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 X-Spam-Level: X-Spam-Status: No, score=-6.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 41739C31E45 for ; Thu, 13 Jun 2019 20:32:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CC3C821537 for ; Thu, 13 Jun 2019 20:32:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="mh0Rc495" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CC3C821537 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 4F17C8E0001; Thu, 13 Jun 2019 16:32:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4A2636B000C; Thu, 13 Jun 2019 16:32:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3B6DC8E0001; Thu, 13 Jun 2019 16:32:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-vs1-f72.google.com (mail-vs1-f72.google.com [209.85.217.72]) by kanga.kvack.org (Postfix) with ESMTP id 14E2A6B000A for ; Thu, 13 Jun 2019 16:32:44 -0400 (EDT) Received: by mail-vs1-f72.google.com with SMTP id x22so85869vsj.1 for ; Thu, 13 Jun 2019 13:32:44 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:mime-version:references :in-reply-to:from:date:message-id:subject:to:cc; bh=XnwdqEB/zxSUoi8AX3TTUKJIQzqvpn/EDnWBDbRAeC0=; b=e9adcK5/bJ1Efv9aMgwbmthfqKhyWxe7XpxxfW8dWEXPcwi5d6vhkVxf9BpoODnCP3 muSloVlqni/MLnDJG/Mr6LJerBN94c2updGRju11WmYG3bQ2QDVsI7N9DtUgcY7TPtWc FltsRBO/AoXKSP+HM3IETjObH2THrbdk7lkBcqM65uxmBl3FVgcgd5bM+I/aav+xPI8q FHXZJyIpJ8idnSNuJ5VsdueiP/RpLANUbr0zROfooH7H2Uup7tVedNAYSG5ucW+ih/UR eoGbU99LJi/BcTbVETUzWmTrc6e44bu953GSU7ayrW4YTBtirShRpq+LtDdE6zQlXycr ho8w== X-Gm-Message-State: APjAAAUp4EJT648+fHfMnKV8ySLgBvXa0K17ytSn+jT7WVmpPMf/IPTh EOoOXPY2WGN4DFPrRBaNGAH1L2Oc8zo6dpsDTXNKrXi1vEyDc+Guh88H/HUAQXfMSsoAvbgiIBw olOVy5NpTgYZmqm7oPOFCLvNjTR7nfShjmKxxWS2af51sUiuOyIHtzrzO9VmQjiG+0g== X-Received: by 2002:a67:7fd8:: with SMTP id a207mr27154946vsd.85.1560457963752; Thu, 13 Jun 2019 13:32:43 -0700 (PDT) X-Received: by 2002:a67:7fd8:: with SMTP id a207mr27154874vsd.85.1560457963037; Thu, 13 Jun 2019 13:32:43 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1560457963; cv=none; d=google.com; s=arc-20160816; b=wRa+RlikDbPElWKrzlmplfvs7pkhWvV6BmkggAmCsq7BOUp7Gm7Zpy8tCTeHC02u6H tvSWTIkiJo27+/pcaa5YwS1b4jMVOA1BXrXCMyDUiMDdHI9f9Su3x5WjtTrbByEh4Yg8 FHXpuLLJ2cgS8dZ/Ssd7yCfQd6cidQQcfdCo01JMwCY8p1yT246epDEY5L2FKafB3G44 sPVd5cr7owCTKUDz/2XJoE7aBMkoGPrCgpmMFtIcwEYDLaTbHvkY55JmzvXuKVNpGGMc ZE/yUBU7znIcbAPdgs+uOx4guGAGvipEMxG8LdBCbcWrLynYgiEOMhEXQl2g9TLAyTdx mH5w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:dkim-signature; bh=XnwdqEB/zxSUoi8AX3TTUKJIQzqvpn/EDnWBDbRAeC0=; b=M5pvb8YjBWxp6jUtnDIYZvG6gD1Rf1W6xE9caXooYyIm1MiFAv7KROSOQAL9MaE9cs oXll8Mnj3tm0l1Pr0iTrOHOblXlTamwcEzM9Z0g6T+4BUS80o1V+gZm/KhkhGF+KaOuR MqVJTvi88k2qCkNl7DKJzaEEb2OpLj6Vofzod4Xjg/CkdpUPyVwxBzTjW1fO5TV0nsbF VId5hHuDOSrvRE/LU1Ra2kG2QOCxHDsc/NjQQeAeahjht6UFHO9ILm0ce9YhaoZAoOgS 98k5IDzPsH/Nx4AdQqJ226dpvZbYtsfYlHTsprwAKmpMRG2YCU2yO2Ryyut0J9IgPm/k oVTA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=mh0Rc495; spf=pass (google.com: domain of avagin@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=avagin@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id h29sor343202uab.62.2019.06.13.13.32.42 for (Google Transport Security); Thu, 13 Jun 2019 13:32:43 -0700 (PDT) Received-SPF: pass (google.com: domain of avagin@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=mh0Rc495; spf=pass (google.com: domain of avagin@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=avagin@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=XnwdqEB/zxSUoi8AX3TTUKJIQzqvpn/EDnWBDbRAeC0=; b=mh0Rc495xOBUVTnnEmr4AY5NBwVSaqzX7zqV6Dc0pZhAdBBMh97ij8pz/2/iyufp6F ooJ45PQgHYRytRZez//z7awy8/LfcteuyU4iQPzoIaxepq7w2liWukbsUhe7AVsGV2m4 cGRVK2X2wHvYVrnO3N3b1vRlOqgAy1SA4v+7JmfMJIywOp9HK3ygvJWCv7tbo6q745j4 w7aNSUQU4VPwQ+rzdjFOPSxICgPxP25z9gSYvI9Fr4DHolTZx7l7s1QyHkMnZG2KUxWG 2/hwjxPew43xbKjCW3en5tfPSloSM/x9hxBFVQ0j+Y7gNVoK1FrgVaKF+OIkIdmaZH4p Ua2A== X-Google-Smtp-Source: APXvYqwYSC5celn0/YY56qS1Ya7QSTRLAhhjVJF5SlLdd0JuZboIS3qB8YqgOjoOCvVdt0mtU6tXdL4lZWb7/Se6XdM= X-Received: by 2002:ab0:6619:: with SMTP id r25mr3232042uam.33.1560457962568; Thu, 13 Jun 2019 13:32:42 -0700 (PDT) MIME-Version: 1.0 References: <156007465229.3335.10259979070641486905.stgit@buzz> <156007493995.3335.9595044802115356911.stgit@buzz> <20190612231426.GA3639@gmail.com> In-Reply-To: From: Andrei Vagin Date: Thu, 13 Jun 2019 13:32:31 -0700 Message-ID: Subject: Re: [PATCH v2 5/6] proc: use down_read_killable mmap_sem for /proc/pid/map_files To: Konstantin Khlebnikov Cc: linux-mm@kvack.org, Andrew Morton , LKML , Oleg Nesterov , Matthew Wilcox , Michal Hocko , Cyrill Gorcunov , Kirill Tkhai , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Al Viro , Roman Gushchin , Dmitry Safonov , Mike Rapoport Content-Type: text/plain; charset="UTF-8" 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: On Thu, Jun 13, 2019 at 1:15 AM Konstantin Khlebnikov wrote: > > On 13.06.2019 2:14, Andrei Vagin wrote: > > On Sun, Jun 09, 2019 at 01:09:00PM +0300, Konstantin Khlebnikov wrote: > >> Do not stuck forever if something wrong. > >> Killable lock allows to cleanup stuck tasks and simplifies investigation. > > > > This patch breaks the CRIU project, because stat() returns EINTR instead > > of ENOENT: > > > > [root@fc24 criu]# stat /proc/self/map_files/0-0 > > stat: cannot stat '/proc/self/map_files/0-0': Interrupted system call > > Good catch. > > It seems CRIU tests has good coverage for darkest corners of kernel API. > Kernel CI projects should use it. I suppose you know how to promote this. =) I remember Mike was trying to add the CRIU test suite into kernel-ci, but it looks like this ended up with nothing. The good thing here is that we have our own kernel-ci: https://travis-ci.org/avagin/linux/builds Travis-CI doesn't allow to replace the kernel, so we use CRIU to dump/restore a ssh session and travis doesn't notice when we kexec a new kernel. > > > > > Here is one inline comment with the fix for this issue. > > > >> > >> It seems ->d_revalidate() could return any error (except ECHILD) to > >> abort validation and pass error as result of lookup sequence. > >> > >> Signed-off-by: Konstantin Khlebnikov > >> Reviewed-by: Roman Gushchin > >> Reviewed-by: Cyrill Gorcunov > >> Reviewed-by: Kirill Tkhai > > > > It was nice to see all four of you in one place :). > > > >> Acked-by: Michal Hocko > >> --- > >> fs/proc/base.c | 27 +++++++++++++++++++++------ > >> 1 file changed, 21 insertions(+), 6 deletions(-) > >> > >> diff --git a/fs/proc/base.c b/fs/proc/base.c > >> index 9c8ca6cd3ce4..515ab29c2adf 100644 > >> --- a/fs/proc/base.c > >> +++ b/fs/proc/base.c > >> @@ -1962,9 +1962,12 @@ static int map_files_d_revalidate(struct dentry *dentry, unsigned int flags) > >> goto out; > >> > >> if (!dname_to_vma_addr(dentry, &vm_start, &vm_end)) { > >> - down_read(&mm->mmap_sem); > >> - exact_vma_exists = !!find_exact_vma(mm, vm_start, vm_end); > >> - up_read(&mm->mmap_sem); > >> + status = down_read_killable(&mm->mmap_sem); > >> + if (!status) { > >> + exact_vma_exists = !!find_exact_vma(mm, vm_start, > >> + vm_end); > >> + up_read(&mm->mmap_sem); > >> + } > >> } > >> > >> mmput(mm); > >> @@ -2010,8 +2013,11 @@ static int map_files_get_link(struct dentry *dentry, struct path *path) > >> if (rc) > >> goto out_mmput; > >> > >> + rc = down_read_killable(&mm->mmap_sem); > >> + if (rc) > >> + goto out_mmput; > >> + > >> rc = -ENOENT; > >> - down_read(&mm->mmap_sem); > >> vma = find_exact_vma(mm, vm_start, vm_end); > >> if (vma && vma->vm_file) { > >> *path = vma->vm_file->f_path; > >> @@ -2107,7 +2113,10 @@ static struct dentry *proc_map_files_lookup(struct inode *dir, > >> if (!mm) > >> goto out_put_task; > >> > >> - down_read(&mm->mmap_sem); > >> + result = ERR_PTR(-EINTR); > >> + if (down_read_killable(&mm->mmap_sem)) > >> + goto out_put_mm; > >> + > > > > result = ERR_PTR(-ENOENT); > > > >> vma = find_exact_vma(mm, vm_start, vm_end); > >> if (!vma) > >> goto out_no_vma; > >> @@ -2118,6 +2127,7 @@ static struct dentry *proc_map_files_lookup(struct inode *dir, > >> > >> out_no_vma: > >> up_read(&mm->mmap_sem); > >> +out_put_mm: > >> mmput(mm); > >> out_put_task: > >> put_task_struct(task); > >> @@ -2160,7 +2170,12 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx) > >> mm = get_task_mm(task); > >> if (!mm) > >> goto out_put_task; > >> - down_read(&mm->mmap_sem); > >> + > >> + ret = down_read_killable(&mm->mmap_sem); > >> + if (ret) { > >> + mmput(mm); > >> + goto out_put_task; > >> + } > >> > >> nr_files = 0; > >>