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authorBjorn Helgaas <bjorn.helgaas@hp.com>2010-10-26 15:41:33 -0600
committerJesse Barnes <jbarnes@virtuousgeek.org>2010-10-26 15:33:31 -0700
commite7f8567db9a7f6b3151b0b275e245c1cef0d9c70 (patch)
treef04a01581e86ec2b8c175b9f27648679c70d592c /kernel
parenta1862e31079149a52b6223776228c3aee493d4a7 (diff)
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resources: support allocating space within a region from the top down
Allocate space from the top of a region first, then work downward, if an architecture desires this. When we allocate space from a resource, we look for gaps between children of the resource. Previously, we always looked at gaps from the bottom up. For example, given this: [mem 0xbff00000-0xf7ffffff] PCI Bus 0000:00 [mem 0xbff00000-0xbfffffff] gap -- available [mem 0xc0000000-0xdfffffff] PCI Bus 0000:02 [mem 0xe0000000-0xf7ffffff] gap -- available we attempted to allocate from the [mem 0xbff00000-0xbfffffff] gap first, then the [mem 0xe0000000-0xf7ffffff] gap. With this patch an architecture can choose to allocate from the top gap [mem 0xe0000000-0xf7ffffff] first. We can't do this across the board because iomem_resource.end is initialized to 0xffffffff_ffffffff on 64-bit architectures, and most machines can't address the entire 64-bit physical address space. Therefore, we only allocate top-down if the arch requests it by clearing "resource_alloc_from_bottom". Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/resource.c98
1 files changed, 94 insertions, 4 deletions
diff --git a/kernel/resource.c b/kernel/resource.c
index e15b922d4ba..716b6804077 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -40,6 +40,23 @@ EXPORT_SYMBOL(iomem_resource);
static DEFINE_RWLOCK(resource_lock);
+/*
+ * By default, we allocate free space bottom-up. The architecture can request
+ * top-down by clearing this flag. The user can override the architecture's
+ * choice with the "resource_alloc_from_bottom" kernel boot option, but that
+ * should only be a debugging tool.
+ */
+int resource_alloc_from_bottom = 1;
+
+static __init int setup_alloc_from_bottom(char *s)
+{
+ printk(KERN_INFO
+ "resource: allocating from bottom-up; please report a bug\n");
+ resource_alloc_from_bottom = 1;
+ return 0;
+}
+early_param("resource_alloc_from_bottom", setup_alloc_from_bottom);
+
static void *r_next(struct seq_file *m, void *v, loff_t *pos)
{
struct resource *p = v;
@@ -380,7 +397,74 @@ static bool resource_contains(struct resource *res1, struct resource *res2)
}
/*
+ * Find the resource before "child" in the sibling list of "root" children.
+ */
+static struct resource *find_sibling_prev(struct resource *root, struct resource *child)
+{
+ struct resource *this;
+
+ for (this = root->child; this; this = this->sibling)
+ if (this->sibling == child)
+ return this;
+
+ return NULL;
+}
+
+/*
+ * Find empty slot in the resource tree given range and alignment.
+ * This version allocates from the end of the root resource first.
+ */
+static int find_resource_from_top(struct resource *root, struct resource *new,
+ resource_size_t size, resource_size_t min,
+ resource_size_t max, resource_size_t align,
+ resource_size_t (*alignf)(void *,
+ const struct resource *,
+ resource_size_t,
+ resource_size_t),
+ void *alignf_data)
+{
+ struct resource *this;
+ struct resource tmp, avail, alloc;
+
+ tmp.start = root->end;
+ tmp.end = root->end;
+
+ this = find_sibling_prev(root, NULL);
+ for (;;) {
+ if (this) {
+ if (this->end < root->end)
+ tmp.start = this->end + 1;
+ } else
+ tmp.start = root->start;
+
+ resource_clip(&tmp, min, max);
+
+ /* Check for overflow after ALIGN() */
+ avail = *new;
+ avail.start = ALIGN(tmp.start, align);
+ avail.end = tmp.end;
+ if (avail.start >= tmp.start) {
+ alloc.start = alignf(alignf_data, &avail, size, align);
+ alloc.end = alloc.start + size - 1;
+ if (resource_contains(&avail, &alloc)) {
+ new->start = alloc.start;
+ new->end = alloc.end;
+ return 0;
+ }
+ }
+
+ if (!this || this->start == root->start)
+ break;
+
+ tmp.end = this->start - 1;
+ this = find_sibling_prev(root, this);
+ }
+ return -EBUSY;
+}
+
+/*
* Find empty slot in the resource tree given range and alignment.
+ * This version allocates from the beginning of the root resource first.
*/
static int find_resource(struct resource *root, struct resource *new,
resource_size_t size, resource_size_t min,
@@ -396,14 +480,15 @@ static int find_resource(struct resource *root, struct resource *new,
tmp.start = root->start;
/*
- * Skip past an allocated resource that starts at 0, since the assignment
- * of this->start - 1 to tmp->end below would cause an underflow.
+ * Skip past an allocated resource that starts at 0, since the
+ * assignment of this->start - 1 to tmp->end below would cause an
+ * underflow.
*/
if (this && this->start == 0) {
tmp.start = this->end + 1;
this = this->sibling;
}
- for(;;) {
+ for (;;) {
if (this)
tmp.end = this->start - 1;
else
@@ -424,8 +509,10 @@ static int find_resource(struct resource *root, struct resource *new,
return 0;
}
}
+
if (!this)
break;
+
tmp.start = this->end + 1;
this = this->sibling;
}
@@ -458,7 +545,10 @@ int allocate_resource(struct resource *root, struct resource *new,
alignf = simple_align_resource;
write_lock(&resource_lock);
- err = find_resource(root, new, size, min, max, align, alignf, alignf_data);
+ if (resource_alloc_from_bottom)
+ err = find_resource(root, new, size, min, max, align, alignf, alignf_data);
+ else
+ err = find_resource_from_top(root, new, size, min, max, align, alignf, alignf_data);
if (err >= 0 && __request_resource(root, new))
err = -EBUSY;
write_unlock(&resource_lock);