[65/91] kernel/resource: refactor __request_region to allow external locking

Commit Message

Andrew Morton May 7, 2021, 1:05 a.m. UTC

From: Alistair Popple <[e-mail]>
Subject: kernel/resource: refactor __request_region to allow external locking

Refactor the portion of __request_region() done whilst holding the
resource_lock into a separate function to allow callers to hold the lock.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Alistair Popple <[e-mail]>
Reviewed-by: David Hildenbrand <[e-mail]>
Cc: Balbir Singh <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Jerome Glisse <[e-mail]>
Cc: John Hubbard <[e-mail]>
Cc: Muchun Song <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 kernel/resource.c |   52 +++++++++++++++++++++++++++-----------------
 1 file changed, 32 insertions(+), 20 deletions(-)

Patch

--- a/kernel/resource.c~kernel-resource-refactor-__request_region-to-allow-external-locking
+++ a/kernel/resource.c
@@ -1160,31 +1160,16 @@  struct address_space *iomem_get_mapping(
 	return smp_load_acquire(&iomem_inode)->i_mapping;
 }
 
-/**
- * __request_region - create a new busy resource region
- * @parent: parent resource descriptor
- * @start: resource start address
- * @n: resource region size
- * @name: reserving caller's ID string
- * @flags: IO resource flags
- */
-struct resource * __request_region(struct resource *parent,
+static int __request_region_locked(struct resource *res, struct resource *parent,
 				   resource_size_t start, resource_size_t n,
 				   const char *name, int flags)
 {
 	DECLARE_WAITQUEUE(wait, current);
-	struct resource *res = alloc_resource(GFP_KERNEL);
-	struct resource *orig_parent = parent;
-
-	if (!res)
-		return NULL;
 
 	res->name = name;
 	res->start = start;
 	res->end = start + n - 1;
 
-	write_lock(&resource_lock);
-
 	for (;;) {
 		struct resource *conflict;
 
@@ -1220,13 +1205,40 @@  struct resource * __request_region(struc
 			continue;
 		}
 		/* Uhhuh, that didn't work out.. */
-		free_resource(res);
-		res = NULL;
-		break;
+		return -EBUSY;
 	}
+
+	return 0;
+}
+
+/**
+ * __request_region - create a new busy resource region
+ * @parent: parent resource descriptor
+ * @start: resource start address
+ * @n: resource region size
+ * @name: reserving caller's ID string
+ * @flags: IO resource flags
+ */
+struct resource *__request_region(struct resource *parent,
+				  resource_size_t start, resource_size_t n,
+				  const char *name, int flags)
+{
+	struct resource *res = alloc_resource(GFP_KERNEL);
+	int ret;
+
+	if (!res)
+		return NULL;
+
+	write_lock(&resource_lock);
+	ret = __request_region_locked(res, parent, start, n, name, flags);
 	write_unlock(&resource_lock);
 
-	if (res && orig_parent == &iomem_resource)
+	if (ret) {
+		free_resource(res);
+		return NULL;
+	}
+
+	if (parent == &iomem_resource)
 		revoke_iomem(res);
 
 	return res;