The patch titled
Subject: resource: re-factor page_is_ram()
has been added to the -mm mm-nonmm-unstable branch. Its filename is
resource-re-factor-page_is_ram.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/resource-re-factor-page_is_ram.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
Subject: resource: re-factor page_is_ram()
Date: Wed, 1 Jun 2022 22:02:43 +0530
Presently page_is_ram() relies on walk_system_ram_range() that performs a
walk on kernel iomem resources hierarchy with a dummy callback __is_ram().
Before calling find_next_iomem_res(), walk_system_ram_range() does some
book-keeping which can be avoided for page_is_ram() use-case.
Hence this patch proposes to update page_is_ram() to directly call
find_next_iomem_res() with minimal book-keeping needed.
To avoid allocating a 'struct resource' the patch also updates
find_next_iomem_res() to not return -EINVAL in case 'res == NULL'.
Instead our 'struct resource *res' is only populated when its not NULL.
Link: https://lkml.kernel.org/r/20220601163243.3806231-1-vaibhav@xxxxxxxxxxxxx
Signed-off-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
Cc: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/resource.c | 19 ++++++++-----------
1 file changed, 8 insertions(+), 11 deletions(-)
--- a/kernel/resource.c~resource-re-factor-page_is_ram
+++ a/kernel/resource.c
@@ -311,7 +311,7 @@ EXPORT_SYMBOL(release_resource);
*
* If a resource is found, returns 0 and @*res is overwritten with the part
* of the resource that's within [@start..@end]; if none is found, returns
- * -ENODEV. Returns -EINVAL for invalid parameters.
+ * -ENODEV.
*
* @start: start address of the resource searched for
* @end: end address of same resource
@@ -328,9 +328,6 @@ static int find_next_iomem_res(resource_
{
struct resource *p;
- if (!res)
- return -EINVAL;
-
if (start >= end)
return -EINVAL;
@@ -356,7 +353,7 @@ static int find_next_iomem_res(resource_
break;
}
- if (p) {
+ if (p && res) {
/* copy data */
*res = (struct resource) {
.start = max(start, p->start),
@@ -474,18 +471,18 @@ int walk_system_ram_range(unsigned long
return ret;
}
-static int __is_ram(unsigned long pfn, unsigned long nr_pages, void *arg)
-{
- return 1;
-}
-
/*
* This generic page_is_ram() returns true if specified address is
* registered as System RAM in iomem_resource list.
*/
int __weak page_is_ram(unsigned long pfn)
{
- return walk_system_ram_range(pfn, 1, NULL, __is_ram) == 1;
+ const resource_size_t pfn_res = PFN_PHYS(pfn);
+
+ return find_next_iomem_res(pfn_res,
+ pfn_res + 1,
+ IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
+ IORES_DESC_NONE, NULL) == 0;
}
EXPORT_SYMBOL_GPL(page_is_ram);
_
Patches currently in -mm which might be from vaibhav@xxxxxxxxxxxxx are
resource-re-factor-page_is_ram.patch
