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[184.145.104.227]) by smtp.gmail.com with ESMTPSA id v66sm3103621qkd.113.2021.04.27.09.13.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Apr 2021 09:13:34 -0700 (PDT) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Nadav Amit , Miaohe Lin , Mike Rapoport , Andrea Arcangeli , Hugh Dickins , peterx@redhat.com, Jerome Glisse , Mike Kravetz , Jason Gunthorpe , Matthew Wilcox , Andrew Morton , Axel Rasmussen , "Kirill A . Shutemov" Subject: [PATCH v2 08/24] mm: Introduce ZAP_FLAG_SKIP_SWAP Date: Tue, 27 Apr 2021 12:13:01 -0400 Message-Id: <20210427161317.50682-9-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210427161317.50682-1-peterx@redhat.com> References: <20210427161317.50682-1-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 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 39c944bf7ed3a..2227e9107e53e 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 94954436544f7..5325c1c2cbd78 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)) @@ -3236,7 +3235,10 @@ 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