Allocate space from the top of a region first, then work downward,
if an architecture desires this.
I think it's too dangerous to do this across the board, because
iomem_resource.end is initialized to -1, which is 0xffffffff_ffffffff
on 64-bit architectures, and most machines can't address the entire
64-bit physical address space. So this patch is only effective if the
architecture defines ARCH_HAS_TOP_DOWN_ALLOC.
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 0xc0000000-0xdfffffff] PCI Bus 0000:02
we attempted to allocate from the [mem 0xbff00000-0xbfffffff] gap first,
then the [mem 0xe0000000-0xf7ffffff] gap.
With this patch, if the architecture defines ARCH_HAS_TOP_DOWN_ALLOC,
we allocate from [mem 0xe0000000-0xf7ffffff] first.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@xxxxxx>
---
kernel/resource.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 70 insertions(+), 0 deletions(-)
diff --git a/kernel/resource.c b/kernel/resource.c
index ace2269..9218e8e 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -357,8 +357,77 @@ int __weak page_is_ram(unsigned long pfn)
return walk_system_ram_range(pfn, 1, NULL, __is_ram) == 1;
}
+#ifdef ARCH_HAS_TOP_DOWN_ALLOC
+/*
+ * 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(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 = *new;
+ resource_size_t start;
+
+ tmp.start = root->end;
+ tmp.end = root->end;
+
+ this = find_sibling_prev(root, NULL);
+ for (;;) {
+ if (this && this->end < root->end)
+ tmp.start = this->end + 1;
+ else
+ tmp.start = root->start;
+ if (tmp.start < min)
+ tmp.start = min;
+ if (tmp.end > max)
+ tmp.end = max;
+ tmp.start = ALIGN(tmp.start, align);
+ if (alignf) {
+ start = alignf(alignf_data, &tmp, size, align);
+ if (tmp.start <= start && start <= tmp.end)
+ tmp.start = start;
+ else
+ tmp.start = tmp.end;
+ }
+ if (tmp.start < tmp.end && tmp.end - tmp.start >= size - 1) {
+ new->start = tmp.start;
+ new->end = tmp.start + size - 1;
+ return 0;
+ }
+ if (!this || this->start == root->start)
+ break;
+ tmp.end = this->start - 1;
+ this = find_sibling_prev(root, this);
+ }
+ return -EBUSY;
+}
+
+#else
+
+/*
+ * 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,
@@ -411,6 +480,7 @@ static int find_resource(struct resource *root, struct resource *new,
}
return -EBUSY;
}
+#endif
/**
* allocate_resource - allocate empty slot in the resource tree given range & alignment
--
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