From 0060ef3b4e6dd1410da164d48a595eadb2fb02f7 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Mon, 14 Dec 2020 19:12:59 -0800 Subject: [PATCH] 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: Matthew Wilcox (Oracle) Cc: Yang Shi Cc: Jan Kara Cc: Michal Hocko Cc: Zi Yan Cc: Song Liu Cc: Mel Gorman Cc: Naresh Kamboju Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/highmem.h | 19 +++++++++++---- mm/highmem.c | 52 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 67 insertions(+), 4 deletions(-) diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 14e6202ce47f..8e21fe82b3a3 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -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) + 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) diff --git a/mm/highmem.c b/mm/highmem.c index 1352a27951e3..0ee87a9e0cbf 100644 --- a/mm/highmem.c +++ b/mm/highmem.c @@ -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)