Once we have obtained a resource of a certain type from
find_next_iomem_res(), it doesn't necessarily mean that the whole
resource is usable, and we have cases where a child resource
denotes an exclusion in the initial resource.
Provide a new walker that deals with this exact case, and calls
a callback on each resource fragment that doesn't have a child.
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
include/linux/ioport.h | 4 +++
kernel/resource.c | 80 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 84 insertions(+)
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 8359c50f9988..526314a42ad2 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -323,6 +323,10 @@ extern int
walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start, u64 end,
void *arg, int (*func)(struct resource *, void *));
+extern int
+walk_excluding_child_res(struct resource *res, void *arg,
+ int (*func)(struct resource *, void *));
+
struct resource *devm_request_free_mem_region(struct device *dev,
struct resource *base, unsigned long size);
struct resource *request_free_mem_region(struct resource *base,
diff --git a/kernel/resource.c b/kernel/resource.c
index 311b8d2c9957..1d9b5f653938 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -318,6 +318,86 @@ int release_resource(struct resource *old)
EXPORT_SYMBOL(release_resource);
+/**
+ * walk_excluding_child_res - call a callback function on each fragment of
+ * a resource that do not have a child resource
+ *
+ * @res: the root resource containing the initial range
+ * @arg: function argument for the callback @func
+ * @func: callback function that is called for each qualifying resource area
+ *
+ * For a given resource, remove all the child resources and feed the
+ * resulting fragments to kexec_locate_mem_hole_callback().
+ */
+int walk_excluding_child_res(struct resource *res, void *arg,
+ int (*func)(struct resource *, void *))
+{
+ struct resource *tmp, cursor;
+ int ret = 0;
+
+ cursor = *res;
+
+ /* Use .child for the head of the list, .sibling for the tail */
+ cursor.child = cursor.sibling = NULL;
+
+ read_lock(&resource_lock);
+
+ for (tmp = res->child; tmp; tmp = tmp->sibling) {
+ struct resource *new;
+
+ if (cursor.start < tmp->start) {
+ new = kmalloc(sizeof(*new), GFP_KERNEL);
+ if (!new)
+ goto cleanup;
+
+ *new = (struct resource) {
+ .start = cursor.start,
+ .end = tmp->start - 1,
+ .flags = res->flags,
+ .desc = res->desc,
+ .parent = res->parent,
+ };
+
+ if (!cursor.child)
+ cursor.child = new;
+ if (cursor.sibling)
+ cursor.sibling->sibling = new;
+ cursor.sibling = new;
+ }
+
+ /*
+ * This may result in a resource with a negative size
+ * at the very end of the loop.
+ */
+ cursor.start = tmp->end + 1;
+ }
+
+ read_unlock(&resource_lock);
+
+ /*
+ * At this stage, the list pointed to by cursor.child contains
+ * every non-reserved blocks, completed by 'cursor' which
+ * contains the potential last block (may be empty).
+ */
+ for (tmp = cursor.child; tmp; tmp = tmp->sibling) {
+ ret = func(tmp, arg);
+ if (ret)
+ break;
+ }
+
+ if (!ret && cursor.start <= cursor.end)
+ ret = func(&cursor, tmp);
+
+cleanup:
+ while (cursor.child) {
+ tmp = cursor.child;
+ cursor.child = cursor.child->sibling;
+ kfree(tmp);
+ }
+
+ return ret;
+}
+
/**
* find_next_iomem_res - Finds the lowest iomem resource that covers part of
* [@start..@end].
--
2.30.2
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