From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id EDA616B0009 for ; Mon, 26 Feb 2018 19:26:49 -0500 (EST) Received: by mail-pf0-f198.google.com with SMTP id g66so282159pfj.11 for ; Mon, 26 Feb 2018 16:26:49 -0800 (PST) Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com. [115.124.30.133]) by mx.google.com with ESMTPS id y128si6227633pgb.126.2018.02.26.16.26.48 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 26 Feb 2018 16:26:48 -0800 (PST) From: Yang Shi 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> 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: owner-linux-mm@kvack.org List-ID: 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 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org