Commit 62a9f5a8 authored by Ankur Arora's avatar Ankur Arora Committed by Andrew Morton
Browse files

mm: introduce clear_pages() and clear_user_pages() 

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: default avatarAnkur Arora <ankur.a.arora@oracle.com>
Acked-by: default avatarDavid 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 8e38607a

include/linux/highmem.h

+33 −0
Original line number Diff line number Diff line
@@ -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)

{

include/linux/mm.h

+20 −0
Original line number Diff line number Diff line
@@ -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);