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[23.128.96.18]) by mx.google.com with ESMTP id eb8si4586943ejc.355.2021.10.04.12.11.28; Mon, 04 Oct 2021 12:11:59 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20210112 header.b=ED7KbLk3; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238618AbhJDSat (ORCPT + 99 others); Mon, 4 Oct 2021 14:30:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50970 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238617AbhJDSas (ORCPT ); Mon, 4 Oct 2021 14:30:48 -0400 Received: from mail-ed1-x535.google.com (mail-ed1-x535.google.com [IPv6:2a00:1450:4864:20::535]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CEA6CC061745 for ; Mon, 4 Oct 2021 11:28:58 -0700 (PDT) Received: by mail-ed1-x535.google.com with SMTP id g8so68559440edt.7 for ; Mon, 04 Oct 2021 11:28:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=M3olL4PCIPnsY+XsG6ODxFPkLeYPL3IXmw45N+fdrVs=; b=ED7KbLk3Ph78YVcabHLJMRc846iOZ2dIMnZRnR0e6vJ6SPDEhonEpbqT45rC+8p5Ut XVAKBqPSzdcfcuSk1x6uebAiWCa2qDhAoXKI2O0qQ4eGJmD70AVvl1Ykkol5hMNsc24D 9MfEvtlJaFfoct2c6/g7z2+rFYCBRR2moM+b8I51aXJU6AKxj/0V/yAgDx3XcvaAj08H dVGjtX8QraZx4uew81Xi+V4Z+ClwKzncibSDMq6OanS1R3oSGB5l1ZIssPTEcr4uvsoR jiAfJZAi4vGd8bK+fZaNi+FyiIz9XNjyeGOt6h+6a9/BpBhSINdXk1qQ//7ZRpyUqQ+u J2YQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=M3olL4PCIPnsY+XsG6ODxFPkLeYPL3IXmw45N+fdrVs=; b=N+vYsP/kNq9pfJhuHZPOwAnBfSZdWXAX2Qh7RmERV9OesLkTCHErHGgGEq8clKRKEB Q9J5DgLpYEGmByAO5nUDxjIQRCYmIsTGkofTLJeBCubt6y9H6X113V+dU6GnBbZh/YpN G1D0dRIfyO7b7fdD/TPPjjMLN8ANC1UBk0VGNvMqMqr3ugqxSBDfOVAXTWcVzkGQHq2g kqDOTX/tAo5XCKiDsJb3z6QLPKB48VXL4NFmvChhnhbr9tDq4dyKbnVD5bXHVg5qzf6M aR2WSIGrrXmpjI69o4vMhFLX8aZyjAQcvQG7jjTYLuQjwVALtF3ScFNtnkqxJJ2pWW1K nR/Q== X-Gm-Message-State: AOAM530tOC8yJCrsg3+r0BBku9z59kMMuTwgwJKgFdJHGBmpbKRijBtn HfV0WQyJehjLYLnmwnicnz7woZCimOkze1XRUce+IjMDKv4= X-Received: by 2002:a50:8d85:: with SMTP id r5mr19954555edh.312.1633372137470; Mon, 04 Oct 2021 11:28:57 -0700 (PDT) MIME-Version: 1.0 References: <67906bf5-4de9-8433-3d70-cc8fc5cc2347@linux.alibaba.com> <3d264ed9-f8fd-60d4-7125-f9f745ebeb52@google.com> In-Reply-To: From: Yang Shi Date: Mon, 4 Oct 2021 11:28:45 -0700 Message-ID: Subject: Re: [PATCH v2 1/2] mm, thp: check page mapping when truncating page cache To: Matthew Wilcox Cc: Hugh Dickins , Song Liu , Rongwei Wang , Andrew Morton , Linux MM , Linux Kernel Mailing List , William Kucharski Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 2, 2021 at 10:09 AM Matthew Wilcox wrote: > > On Thu, Sep 30, 2021 at 10:39:14AM -0700, Yang Shi wrote: > > On Thu, Sep 30, 2021 at 9:49 AM Hugh Dickins wrote: > > > I assume you're thinking of one of the fuzzer blkdev ones: > > > https://lore.kernel.org/linux-mm/CACkBjsbtF_peC7N_4mRfHML_BeiPe+O9DahTfr84puSG_J9rcQ@mail.gmail.com/ > > > or > > > https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@mail.gmail.com/ > > > > > > I haven't started on those ones yet: yes, I imagine one or both of those > > > will need a further fix (S_ISREG() check somewhere if we're lucky; but > > > could well be nastier); but for the bug in this thread, I expect > > > > Makes sense to me. We should be able to check S_ISREG() in khugepaged, > > if it is not a regular file, just bail out. Sounds not that nasty to > > me AFAIU. > > I don't see why we should have an S_ISREG() check. I agree it's not the > intended usecase, but it ought to work fine. Unless there's something > I'm missing? Check out this bug report: https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@mail.gmail.com/ and the patch from me: https://lore.kernel.org/linux-mm/20210917205731.262693-1-shy828301@gmail.com/ I don't think we handle buffers correctly for file THP, right? My patch is ad hoc, so I thought Hugh's suggestion makes some sense to me. Why do we have THP collapsed for unintended usecase in the first place?