linux-kernel - Re: [PATCH v3 1/2] mm, proc: Fix region lost in /proc/self/smaps

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Message-ID: <20160923135635.GB28734@redhat.com>
Date:   Fri, 23 Sep 2016 15:56:36 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Robert Ho <robert.hu@...el.com>
Cc:     pbonzini@...hat.com, akpm@...ux-foundation.org, mhocko@...e.com,
        dan.j.williams@...el.com, dave.hansen@...el.com,
        guangrong.xiao@...ux.intel.com, gleb@...nel.org,
        mtosatti@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, stefanha@...hat.com,
        yuhuang@...hat.com, linux-mm@...ck.org,
        ross.zwisler@...ux.intel.com
Subject: Re: [PATCH v3 1/2] mm, proc: Fix region lost in /proc/self/smaps

On 09/23, Robert Ho wrote:
>
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -147,7 +147,7 @@ m_next_vma(struct proc_maps_private *priv, struct vm_area_struct *vma)
>  static void m_cache_vma(struct seq_file *m, struct vm_area_struct *vma)
>  {
>  	if (m->count < m->size)	/* vma is copied successfully */
> -		m->version = m_next_vma(m->private, vma) ? vma->vm_start : -1UL;
> +		m->version = m_next_vma(m->private, vma) ? vma->vm_end : -1UL;
>  }

OK.

>  static void *m_start(struct seq_file *m, loff_t *ppos)
> @@ -176,14 +176,14 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
>  
>  	if (last_addr) {
>  		vma = find_vma(mm, last_addr);
> -		if (vma && (vma = m_next_vma(priv, vma)))
> +		if (vma)
>  			return vma;
>  	}

I think we can simplify this patch. And imo make it better. How about

	if (last_addr) {
		vma = find_vma(mm, last_addr - 1);
		if (vma && vma->vm_start <= last_addr)
			vma = m_next_vma(priv, vma);
		if (vma)
			return vma;
	}

?

This way we do not need other changes in show_map_vma(), and the same vma
won't be reported twice (as 2 different vma's) if it grows in between.

Oleg.