The patch titled
Subject: bootmem: stop using page->index
has been added to the -mm mm-unstable branch. Its filename is
bootmem-stop-using-page-index.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/bootmem-stop-using-page-index.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: bootmem: stop using page->index
Date: Tue, 23 Jul 2024 16:34:56 +0100
Patch series "page->index removals in mm".
As part of shrinking struct page, we need to stop using page->index. This
patchset gets rid of most of the remaining references to page->index in
mm, as well as increasing the number of functions which take a const
folio/page pointer. It shrinks the text segment of mm by a few hundred
bytes in my test config, probably mostly from removing calls to
compound_head() in page_to_pgoff().
This patch (of 6):
Encode the type into the bottom four bits of page->private and the info
into the remaining bits. Also turn the bootmem type into a named enum.
Link: https://lkml.kernel.org/r/20240723153503.1669586-1-willy@xxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20240723153503.1669586-2-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/mm/init_64.c | 9 ++++-----
include/linux/bootmem_info.h | 25 +++++++++++++++++--------
mm/bootmem_info.c | 11 ++++++-----
mm/sparse.c | 8 ++++----
4 files changed, 31 insertions(+), 22 deletions(-)
--- a/arch/x86/mm/init_64.c~bootmem-stop-using-page-index
+++ a/arch/x86/mm/init_64.c
@@ -983,13 +983,12 @@ int arch_add_memory(int nid, u64 start,
static void __meminit free_pagetable(struct page *page, int order)
{
- unsigned long magic;
- unsigned int nr_pages = 1 << order;
-
/* bootmem page has reserved flag */
if (PageReserved(page)) {
- magic = page->index;
- if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
+ enum bootmem_type type = bootmem_type(page);
+ unsigned long nr_pages = 1 << order;
+
+ if (type == SECTION_INFO || type == MIX_SECTION_INFO) {
while (nr_pages--)
put_page_bootmem(page++);
} else
--- a/include/linux/bootmem_info.h~bootmem-stop-using-page-index
+++ a/include/linux/bootmem_info.h
@@ -6,11 +6,10 @@
#include <linux/kmemleak.h>
/*
- * Types for free bootmem stored in page->lru.next. These have to be in
- * some random range in unsigned long space for debugging purposes.
+ * Types for free bootmem stored in the low bits of page->private.
*/
-enum {
- MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE = 12,
+enum bootmem_type {
+ MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE = 1,
SECTION_INFO = MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE,
MIX_SECTION_INFO,
NODE_INFO,
@@ -21,9 +20,19 @@ enum {
void __init register_page_bootmem_info_node(struct pglist_data *pgdat);
void get_page_bootmem(unsigned long info, struct page *page,
- unsigned long type);
+ enum bootmem_type type);
void put_page_bootmem(struct page *page);
+static inline enum bootmem_type bootmem_type(const struct page *page)
+{
+ return (unsigned long)page->private & 0xf;
+}
+
+static inline unsigned long bootmem_info(const struct page *page)
+{
+ return (unsigned long)page->private >> 4;
+}
+
/*
* Any memory allocated via the memblock allocator and not via the
* buddy will be marked reserved already in the memmap. For those
@@ -31,7 +40,7 @@ void put_page_bootmem(struct page *page)
*/
static inline void free_bootmem_page(struct page *page)
{
- unsigned long magic = page->index;
+ enum bootmem_type type = bootmem_type(page);
/*
* The reserve_bootmem_region sets the reserved flag on bootmem
@@ -39,7 +48,7 @@ static inline void free_bootmem_page(str
*/
VM_BUG_ON_PAGE(page_ref_count(page) != 2, page);
- if (magic == SECTION_INFO || magic == MIX_SECTION_INFO)
+ if (type == SECTION_INFO || type == MIX_SECTION_INFO)
put_page_bootmem(page);
else
VM_BUG_ON_PAGE(1, page);
@@ -54,7 +63,7 @@ static inline void put_page_bootmem(stru
}
static inline void get_page_bootmem(unsigned long info, struct page *page,
- unsigned long type)
+ enum bootmem_type type)
{
}
--- a/mm/bootmem_info.c~bootmem-stop-using-page-index
+++ a/mm/bootmem_info.c
@@ -14,23 +14,24 @@
#include <linux/memory_hotplug.h>
#include <linux/kmemleak.h>
-void get_page_bootmem(unsigned long info, struct page *page, unsigned long type)
+void get_page_bootmem(unsigned long info, struct page *page,
+ enum bootmem_type type)
{
- page->index = type;
+ BUG_ON(type > 0xf);
+ BUG_ON(info > (ULONG_MAX >> 4));
SetPagePrivate(page);
- set_page_private(page, info);
+ set_page_private(page, info << 4 | type);
page_ref_inc(page);
}
void put_page_bootmem(struct page *page)
{
- unsigned long type = page->index;
+ enum bootmem_type type = bootmem_type(page);
BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE);
if (page_ref_dec_return(page) == 1) {
- page->index = 0;
ClearPagePrivate(page);
set_page_private(page, 0);
INIT_LIST_HEAD(&page->lru);
--- a/mm/sparse.c~bootmem-stop-using-page-index
+++ a/mm/sparse.c
@@ -721,19 +721,19 @@ static void depopulate_section_memmap(un
static void free_map_bootmem(struct page *memmap)
{
unsigned long maps_section_nr, removing_section_nr, i;
- unsigned long magic, nr_pages;
+ unsigned long type, nr_pages;
struct page *page = virt_to_page(memmap);
nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
>> PAGE_SHIFT;
for (i = 0; i < nr_pages; i++, page++) {
- magic = page->index;
+ type = bootmem_type(page);
- BUG_ON(magic == NODE_INFO);
+ BUG_ON(type == NODE_INFO);
maps_section_nr = pfn_to_section_nr(page_to_pfn(page));
- removing_section_nr = page_private(page);
+ removing_section_nr = bootmem_info(page);
/*
* When this function is called, the removing section is
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
bootmem-stop-using-page-index.patch
mm-constify-page_address_in_vma.patch
mm-convert-page_to_pgoff-to-page_pgoff.patch
mm-mass-constification-of-folio-page-pointers.patch
mm-remove-references-to-page-index-in-huge_memoryc.patch
mm-use-page-private-instead-of-page-index-in-percpu.patch
