From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751779AbeB0A1B (ORCPT ); Mon, 26 Feb 2018 19:27:01 -0500 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:50004 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751744AbeB0A1A (ORCPT ); Mon, 26 Feb 2018 19:27:00 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07417;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0SyYb1iR_1519691153; From: Yang Shi To: akpm@linux-foundation.org, mingo@kernel.org, adobriyan@gmail.com Cc: yang.shi@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 3/4 v2] fs: proc: use down_read_killable() in environ_read() Date: Tue, 27 Feb 2018 08:25:50 +0800 Message-Id: <1519691151-101999-4-git-send-email-yang.shi@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1519691151-101999-1-git-send-email-yang.shi@linux.alibaba.com> References: <1519691151-101999-1-git-send-email-yang.shi@linux.alibaba.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Like reading /proc/*/cmdline, it is possible to be blocked for long time when reading /proc/*/environ when manipulating large mapping at the mean time. The environ reading process will be waiting for mmap_sem become available for a long time then it may cause the reading task hung. Convert down_read() and access_remote_vm() to killable version. Signed-off-by: Yang Shi Suggested-by: Alexey Dobriyan --- fs/proc/base.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 9bdb84b..d87d9ab 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -933,7 +933,9 @@ static ssize_t environ_read(struct file *file, char __user *buf, if (!mmget_not_zero(mm)) goto free; - down_read(&mm->mmap_sem); + ret = down_read_killable(&mm->mmap_sem); + if (ret) + goto out_mmput; env_start = mm->env_start; env_end = mm->env_end; up_read(&mm->mmap_sem); @@ -950,7 +952,8 @@ static ssize_t environ_read(struct file *file, char __user *buf, max_len = min_t(size_t, PAGE_SIZE, count); this_len = min(max_len, this_len); - retval = access_remote_vm(mm, (env_start + src), page, this_len, 0); + retval = access_remote_vm_killable(mm, (env_start + src), + page, this_len, 0); if (retval <= 0) { ret = retval; @@ -968,6 +971,8 @@ static ssize_t environ_read(struct file *file, char __user *buf, count -= retval; } *ppos = src; + +out_mmput: mmput(mm); free: -- 1.8.3.1