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mm: provide free_reserved_pages(), removing x86 variant

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Let's extend free_reserved_page() in page_alloc.c to
free_reserved_pages(), dropping the custom x86 variant.  The common-code
variant will consume an order, so adjust the x86 callers accordingly.

Make free_reserved_pages() assume that we are freeing ordinary high-order
pages, just with the special "reserved" flavor.  The target use case for
now is freeing vmemmap PMD pages.

Set the refcount directly to 0 (instead of 1) and call
__free_frozen_pages().  Set the page count to 0 before clearing
PG_reserved, so someone checking PG_reserved (and not finding it set) to
then try grabbing a ref would not suddenly have that ref be dropped.  That
is arguably cleaner and safer than the old way of doing it.

Add some kerneldoc.  Use a single adjust_managed_page_count() call.

Link: https://lore.kernel.org/20260716-bootmem_info_part2-v2-2-4afc76c73d61@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Brendan Jackman <brendan.jackman@linux.dev>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand (Arm)
2026-07-16 16:51:01 +02:00
committed by Andrew Morton
parent 5e83b4944d
commit d79db3f396
3 changed files with 33 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
arch/x86/mm/init_64.c
View File

@@ -1000,12 +1000,6 @@ int arch_add_memory(int nid, u64 start, u64 size,
return add_pages(nid, start_pfn, nr_pages, params);
}
static void free_reserved_pages(struct page *page, unsigned long nr_pages)
{
while (nr_pages--)
free_reserved_page(page++);
}
static void __meminit free_pagetable(struct page *page)
{
/* bootmem page has reserved flag */
@@ -1038,7 +1032,7 @@ static void __meminit free_vmemmap_pages(struct page *page, unsigned int order,
while (nr_pages--)
put_page_bootmem(page++);
} else {
free_reserved_pages(page, nr_pages);
free_reserved_pages(page, order);
}
} else {
__free_pages(page, order);

8
include/linux/mm.h
View File

@@ -3996,8 +3996,12 @@ extern unsigned long free_reserved_area(void *start, void *end,
extern void adjust_managed_page_count(struct page *page, long count);
/* Free the reserved page into the buddy system, so it gets managed. */
void free_reserved_page(struct page *page);
void free_reserved_pages(struct page *page, unsigned int order);
static inline void free_reserved_page(struct page *page)
{
free_reserved_pages(page, 0);
}
static inline void mark_page_reserved(struct page *page)
{

33
mm/page_alloc.c
View File

@@ -6389,15 +6389,34 @@ void adjust_managed_page_count(struct page *page, long count)
}
EXPORT_SYMBOL(adjust_managed_page_count);
void free_reserved_page(struct page *page)
/**
* free_reserved_pages - free reserved pages
* @page: First page to free.
* @order: The page order to free.
*
* Free pages allocated through memblock during boot, letting the buddy
* manage them from now on.
*
* @page must be naturally aligned to the order and the order must not
* exceed MAX_PAGE_ORDER. All pages must be reserved.
*/
void free_reserved_pages(struct page *page, unsigned int order)
{
clear_page_tag_ref(page);
ClearPageReserved(page);
init_page_count(page);
__free_page(page);
adjust_managed_page_count(page, 1);
const unsigned long nr_pages = 1UL << order;
int i;
VM_WARN_ON_ONCE(!IS_ALIGNED(page_to_pfn(page), nr_pages));
VM_WARN_ON_ONCE(order > MAX_PAGE_ORDER);
for (i = 0; i < nr_pages; i++) {
clear_page_tag_ref(page + i);
set_page_count(page + i, 0);
ClearPageReserved(page + i);
}
adjust_managed_page_count(page, nr_pages);
__free_frozen_pages(page, order, FPI_NONE);
}
EXPORT_SYMBOL(free_reserved_page);
EXPORT_SYMBOL(free_reserved_pages);
static int page_alloc_cpu_dead(unsigned int cpu)
{