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@xxxxxx>
---
Documentation/kernel-parameters.txt | 5 ++
include/linux/ioport.h | 1
kernel/resource.c | 89 +++++++++++++++++++++++++++++++++++
3 files changed, 94 insertions(+), 1 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 8dd7248..fe50cbd 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2156,6 +2156,11 @@ and is between 256 and 4096 characters. It is defined in the file
reset_devices [KNL] Force drivers to reset the underlying device
during initialization.
+ resource_alloc_from_bottom
+ Allocate new resources from the beginning of available
+ space, not the end. If you need to use this, please
+ report a bug.
+
resume= [SWSUSP]
Specify the partition device for software suspend
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index b227902..d377ea8 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -112,6 +112,7 @@ struct resource_list {
/* PC/ISA/whatever - the normal PC address spaces: IO and memory */
extern struct resource ioport_resource;
extern struct resource iomem_resource;
+extern int resource_alloc_from_bottom;
extern struct resource *request_resource_conflict(struct resource *root, struct resource *new);
extern int request_resource(struct resource *root, struct resource *new);
diff --git a/kernel/resource.c b/kernel/resource.c
index ace2269..8d337a9 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;
@@ -358,7 +375,74 @@ int __weak page_is_ram(unsigned long pfn)
}
/*
+ * 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 = *new;
+ resource_size_t start;
+
+ 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;
+ 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;
+}
+
+/*
* 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,
@@ -435,7 +519,10 @@ int allocate_resource(struct resource *root, struct resource *new,
int err;
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);
--
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