_foreach_grant(node->hvm.pages, nr_grefs,
                             xenbus_map_ring_setup_grant_hvm,
-                            &info);
+                            info);
err = __xenbus_map_ring(dev, gnt_ref, nr_grefs, node->handles,
-                               info.phys_addrs, GNTMAP_host_map, &leaked);
+                               info, GNTMAP_host_map, &leaked);
        node->nr_handles = nr_grefs;
if (err)
@@ -641,11 +654,13 @@ static int xenbus_map_ring_valloc_hvm(struct 
xenbus_device *dev,
        spin_unlock(&xenbus_valloc_lock);
*vaddr = addr;
+       info->node = NULL;


Is this so that xenbus_map_ring_valloc() doesn't free it accidentally?

Yes.


Juergen




 


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