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=-4.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,FSL_HELO_FAKE, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 4CC82C31E46 for ; Wed, 12 Jun 2019 23:14:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 041F3208C2 for ; Wed, 12 Jun 2019 23:14:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="EswV1nGC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 041F3208C2 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 7C7146B000A; Wed, 12 Jun 2019 19:14:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 778976B000D; Wed, 12 Jun 2019 19:14:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6689E6B000E; Wed, 12 Jun 2019 19:14:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) by kanga.kvack.org (Postfix) with ESMTP id 30C636B000A for ; Wed, 12 Jun 2019 19:14:32 -0400 (EDT) Received: by mail-pf1-f198.google.com with SMTP id i123so13055909pfb.19 for ; Wed, 12 Jun 2019 16:14:32 -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:date:from:to:cc:subject :message-id:references:mime-version:content-disposition:in-reply-to :user-agent; bh=zENyOoOSgI8QfaggquPMfPbLKw7a6eUv2Qjm9NWJtcQ=; b=E/sMEI7Qf9GMUjrz0FJvxZiBwyKbB5vRlOum+2ADEi6I0GzWrDfkCNJW14gc118j/b Aa9Nh5i6gWKkiODj1AkBy0rI8ojnWwd2N82cZ8VgI6r2XELDrM/PFmerkFftMgRHxeRt RCXt6tc8nbjlHCC+GkXsSkvvrTLcj3QyakhlYvk7uHRzpDWCwNxJu5iTqegQYur/9z8S idEWtymubjrmJpF9Ti8wWZRPq1m8YSxCh0G6j6EfWw7guGVprf4aCukvZNbt+hfktOt8 XUVj8CxbeIp7Wgb3GfZ6kr9vqL07D5POb8mNxjTtZD23AmkRAIoe+j8gC4JrL3tXQqRF qd9Q== X-Gm-Message-State: APjAAAXrL5KzeEiMzcQ/aR5USwu/EdztO9+FNZ3jiyTjCj0PX3oJfZ+w /lrtgDR+/0OdMbugfGZuL5zF8fyx8mZyF5Z/bw//2RLzLKvZ2A3TgA1G/DolrDgQz0DDbtO69zI 96lVDl8DwKLAqil8zcx63IihFgaE4rR+tu2qztb8Vdhw2Klm+N7fVCQ5p/EemoDsdmA== X-Received: by 2002:a17:90a:de08:: with SMTP id m8mr1622895pjv.50.1560381271661; Wed, 12 Jun 2019 16:14:31 -0700 (PDT) X-Received: by 2002:a17:90a:de08:: with SMTP id m8mr1622846pjv.50.1560381270909; Wed, 12 Jun 2019 16:14:30 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1560381270; cv=none; d=google.com; s=arc-20160816; b=HRVjQdZqHx81moLHudynYqFEXsS2LgLVa5kpXZgF/nqNPeCxYFXv9RnA8j7eD34TPp 9q+uq5MPrEeWQC5A+JZY9dBYnobukCD9OK6KNFZptV9fBO5e3QSJecqQPI5o5OSR79Nw lmu/LLQu07SFUZtLuWQ1dOPRZvsYltETbN3tRBpvqdFt3UP0+r2onwy7AdjTJC2P5ByF 8KAZoF+VuHrcclIWvI0SbuTTOfz1xJk4izaFRm6XVhghtYfpaugQNr5dG9CnMgnv2S1T fYfxpTDKCVlOn9sJmaNrxSOW9vFjkoC7q8UAo5h7wwhYLI2lJ6g9XqeCTj6Pi5HJSS7x uVEg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:dkim-signature; bh=zENyOoOSgI8QfaggquPMfPbLKw7a6eUv2Qjm9NWJtcQ=; b=OsY1jb0rsabhWLfDTExDoYvnHMUy/mut8K+wQ3copMTha8VtQuUD8adxa3OV6ju1M4 lr75Y8c43yIzKki2Yc/t6dXfFfAQn2KLE9LogqPXgWZwE3CpntdqXiw7ahnmr126mW7a 1J4hmPq5o7SMKhdSydZAnVhUnmg9+TmpsrZJLP2AvxiE1/AiB5GBY8rVO1/itdvcKjoL darjWcvFbNdNG1vm5H4lVxqDYKDmvwqN89pBTHSxVCPhTOMUOoObzJl1Sb/WTDRKcTXY PqpGNSDVz8CEGf1AxcWtUlQWGobtIaK1sCGwXT6LQltBg2GA01t2hxXrCG0VkHzpLgu0 ntdg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=EswV1nGC; 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 j39sor1121600plb.22.2019.06.12.16.14.30 for (Google Transport Security); Wed, 12 Jun 2019 16:14:30 -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=EswV1nGC; 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=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-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) 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 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; >