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=-8.1 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,USER_AGENT_MUTT autolearn=unavailable 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 EEBD3C31E45 for ; Thu, 13 Jun 2019 17:02:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC8D42063F for ; Thu, 13 Jun 2019 17:02:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="EswV1nGC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727236AbfFMRCX (ORCPT ); Thu, 13 Jun 2019 13:02:23 -0400 Received: from mail-pl1-f196.google.com ([209.85.214.196]:36206 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729522AbfFLXOb (ORCPT ); Wed, 12 Jun 2019 19:14:31 -0400 Received: by mail-pl1-f196.google.com with SMTP id d21so7244328plr.3 for ; Wed, 12 Jun 2019 16:14:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=zENyOoOSgI8QfaggquPMfPbLKw7a6eUv2Qjm9NWJtcQ=; b=EswV1nGCdvSMNN+Ssd1h7rS3RXzjTfEdTIdOLjAh5nTRd36k1bdXI6zWruRLqObK0d gsC+6WcEPSp6FesMM+ciJCWrwUt+f3/TlPdj8OHr1gJIlaqypHatFu/fEtZyZqtTgxf/ 7MmVJ24TsNjxF3L2qzae4mJRJIWKsdAgvTDM41obh31wU5DHCFOSTfiDeRVan1EyTWT2 FA4K03WJSZqhv2G4TPC4wR1Lyw2YYsUsmJ5/O926cAuclRrP4DGVaFyTWu7dvlXrp9UC rWkAggs99lIDtQwUic825l/5MOVIb6hlsoo+MGQWZsaaKUU00iAbkzb0AD/J2zMhHB2K je/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=zENyOoOSgI8QfaggquPMfPbLKw7a6eUv2Qjm9NWJtcQ=; b=i4v+iDeuIQBQMpszhfhuPpavb8UtffvJ8dGDlrii5++vm0c4h8ep7xXwZLFlNFGjVz HBbB3PRwRoisbIihy7/xw1WhGZWTh/lMC56qL66mOqvY/+IYIyT6Nsj3gtJxc3y723gS FfFtZlma/1trCo/2auTYk8/Zr0ZP/PtxCyS9ZwBhMA5e6HL6zK0etzShIsWEuSWHcj5A s2pOOv9uQruo2kpGD3wtjyWp1x/jbEiMq3TdJqTtF2Fli4rgrYhq5Jda3q7bCP66KdqE ub2sbkM5wEakEjaVgqMi46r3gJl46r3kmwVAOjPOrqLKc+X4topGXyhqif3F+tDnEn0d bW/g== X-Gm-Message-State: APjAAAWXAaw0ge2wsR6GkOPv5MjOtzDl1Jj6E8QmUKZ/f4M7XozP6bxZ xHmd+bkyBoa138R4lNo0I3Q= X-Google-Smtp-Source: APXvYqynFN1ludII3XFLYMfIONiHIRT3DEjMebyu/w5SXt66rSlQbatTCpNAcnVu5y6nlAVVC7h8BQ== X-Received: by 2002:a17:902:b70f:: with SMTP id d15mr3048117pls.318.1560381270418; Wed, 12 Jun 2019 16:14:30 -0700 (PDT) Received: from gmail.com ([2a00:79e1:abc:1e04:de9a:68c:c1e8:7e8f]) by smtp.gmail.com with ESMTPSA id o26sm491338pgv.47.2019.06.12.16.14.29 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 12 Jun 2019 16:14:29 -0700 (PDT) Date: Wed, 12 Jun 2019 16:14:28 -0700 From: Andrei Vagin To: Konstantin Khlebnikov Cc: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Oleg Nesterov , Matthew Wilcox , Michal Hocko , Cyrill Gorcunov , Kirill Tkhai , Michal =?utf-8?Q?Koutn=C3=BD?= , Al Viro , Roman Gushchin , Dmitry Safonov Subject: Re: [PATCH v2 5/6] proc: use down_read_killable mmap_sem for /proc/pid/map_files Message-ID: <20190612231426.GA3639@gmail.com> References: <156007465229.3335.10259979070641486905.stgit@buzz> <156007493995.3335.9595044802115356911.stgit@buzz> MIME-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline In-Reply-To: <156007493995.3335.9595044802115356911.stgit@buzz> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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; >