linux-kernel - Re: [PATCH 4/5] proc: use down_read_killable for /proc/pid/clear

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Date:   Fri, 17 May 2019 14:47:59 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Cyrill Gorcunov <gorcunov@...il.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 4/5] proc: use down_read_killable for /proc/pid/clear_refs

On Wed 15-05-19 11:41:21, Konstantin Khlebnikov wrote:
> Replace the only unkillable mmap_sem lock in clear_refs_write.

Poor changelog again.

The change itself looks ok to me.

> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> ---
>  fs/proc/task_mmu.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 78bed6adc62d..7f84d1477b5b 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -1140,7 +1140,10 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
>  			goto out_mm;
>  		}
>  
> -		down_read(&mm->mmap_sem);
> +		if (down_read_killable(&mm->mmap_sem)) {
> +			count = -EINTR;
> +			goto out_mm;
> +		}
>  		tlb_gather_mmu(&tlb, mm, 0, -1);
>  		if (type == CLEAR_REFS_SOFT_DIRTY) {
>  			for (vma = mm->mmap; vma; vma = vma->vm_next) {

-- 
Michal Hocko
SUSE Labs