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Date: Mon, 22 Mar 2021 20:48:57 -0400 From: Peter Xu <peterx@...hat.com> To: linux-kernel@...r.kernel.org, linux-mm@...ck.org Cc: "Kirill A . Shutemov" <kirill@...temov.name>, Jerome Glisse <jglisse@...hat.com>, Mike Kravetz <mike.kravetz@...cle.com>, Matthew Wilcox <willy@...radead.org>, Andrew Morton <akpm@...ux-foundation.org>, Axel Rasmussen <axelrasmussen@...gle.com>, Hugh Dickins <hughd@...gle.com>, peterx@...hat.com, Nadav Amit <nadav.amit@...il.com>, Andrea Arcangeli <aarcange@...hat.com>, Mike Rapoport <rppt@...ux.vnet.ibm.com> Subject: [PATCH 08/23] mm: Introduce ZAP_FLAG_SKIP_SWAP Firstly, the comment in zap_pte_range() is misleading because it checks against details rather than check_mappings, so it's against what the code did. Meanwhile, it's confusing too on not explaining why passing in the details pointer would mean to skip all swap entries. New user of zap_details could very possibly miss this fact if they don't read deep until zap_pte_range() because there's no comment at zap_details talking about it at all, so swap entries could be errornously skipped without being noticed. This partly reverts 3e8715fdc03e ("mm: drop zap_details::check_swap_entries"), but introduce ZAP_FLAG_SKIP_SWAP flag, which means the opposite of previous "details" parameter: the caller should explicitly set this to skip swap entries, otherwise swap entries will always be considered (which is still the major case here). Cc: Kirill A. Shutemov <kirill@...temov.name> Signed-off-by: Peter Xu <peterx@...hat.com> --- include/linux/mm.h | 12 ++++++++++++ mm/memory.c | 8 +++++--- 2 files changed, 17 insertions(+), 3 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index bb513a346beb..c11fbce0d557 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1704,6 +1704,8 @@ extern void user_shm_unlock(size_t, struct user_struct *); /* Whether to check page->mapping when zapping */ #define ZAP_FLAG_CHECK_MAPPING BIT(0) +/* Whether to skip zapping swap entries */ +#define ZAP_FLAG_SKIP_SWAP BIT(1) /* * Parameter block passed down to zap_pte_range in exceptional cases. @@ -1726,6 +1728,16 @@ zap_check_mapping_skip(struct zap_details *details, struct page *page) return details->zap_mapping != page_rmapping(page); } +/* Return true if skip swap entries, false otherwise */ +static inline bool +zap_skip_swap(struct zap_details *details) +{ + if (!details) + return false; + + return details->zap_flags & ZAP_FLAG_SKIP_SWAP; +} + struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, pte_t pte); struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr, diff --git a/mm/memory.c b/mm/memory.c index 2e540b315481..a02c4d851cd4 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1284,8 +1284,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, continue; } - /* If details->check_mapping, we leave swap entries. */ - if (unlikely(details)) + if (unlikely(zap_skip_swap(details))) continue; if (!non_swap_entry(entry)) @@ -3225,7 +3224,10 @@ void unmap_mapping_pages(struct address_space *mapping, pgoff_t start, pgoff_t nr, bool even_cows) { pgoff_t first_index = start, last_index = start + nr - 1; - struct zap_details details = { .zap_mapping = mapping }; + struct zap_details details = { + .zap_mapping = mapping, + .zap_flags = ZAP_FLAG_SKIP_SWAP, + }; if (!even_cows) details.zap_flags |= ZAP_FLAG_CHECK_MAPPING; -- 2.26.2
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