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mm: introduce clear_pages() and clear_user_pages()

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Introduce clear_pages(), to be overridden by architectures that support
more efficient clearing of consecutive pages.

Also introduce clear_user_pages(), however, we will not expect this
function to be overridden anytime soon.

As we do for clear_user_page(), define clear_user_pages() only if the
architecture does not define clear_user_highpage().

That is because if the architecture does define clear_user_highpage(),
then it likely needs some flushing magic when clearing user pages or
highpages.  This means we can get away without defining
clear_user_pages(), since, much like its single page sibling, its only
potential user is the generic clear_user_highpages() which should instead
be using clear_user_highpage().

Link: https://lkml.kernel.org/r/20260107072009.1615991-3-ankur.a.arora@oracle.com
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Konrad Rzessutek Wilk <konrad.wilk@oracle.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Li Zhe <lizhe.67@bytedance.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@amd.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Ankur Arora 2026-01-06 23:20:03 -08:00 committed by Andrew Morton
parent 8e38607aa4
commit 62a9f5a85b
2 changed files with 53 additions and 0 deletions
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33
include/linux/highmem.h
View File

@ -218,6 +218,39 @@ static inline void clear_user_page(void *addr, unsigned long vaddr, struct page
}
#endif
/**
* clear_user_pages() - clear a page range to be mapped to user space
* @addr: start address
* @vaddr: start address of the user mapping
* @page: start page
* @npages: number of pages
*
* Assumes that the region (@addr, +@npages) has been validated
* already so this does no exception handling.
*
* If the architecture provides a clear_user_page(), use that;
* otherwise, we can safely use clear_pages().
*/
static inline void clear_user_pages(void *addr, unsigned long vaddr,
struct page *page, unsigned int npages)
{
#ifdef clear_user_page
do {
clear_user_page(addr, vaddr, page);
addr += PAGE_SIZE;
vaddr += PAGE_SIZE;
page++;
} while (--npages);
#else
/*
* Prefer clear_pages() to allow for architectural optimizations
* when operating on contiguous page ranges.
*/
clear_pages(addr, npages);
#endif
}
/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
{

20
include/linux/mm.h
View File

@ -4198,6 +4198,26 @@ static inline void clear_page_guard(struct zone *zone, struct page *page,
unsigned int order) {}
#endif /* CONFIG_DEBUG_PAGEALLOC */
#ifndef clear_pages
/**
* clear_pages() - clear a page range for kernel-internal use.
* @addr: start address
* @npages: number of pages
*
* Use clear_user_pages() instead when clearing a page range to be
* mapped to user space.
*
* Does absolutely no exception handling.
*/
static inline void clear_pages(void *addr, unsigned int npages)
{
do {
clear_page(addr);
addr += PAGE_SIZE;
} while (--npages);
}
#endif
#ifdef __HAVE_ARCH_GATE_AREA
extern struct vm_area_struct *get_gate_vma(struct mm_struct *mm);
extern int in_gate_area_no_mm(unsigned long addr);