resources: when allocate_resource() fails, leave resource untouched

When "allocate_resource(root, new, size, ...)" fails, we currently
clobber "new".  This is inconvenient for the caller, who might care
about the original contents of the resource.

For example, when pci_bus_alloc_resource() fails, the "can't allocate
mem resource %pR" message from pci_assign_resources() currently contains
junk for the resource start/end.

This patch delays the "new" update until we're about to return success.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 14 insertions, 12 deletions

diff --git a/kernel/resource.c b/kernel/resource.c
index fb11a58b9594..dc15686b7a77 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -308,35 +308,37 @@ static int find_resource(struct resource *root, struct resource *new,
                          void *alignf_data)
 {
         struct resource *this = root->child;
+        resource_size_t start, end;
 
-        new->start = root->start;
+        start = root->start;
         /*
          * Skip past an allocated resource that starts at 0, since the assignment
          * of this->start - 1 to new->end below would cause an underflow.
          */
         if (this && this->start == 0) {
-                new->start = this->end + 1;
+                start = this->end + 1;
                 this = this->sibling;
         }
         for(;;) {
                 if (this)
-                        new->end = this->start - 1;
+                        end = this->start - 1;
                 else
-                        new->end = root->end;
-                if (new->start < min)
-                        new->start = min;
-                if (new->end > max)
-                        new->end = max;
-                new->start = ALIGN(new->start, align);
+                        end = root->end;
+                if (start < min)
+                        start = min;
+                if (end > max)
+                        end = max;
+                start = ALIGN(start, align);
                 if (alignf)
                         alignf(alignf_data, new, size, align);
-                if (new->start < new->end && new->end - new->start >= size - 1) {
-                        new->end = new->start + size - 1;
+                if (start < end && end - start >= size - 1) {
+                        new->start = start;
+                        new->end = start + size - 1;
                         return 0;
                 }
                 if (!this)
                         break;
-                new->start = this->end + 1;
+                start = this->end + 1;
                 this = this->sibling;
         }
         return -EBUSY;