From patchwork Tue May 25 16:21:44 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yang Shi X-Patchwork-Id: 12279539 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.5 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A18E1C2B9F8 for ; Tue, 25 May 2021 16:21:50 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 49E166140E for ; Tue, 25 May 2021 16:21:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 49E166140E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CE73A6B0036; Tue, 25 May 2021 12:21:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C6FE06B006E; Tue, 25 May 2021 12:21:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A9AA06B0070; Tue, 25 May 2021 12:21:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0232.hostedemail.com [216.40.44.232]) by kanga.kvack.org (Postfix) with ESMTP id 745B36B0036 for ; Tue, 25 May 2021 12:21:49 -0400 (EDT) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 0E8A59084 for ; Tue, 25 May 2021 16:21:49 +0000 (UTC) X-FDA: 78180269538.12.8F5732B Received: from mail-pl1-f176.google.com (mail-pl1-f176.google.com [209.85.214.176]) by imf17.hostedemail.com (Postfix) with ESMTP id BC4B940002FF for ; Tue, 25 May 2021 16:21:44 +0000 (UTC) Received: by mail-pl1-f176.google.com with SMTP id a7so7917656plh.3 for ; Tue, 25 May 2021 09:21:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=LV7x92f0QnEOEbD+UIPivGRGEvqdiDitTjQ43vOV6Fc=; b=c1YciXiw1HnElOZummb+oM3cKQ24xEv/oBVCKgZ8FIAUmStJnIcisIMq4Nw4xw3pzz leczUPKeuCxPhrzailBKqECLgtLYdyygH9FivuzofzDiWn34X3J8mriQHlgEjU/2ASXJ 9hvB1RVG2EpOyYBq9CM9wC6NEPre19ycooEiHClk6WO+xHkzm3zPBXdanYwoGNxilukX gwdj7IQ1Bqvkwk2hUa1k3HfzQ/fTnowEwoDY1RBhyN++y1E8xOOm+aZS+kJP0/yHTp3z doR0l4Y7WFG47WgpI0P0DA4Q+nsB0sfCtLMpeQiv62HE10B5BvNHnrGabg/NQK4lcOFh Pw/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=LV7x92f0QnEOEbD+UIPivGRGEvqdiDitTjQ43vOV6Fc=; b=eiCY2WDFK4BPgHo7oUrly2KfszFz8EO7nsqVlk3vNh+5wW6d5zxviY2U1oTsJxEEUg 26S5498OchWjK7F7jrKL/2lVR0bU+KU6ajEJ1PaILtQCxSJj5WGsIFMF+W/HfJ3Fno1T h+k+wYBgmaiakBGQhU0fsIiwD29Hb4OUzkKLopI3elrkAm4eBu4RBws/7Ms4grUkDD3Z i2MDyWboodXPL3a7KJO7Z1SQX2KsWJWTpB5EVgSsYIjoI02LW30bUl9dnusKizKncOGB sGpAw0JOhpv043Yqk1tu55gj8OSk4ToJY63HxrEFvEa5bRqV00dWZqyTgDuYbJTMwrbr iJOA== X-Gm-Message-State: AOAM531+2MQg2FMOMD5duSv3Q+BxejbALGtY7jKKnrbVD28Hzo08iKdw qDOGO2ABYehHVQhSDbJtcyA= X-Google-Smtp-Source: ABdhPJz+dQWuMdya3EF4zCIsGQlzFDX+GPDVbAj3bBG3Wzyu8poC1aLTK4pi08x3qZkbWzbZMyPyJw== X-Received: by 2002:a17:90a:d0c5:: with SMTP id y5mr31056828pjw.109.1621959707704; Tue, 25 May 2021 09:21:47 -0700 (PDT) Received: from localhost.localdomain (c-73-93-239-127.hsd1.ca.comcast.net. [73.93.239.127]) by smtp.gmail.com with ESMTPSA id e22sm7493087pfl.188.2021.05.25.09.21.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 May 2021 09:21:47 -0700 (PDT) From: Yang Shi To: hughd@google.com, ziy@nvidia.com, kirill.shutemov@linux.intel.com, naoya.horiguchi@nec.com, wangyugui@e16-tech.com, akpm@linux-foundation.org Cc: shy828301@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [v3 PATCH 1/2] mm: rmap: make try_to_unmap() void function Date: Tue, 25 May 2021 09:21:44 -0700 Message-Id: <20210525162145.3510-1-shy828301@gmail.com> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 X-Rspamd-Queue-Id: BC4B940002FF Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=c1YciXiw; spf=pass (imf17.hostedemail.com: domain of shy828301@gmail.com designates 209.85.214.176 as permitted sender) smtp.mailfrom=shy828301@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam04 X-Stat-Signature: fi5arydhmkurgy7ciowrg9zr7i83axw4 X-HE-Tag: 1621959704-867274 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Currently try_to_unmap() return bool value by checking page_mapcount(), however this may return false positive since page_mapcount() doesn't check all subpages of compound page. The total_mapcount() could be used instead, but its cost is higher since it traverses all subpages. Actually the most callers of try_to_unmap() don't care about the return value at all. So just need check if page is still mapped by page_mapped() when necessary. And page_mapped() does bail out early when it finds mapped subpage. Suggested-by: Hugh Dickins Signed-off-by: Yang Shi Acked-by: Hugh Dickins --- include/linux/rmap.h | 2 +- mm/huge_memory.c | 4 +--- mm/memory-failure.c | 13 ++++++------- mm/rmap.c | 6 +----- mm/vmscan.c | 3 ++- 5 files changed, 11 insertions(+), 17 deletions(-) diff --git a/include/linux/rmap.h b/include/linux/rmap.h index def5c62c93b3..116cb193110a 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -194,7 +194,7 @@ static inline void page_dup_rmap(struct page *page, bool compound) int page_referenced(struct page *, int is_locked, struct mem_cgroup *memcg, unsigned long *vm_flags); -bool try_to_unmap(struct page *, enum ttu_flags flags); +void try_to_unmap(struct page *, enum ttu_flags flags); /* Avoid racy checks */ #define PVMW_SYNC (1 << 0) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 19195fca1aee..80fe642d742d 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2336,15 +2336,13 @@ static void unmap_page(struct page *page) { enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD; - bool unmap_success; VM_BUG_ON_PAGE(!PageHead(page), page); if (PageAnon(page)) ttu_flags |= TTU_SPLIT_FREEZE; - unmap_success = try_to_unmap(page, ttu_flags); - VM_BUG_ON_PAGE(!unmap_success, page); + try_to_unmap(page, ttu_flags); } static void remap_page(struct page *page, unsigned int nr) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 9dcc9bcea731..6dd53ff34825 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1126,7 +1126,7 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn, collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED); if (!PageHuge(hpage)) { - unmap_success = try_to_unmap(hpage, ttu); + try_to_unmap(hpage, ttu); } else { if (!PageAnon(hpage)) { /* @@ -1138,17 +1138,16 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn, */ mapping = hugetlb_page_mapping_lock_write(hpage); if (mapping) { - unmap_success = try_to_unmap(hpage, - ttu|TTU_RMAP_LOCKED); + try_to_unmap(hpage, ttu|TTU_RMAP_LOCKED); i_mmap_unlock_write(mapping); - } else { + } else pr_info("Memory failure: %#lx: could not lock mapping for mapped huge page\n", pfn); - unmap_success = false; - } } else { - unmap_success = try_to_unmap(hpage, ttu); + try_to_unmap(hpage, ttu); } } + + unmap_success = !page_mapped(hpage); if (!unmap_success) pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n", pfn, page_mapcount(hpage)); diff --git a/mm/rmap.c b/mm/rmap.c index a35cbbbded0d..728de421e43a 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1748,10 +1748,8 @@ static int page_not_mapped(struct page *page) * * Tries to remove all the page table entries which are mapping this * page, used in the pageout path. Caller must hold the page lock. - * - * If unmap is successful, return true. Otherwise, false. */ -bool try_to_unmap(struct page *page, enum ttu_flags flags) +void try_to_unmap(struct page *page, enum ttu_flags flags) { struct rmap_walk_control rwc = { .rmap_one = try_to_unmap_one, @@ -1776,8 +1774,6 @@ bool try_to_unmap(struct page *page, enum ttu_flags flags) rmap_walk_locked(page, &rwc); else rmap_walk(page, &rwc); - - return !page_mapcount(page) ? true : false; } /** diff --git a/mm/vmscan.c b/mm/vmscan.c index f96d62159720..fa5052ace415 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1499,7 +1499,8 @@ static unsigned int shrink_page_list(struct list_head *page_list, if (unlikely(PageTransHuge(page))) flags |= TTU_SPLIT_HUGE_PMD; - if (!try_to_unmap(page, flags)) { + try_to_unmap(page, flags); + if (page_mapped(page)) { stat->nr_unmap_fail += nr_pages; if (!was_swapbacked && PageSwapBacked(page)) stat->nr_lazyfree_fail += nr_pages; From patchwork Tue May 25 16:21:45 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yang Shi X-Patchwork-Id: 12279541 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.5 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7DD49C47085 for ; Tue, 25 May 2021 16:21:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 19681611C2 for ; Tue, 25 May 2021 16:21:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 19681611C2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AEA866B006E; Tue, 25 May 2021 12:21:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A4DBF6B0070; Tue, 25 May 2021 12:21:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8796D6B0071; Tue, 25 May 2021 12:21:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0091.hostedemail.com [216.40.44.91]) by kanga.kvack.org (Postfix) with ESMTP id 542446B006E for ; Tue, 25 May 2021 12:21:51 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id E4C76180AD802 for ; Tue, 25 May 2021 16:21:50 +0000 (UTC) X-FDA: 78180269580.14.34B5AFB Received: from mail-pf1-f182.google.com (mail-pf1-f182.google.com [209.85.210.182]) by imf29.hostedemail.com (Postfix) with ESMTP id 642202D5 for ; Tue, 25 May 2021 16:21:42 +0000 (UTC) Received: by mail-pf1-f182.google.com with SMTP id p39so7657326pfw.8 for ; Tue, 25 May 2021 09:21:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=mmbfHX6D035LsGn/+TcBmTVxPxWKc+RU4GxB9gPvNc0=; b=IgD5NSBRENJweCx2RLe1CXOfi7EWjfiRlHMOcLL++sy/kQIz927Jj8uzD77JqyRk/X wl62ZGgBLGWDquk3BC9ihn3gqeROxDwRp+ZcAQBG4OBrZHWXd03Af64wKenlWn1SkHeU 7a2yKbWoI2HLl2szycw5511ry5UQFsjAsEkgS9Em0owXtRomOsLrXG3dkMRklI2OTbCT vtu/YMFmK2zDW/x3aw9TPvvRl4ay3ucK9/zI9mOK8fPG3Wmy3nVc/etpib3MTJhIxbnq XqaINJd4BoUcCQ3n8xs6Uy9w2B1oIYhgYmmsq2tyy3Pc1sYzIGS7CvKxltKrdZaG3M1x OcVg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=mmbfHX6D035LsGn/+TcBmTVxPxWKc+RU4GxB9gPvNc0=; b=fvRKChlRboDwN89wLHjZbn+bZGWDvxoUUwfNhvryxJ2LuFOz3dauRn3O65UuESO7ya YF6PzxCisSAneST5/RQ2bQiz9wPSzTJmFbdvnb2H88ie9cHKLLnrKN//4dwXL9Rc17mS Tx0qRdwPi7KdSM32WH8nUZ5lqRTNnWcI4FtcTRGW2s20e+18f9yLKzyNCCOgQ/rsuAB9 7X6o9D+LzcE4alnveW3uu3k0mz7F23QoIm87rjYFLUzcXy5nMK2JxCjOS/EqAJCelhjS Kgc/DIHDspbJT+moCG4Nv4vXtQnBBudPwsM7aV3XOTH+vjmfC/39xOjJ4nW1G2yYtpl6 tCLg== X-Gm-Message-State: AOAM530Uvxr1u/M+qEu9biNtDHtnd2QD3nBpSc6+TSsriVODwX4OlVwm uHLqoksAa7IP6obIMxRgaxc= X-Google-Smtp-Source: ABdhPJy88yigkedUoFzoMFNJUDnuErEK45jOVUAaZulsIcyoFD5pW9mFqhZnTE0rj8HURvbS/a7tDA== X-Received: by 2002:a63:5a01:: with SMTP id o1mr19485648pgb.313.1621959709715; Tue, 25 May 2021 09:21:49 -0700 (PDT) Received: from localhost.localdomain (c-73-93-239-127.hsd1.ca.comcast.net. [73.93.239.127]) by smtp.gmail.com with ESMTPSA id e22sm7493087pfl.188.2021.05.25.09.21.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 May 2021 09:21:48 -0700 (PDT) From: Yang Shi To: hughd@google.com, ziy@nvidia.com, kirill.shutemov@linux.intel.com, naoya.horiguchi@nec.com, wangyugui@e16-tech.com, akpm@linux-foundation.org Cc: shy828301@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [v3 PATCH 2/2] mm: thp: check page_mapped instead of page_mapcount for split Date: Tue, 25 May 2021 09:21:45 -0700 Message-Id: <20210525162145.3510-2-shy828301@gmail.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210525162145.3510-1-shy828301@gmail.com> References: <20210525162145.3510-1-shy828301@gmail.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: 642202D5 Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=IgD5NSBR; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf29.hostedemail.com: domain of shy828301@gmail.com designates 209.85.210.182 as permitted sender) smtp.mailfrom=shy828301@gmail.com X-Rspamd-Server: rspam03 X-Stat-Signature: uug5ugokeh1g4icdp1pxw8w6jafu8iob X-HE-Tag: 1621959702-674846 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: When debugging the bug reported by Wang Yugui [1], try_to_unmap() may return false positive for PTE-mapped THP since page_mapcount() is used to check if the THP is unmapped, but it just checks compound mapount and head page's mapcount. If the THP is PTE-mapped and head page is not mapped, it may return false positive. The try_to_unmap() has been changed to void function, so check page_mapped() after it. And changed BUG_ON to WARN_ON since it is not a fatal issue. [1] https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/ Reviewed-by: Zi Yan Signed-off-by: Yang Shi --- v3: Incorporated the comments from Hugh. Keep Zi Yan's reviewed-by tag since there is no fundamental change against v2. v2: Removed dead code and updated the comment of try_to_unmap() per Zi Yan. mm/huge_memory.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 80fe642d742d..72d81d8e01b1 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2343,6 +2343,8 @@ static void unmap_page(struct page *page) ttu_flags |= TTU_SPLIT_FREEZE; try_to_unmap(page, ttu_flags); + + VM_WARN_ON_ONCE_PAGE(page_mapped(page), page); } static void remap_page(struct page *page, unsigned int nr) @@ -2653,7 +2655,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) struct deferred_split *ds_queue = get_deferred_split_queue(head); struct anon_vma *anon_vma = NULL; struct address_space *mapping = NULL; - int count, mapcount, extra_pins, ret; + int mapcount, extra_pins, ret; pgoff_t end; VM_BUG_ON_PAGE(is_huge_zero_page(head), head); @@ -2712,7 +2714,6 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) } unmap_page(head); - VM_BUG_ON_PAGE(compound_mapcount(head), head); /* block interrupt reentry in xa_lock and spinlock */ local_irq_disable(); @@ -2730,7 +2731,6 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) /* Prevent deferred_split_scan() touching ->_refcount */ spin_lock(&ds_queue->split_queue_lock); - count = page_count(head); mapcount = total_mapcount(head); if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) { if (!list_empty(page_deferred_list(head))) { @@ -2752,16 +2752,9 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) __split_huge_page(page, list, end); ret = 0; } else { - if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { - pr_alert("total_mapcount: %u, page_count(): %u\n", - mapcount, count); - if (PageTail(page)) - dump_page(head, NULL); - dump_page(page, "total_mapcount(head) > 0"); - BUG(); - } spin_unlock(&ds_queue->split_queue_lock); -fail: if (mapping) +fail: + if (mapping) xa_unlock(&mapping->i_pages); local_irq_enable(); remap_page(head, thp_nr_pages(head));