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=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 9ACC2C468BE for ; Sun, 9 Jun 2019 10:09:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 737A4212F5 for ; Sun, 9 Jun 2019 10:09:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="W2Lns3hn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728256AbfFIKJG (ORCPT ); Sun, 9 Jun 2019 06:09:06 -0400 Received: from forwardcorp1o.mail.yandex.net ([95.108.205.193]:55254 "EHLO forwardcorp1o.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728208AbfFIKJE (ORCPT ); Sun, 9 Jun 2019 06:09:04 -0400 Received: from mxbackcorp2j.mail.yandex.net (mxbackcorp2j.mail.yandex.net [IPv6:2a02:6b8:0:1619::119]) by forwardcorp1o.mail.yandex.net (Yandex) with ESMTP id DB53D2E1290; Sun, 9 Jun 2019 13:09:00 +0300 (MSK) Received: from smtpcorp1j.mail.yandex.net (smtpcorp1j.mail.yandex.net [2a02:6b8:0:1619::137]) by mxbackcorp2j.mail.yandex.net (nwsmtp/Yandex) with ESMTP id HqcI3fm6pO-90dSh3UN; Sun, 09 Jun 2019 13:09:00 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1560074940; bh=HTswKNZVinWlaXTKPwYUewNcuthjMB5ThiabC8k2HqI=; h=In-Reply-To:Message-ID:References:Date:To:From:Subject:Cc; b=W2Lns3hnIOukrTVxWvIo0u6baEU21di7kha/doFaKrXcuN13asxGi1NnamvbmIL6R GG523ZkU7z70oZvqhg6+jHvA2776ywAPGJ7zEEGZCR2c+jbDorSPrGnQHtLbI3fTER zK40ISHd22/ieJqWF7T4KyXDg90PAatMcqztN+vk= Authentication-Results: mxbackcorp2j.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from dynamic-red.dhcp.yndx.net (dynamic-red.dhcp.yndx.net [2a02:6b8:0:40c:3d25:9e27:4f75:a150]) by smtpcorp1j.mail.yandex.net (nwsmtp/Yandex) with ESMTPSA id 1wLN9D4DDw-90emhqeg; Sun, 09 Jun 2019 13:09:00 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) Subject: [PATCH v2 5/6] proc: use down_read_killable mmap_sem for /proc/pid/map_files From: Konstantin Khlebnikov To: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org Cc: Oleg Nesterov , Matthew Wilcox , Michal Hocko , Cyrill Gorcunov , Kirill Tkhai , Michal =?utf-8?q?Koutn=C3=BD?= , Al Viro , Roman Gushchin Date: Sun, 09 Jun 2019 13:09:00 +0300 Message-ID: <156007493995.3335.9595044802115356911.stgit@buzz> In-Reply-To: <156007465229.3335.10259979070641486905.stgit@buzz> References: <156007465229.3335.10259979070641486905.stgit@buzz> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Do not stuck forever if something wrong. Killable lock allows to cleanup stuck tasks and simplifies investigation. 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 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; + 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;