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[184.144.111.238]) by smtp.gmail.com with ESMTPSA id p64sm2915206qka.114.2021.07.15.13.14.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Jul 2021 13:14:42 -0700 (PDT) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Jason Gunthorpe , Mike Kravetz , David Hildenbrand , Alistair Popple , Matthew Wilcox , "Kirill A . Shutemov" , Hugh Dickins , Tiberiu Georgescu , Andrea Arcangeli , Axel Rasmussen , Nadav Amit , Mike Rapoport , Jerome Glisse , Andrew Morton , Miaohe Lin , peterx@redhat.com Subject: [PATCH v5 09/26] mm: Introduce ZAP_FLAG_SKIP_SWAP Date: Thu, 15 Jul 2021 16:14:05 -0400 Message-Id: <20210715201422.211004-10-peterx@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210715201422.211004-1-peterx@redhat.com> References: <20210715201422.211004-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Reviewed-by: Alistair Popple Signed-off-by: Peter Xu --- 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 26088174daab..62a75e4414e3 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1717,6 +1717,8 @@ extern void user_shm_unlock(size_t, struct ucounts *); /* 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. @@ -1740,6 +1742,16 @@ zap_skip_check_mapping(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 2a5a6650f069..d6b1adbf29e4 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1379,8 +1379,7 @@ 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)) @@ -3379,7 +3378,10 @@ 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; -- 2.31.1