Commit 0060ef3b authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Linus Torvalds
Browse files

mm: support THPs in zero_user_segments 

We can only kmap() one subpage of a THP at a time, so loop over all
relevant subpages, skipping ones which don't need to be zeroed.  This is
too large to inline when THPs are enabled and we actually need highmem, so
put it in highmem.c.

[willy@infradead.org: start1 was allowed to be less than start2]

Link: https://lkml.kernel.org/r/20201124041507.28996-1-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5e5dda81

include/linux/highmem.h

+15 −4
Original line number Diff line number Diff line
@@ -284,13 +284,22 @@ static inline void clear_highpage(struct page *page) 
	kunmap_atomic(kaddr);

}



/*

 * If we pass in a base or tail page, we can zero up to PAGE_SIZE.

 * If we pass in a head page, we can zero up to the size of the compound page.

 */

#if defined(CONFIG_HIGHMEM) && defined(CONFIG_TRANSPARENT_HUGEPAGE)

void zero_user_segments(struct page *page, unsigned start1, unsigned end1,

		unsigned start2, unsigned end2);

#else /* !HIGHMEM || !TRANSPARENT_HUGEPAGE */

static inline void zero_user_segments(struct page *page,

		unsigned start1, unsigned end1,

		unsigned start2, unsigned end2)

{

	void *kaddr = kmap_atomic(page);

	unsigned int i;



	BUG_ON(end1 > PAGE_SIZE || end2 > PAGE_SIZE);

	BUG_ON(end1 > page_size(page) || end2 > page_size(page));



	if (end1 > start1)

		memset(kaddr + start1, 0, end1 - start1);
@@ -299,8 +308,10 @@ static inline void zero_user_segments(struct page *page, 
		memset(kaddr + start2, 0, end2 - start2);



	kunmap_atomic(kaddr);

	flush_dcache_page(page);

	for (i = 0; i < compound_nr(page); i++)

		flush_dcache_page(page + i);

}

#endif /* !HIGHMEM || !TRANSPARENT_HUGEPAGE */



static inline void zero_user_segment(struct page *page,

	unsigned start, unsigned end)

mm/highmem.c

+52 −0
Original line number Diff line number Diff line
@@ -369,6 +369,58 @@ void kunmap_high(struct page *page) 
}



EXPORT_SYMBOL(kunmap_high);



#ifdef CONFIG_TRANSPARENT_HUGEPAGE

void zero_user_segments(struct page *page, unsigned start1, unsigned end1,

		unsigned start2, unsigned end2)

{

	unsigned int i;



	BUG_ON(end1 > page_size(page) || end2 > page_size(page));



	for (i = 0; i < compound_nr(page); i++) {

		void *kaddr = NULL;



		if (start1 < PAGE_SIZE || start2 < PAGE_SIZE)

			kaddr = kmap_atomic(page + i);



		if (start1 >= PAGE_SIZE) {

			start1 -= PAGE_SIZE;

			end1 -= PAGE_SIZE;

		} else {

			unsigned this_end = min_t(unsigned, end1, PAGE_SIZE);



			if (end1 > start1)

				memset(kaddr + start1, 0, this_end - start1);

			end1 -= this_end;

			start1 = 0;

		}



		if (start2 >= PAGE_SIZE) {

			start2 -= PAGE_SIZE;

			end2 -= PAGE_SIZE;

		} else {

			unsigned this_end = min_t(unsigned, end2, PAGE_SIZE);



			if (end2 > start2)

				memset(kaddr + start2, 0, this_end - start2);

			end2 -= this_end;

			start2 = 0;

		}



		if (kaddr) {

			kunmap_atomic(kaddr);

			flush_dcache_page(page + i);

		}



		if (!end1 && !end2)

			break;

	}



	BUG_ON((start1 | start2 | end1 | end2) != 0);

}

EXPORT_SYMBOL(zero_user_segments);

#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

#endif	/* CONFIG_HIGHMEM */



#if defined(HASHED_PAGE_VIRTUAL)

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