From: Alexey Dobriyan <adobriyan@gmail.com>
To: Yang Shi <yang.shi@linux.alibaba.com>
Cc: akpm@linux-foundation.org, mingo@kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/4 v2] fs: proc: use down_read_killable() in environ_read()
Date: Tue, 27 Feb 2018 10:15:36 +0300 [thread overview]
Message-ID: <20180227071536.GA5234@avx2> (raw)
In-Reply-To: <1519691151-101999-4-git-send-email-yang.shi@linux.alibaba.com>
On Tue, Feb 27, 2018 at 08:25:50AM +0800, Yang Shi wrote:
> 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 <yang.shi@linux.alibaba.com>
> Suggested-by: Alexey Dobriyan <adobriyan@gmail.com>
Ehh, bloody tags.
I didn't suggest _killable() variants, they're quite ugly because API
multiplies. access_remote_vm() could be converted to down_read_killable().
> --- 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);
next prev parent reply other threads:[~2018-02-27 7:15 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-27 0:25 [RFC PATCH 0/4 v2] Define killable version for access_remote_vm() and use it in fs/proc Yang Shi
2018-02-27 0:25 ` [PATCH 1/4 v2] mm: add access_remote_vm_killable APIs Yang Shi
2018-02-27 0:25 ` [PATCH 2/4 v2] fs: proc: use down_read_killable in proc_pid_cmdline_read() Yang Shi
2018-02-27 0:25 ` [PATCH 3/4 v2] fs: proc: use down_read_killable() in environ_read() Yang Shi
2018-02-27 7:15 ` Alexey Dobriyan [this message]
2018-02-27 16:59 ` Yang Shi
2018-02-27 0:25 ` [PATCH 4/4 v2] mm: use access_remote_vm() in get_cmdline() Yang Shi
2018-02-27 1:02 ` [RFC PATCH 0/4 v2] Define killable version for access_remote_vm() and use it in fs/proc David Rientjes
2018-02-27 1:25 ` Yang Shi
2018-02-27 1:47 ` David Rientjes
2018-03-01 0:17 ` Yang Shi
2018-03-06 18:45 ` Yang Shi
2018-03-06 20:45 ` Andrew Morton
2018-03-06 21:17 ` Yang Shi
2018-03-06 21:41 ` Andrew Morton
2018-03-07 0:47 ` Yang Shi
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