linux-kernel - Re: [PATCH 2/5] proc: use down_read_killable for /proc/pid/smaps

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Date:   Fri, 17 May 2019 14:45:55 +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 2/5] proc: use down_read_killable for
 /proc/pid/smaps_rollup

On Wed 15-05-19 11:41:14, Konstantin Khlebnikov wrote:
> Ditto.

Proper changelog or simply squash those patches into a single patch if
you do not feel like copy&paste is fun

> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> ---
>  fs/proc/task_mmu.c |    8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 2bf210229daf..781879a91e3b 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -832,7 +832,10 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
>  
>  	memset(&mss, 0, sizeof(mss));
>  
> -	down_read(&mm->mmap_sem);
> +	ret = down_read_killable(&mm->mmap_sem);
> +	if (ret)
> +		goto out_put_mm;

Why not ret = -EINTR. The seq_file code seems to be handling all errors
AFAICS.

> +
>  	hold_task_mempolicy(priv);
>  
>  	for (vma = priv->mm->mmap; vma; vma = vma->vm_next) {
> @@ -849,8 +852,9 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
>  
>  	release_task_mempolicy(priv);
>  	up_read(&mm->mmap_sem);
> -	mmput(mm);
>  
> +out_put_mm:
> +	mmput(mm);
>  out_put_task:
>  	put_task_struct(priv->task);
>  	priv->task = NULL;

-- 
Michal Hocko
SUSE Labs