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>

diff --git a/kernel/resource.c b/kernel/resource.c
index fb11a58..dc15686 100644 (file)
--- 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;