IO resources: add reserve_region_with_split()

add reserve_region_with_split() to not lose e820 reserved entries if
they overlap with existing IO regions:

with test case by extend 0xe0000000 - 0xeffffff to 0xdd800000 -
we get:
	e0000000-efffffff : PCI MMCONFIG 0
		 e0000000-efffffff : reserved

and in /proc/iomem we get:
	found conflict for reserved [dd800000, efffffff], try to reserve with split
	    __reserve_region_with_split: (PCI Bus #80) [dd000000, ddffffff], res: (reserved) [dd800000, efffffff]
	    __reserve_region_with_split: (PCI Bus #00) [de000000, dfffffff], res: (reserved) [de000000, efffffff]
	initcall pci_subsys_init+0x0/0x121 returned 0 after 381 msecs
in dmesg

various fixes and improvements suggested by Linus.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 71 insertions, 0 deletions

diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 8d3b7a9afd17..fded376b94e3 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -108,6 +108,9 @@ extern struct resource iomem_resource;
 
 extern int request_resource(struct resource *root, struct resource *new);
 extern int release_resource(struct resource *new);
+extern void reserve_region_with_split(struct resource *root,
+                             resource_size_t start, resource_size_t end,
+                             const char *name);
 extern int insert_resource(struct resource *parent, struct resource *new);
 extern void insert_resource_expand_to_fit(struct resource *root, struct resource *new);
 extern int allocate_resource(struct resource *root, struct resource *new,
diff --git a/kernel/resource.c b/kernel/resource.c
index 03d796c1b2e9..414d6fc9131e 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -516,6 +516,74 @@ int adjust_resource(struct resource *res, resource_size_t start, resource_size_t
         return result;
 }
 
+static void __init __reserve_region_with_split(struct resource *root,
+                resource_size_t start, resource_size_t end,
+                const char *name)
+{
+        struct resource *parent = root;
+        struct resource *conflict;
+        struct resource *res = kzalloc(sizeof(*res), GFP_KERNEL);
+
+        if (!res)
+                return;
+
+        res->name = name;
+        res->start = start;
+        res->end = end;
+        res->flags = IORESOURCE_BUSY;
+
+        for (;;) {
+                conflict = __request_resource(parent, res);
+                if (!conflict)
+                        break;
+                if (conflict != parent) {
+                        parent = conflict;
+                        if (!(conflict->flags & IORESOURCE_BUSY))
+                                continue;
+                }
+
+                /* Uhhuh, that didn't work out.. */
+                kfree(res);
+                res = NULL;
+                break;
+        }
+
+        if (!res) {
+                printk(KERN_DEBUG "    __reserve_region_with_split: (%s) [%llx, %llx], res: (%s) [%llx, %llx]\n",
+                         conflict->name, conflict->start, conflict->end,
+                         name, start, end);
+
+                /* failed, split and try again */
+
+                /* conflict coverred whole area */
+                if (conflict->start <= start && conflict->end >= end)
+                        return;
+
+                if (conflict->start > start)
+                        __reserve_region_with_split(root, start, conflict->start-1, name);
+                if (!(conflict->flags & IORESOURCE_BUSY)) {
+                        resource_size_t common_start, common_end;
+
+                        common_start = max(conflict->start, start);
+                        common_end = min(conflict->end, end);
+                        if (common_start < common_end)
+                                __reserve_region_with_split(root, common_start, common_end, name);
+                }
+                if (conflict->end < end)
+                        __reserve_region_with_split(root, conflict->end+1, end, name);
+        }
+
+}
+
+void reserve_region_with_split(struct resource *root,
+                resource_size_t start, resource_size_t end,
+                const char *name)
+{
+        write_lock(&resource_lock);
+        __reserve_region_with_split(root, start, end, name);
+        write_unlock(&resource_lock);
+}
+
 EXPORT_SYMBOL(adjust_resource);
 
 /**