From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B34CCCA47A for ; Thu, 16 Jun 2022 17:49:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238818AbiFPRtG (ORCPT ); Thu, 16 Jun 2022 13:49:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53716 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237099AbiFPRs4 (ORCPT ); Thu, 16 Jun 2022 13:48:56 -0400 Received: from mail-pj1-x102d.google.com (mail-pj1-x102d.google.com [IPv6:2607:f8b0:4864:20::102d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E09C33ED23 for ; Thu, 16 Jun 2022 10:48:52 -0700 (PDT) Received: by mail-pj1-x102d.google.com with SMTP id o7-20020a17090a0a0700b001ebad897457so1015301pjo.0 for ; Thu, 16 Jun 2022 10:48:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=IVDYrUdqiRm9UcRbpXweUBj4/hDRVoO4CK1KpBPozys=; b=YoZ1bssMZl0ds5wLwIPKg0IItqCPaKU17iyetjJF+hT+7KvhMVimEkgRt95TZkLAxO FnqS18PmPzsWKkIght4RbuqwygilGASy2GLKqKg6k/vzT6t+DtM4UxAQl5b7P9A3TNNf eNO3UdSwBlFGrUig73CtXZrfbbh+sfQ3yu/6CT/tziWSALK5brivuz9r9Oul1PmCzrfZ vwzv81Kzs6hCvJuSzDap1wEz3A/BmNXbZucyPTub2avd33WiHFdjm29e8KsZtbG6Ob56 R8nESRo3DArWhf+2Xo28r7HWLmRlqKlf75OJ1nRX8ig9JYoj6D/6DI+3HTWP9r+gSf7n AW3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=IVDYrUdqiRm9UcRbpXweUBj4/hDRVoO4CK1KpBPozys=; b=fAxnUT3pQhUL/BqM7oEfVsrGILpoB9jRYSJ21l0lmNvFEFvcA34rXWhsW2LOazWNug LltnyDY00IqhsTTtV0e0I9eeCTL8yPgkCrenobQc/W40x4xFSDUc+qqIkr/S3DkA8oIH ecYp7aWV6KSDnlchfDPiGWDYuEUdklvqS/MI7AreFY+a4irJofgsBEHQPSQm/FQ6LM/Z gAm9rLRHeg10dHeDR1cRQxJl667cM3f8c12OTTOY+XTQjHM/ntfaNRux9PThXyCxhp/C sQsG5YCYubz0Ek9tX8hnf5BySHhFUqAhNZwaQHNzgQMTWkoHXRxG7f3cPIy9jX1DYZFI w1hQ== X-Gm-Message-State: AJIora8IHb2PHcKkV7PxZMv+JWN9DMkoHUQ99r0Wa83k3rMer2WU8agg H4a5T2h0iBzuGrQmkzDWl0Q= X-Google-Smtp-Source: AGRyM1vxGK17GWzftPYeur/8Me6GEPOXRVJXvmUbi9GWcVUiu6WhWb2FJDsYzyvI0N7smHaYh/uyEg== X-Received: by 2002:a17:902:c403:b0:167:4a9f:2799 with SMTP id k3-20020a170902c40300b001674a9f2799mr5716030plk.56.1655401732435; Thu, 16 Jun 2022 10:48:52 -0700 (PDT) Received: from localhost.localdomain (c-67-174-241-145.hsd1.ca.comcast.net. [67.174.241.145]) by smtp.gmail.com with ESMTPSA id z21-20020a17090a8b9500b001e8520b211bsm1818289pjn.53.2022.06.16.10.48.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Jun 2022 10:48:51 -0700 (PDT) From: Yang Shi To: vbabka@suse.cz, kirill.shutemov@linux.intel.com, willy@infradead.org, zokeefe@google.com, linmiaohe@huawei.com, akpm@linux-foundation.org Cc: shy828301@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [v5 PATCH 3/7] mm: khugepaged: better comments for anon vma check in hugepage_vma_revalidate Date: Thu, 16 Jun 2022 10:48:36 -0700 Message-Id: <20220616174840.1202070-4-shy828301@gmail.com> X-Mailer: git-send-email 2.26.3 In-Reply-To: <20220616174840.1202070-1-shy828301@gmail.com> References: <20220616174840.1202070-1-shy828301@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The hugepage_vma_revalidate() needs to check if the vma is still anonymous vma or not since the address may be unmapped then remapped to file before khugepaged reaquired the mmap_lock. The old comment is not quite helpful, elaborate this with better comment. Reviewed-by: Zach O'Keefe Signed-off-by: Yang Shi --- mm/khugepaged.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index db0b334a7d1f..5baa394e34c8 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -960,7 +960,13 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, return SCAN_ADDRESS_RANGE; if (!hugepage_vma_check(vma, vma->vm_flags)) return SCAN_VMA_CHECK; - /* Anon VMA expected */ + /* + * Anon VMA expected, the address may be unmapped then + * remapped to file after khugepaged reaquired the mmap_lock. + * + * hugepage_vma_check may return true for qualified file + * vmas. + */ if (!vma->anon_vma || !vma_is_anonymous(vma)) return SCAN_VMA_CHECK; return 0; -- 2.26.3