linux-kernel - Re: [PATCH v2 1/7] fs/proc/task_mmu.c: don't use task->mm in m_start() and show

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Date:	Wed, 6 Aug 2014 21:41:29 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	David Howells <dhowells@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Sasha Levin <levinsasha928@...il.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/7] fs/proc/task_mmu.c: don't use task->mm in
	m_start() and show_*map()

On 08/06, Oleg Nesterov wrote:
>
> On 08/06, Kirill A. Shutemov wrote:
> >
> > On Tue, Aug 05, 2014 at 09:46:44PM +0200, Oleg Nesterov wrote:
> > >
> > >  	if (m->count < m->size)  /* vma is copied successfully */
> > > -		m->version = (vma != get_gate_vma(task->mm))
> > > +		m->version = (vma != priv->tail_vma)
> > >  			? vma->vm_start : 0;
> >
> > Drop excessive parenthesis while you're there? And in the next hunk.
>
> I agree. But lets do this in another patch? I forgot to mention this in
> the yesterday's TODO, but we should factor out this code. Perhaps move
> this into vma_stop(). Or at least add a trivial helper, this pattern
> repeats 3 times, plus another one in m_start(). This problem is that I
> do not really understand this logic right now, but I'll do something
> today in any case.

Damn, this needs even more cleanups than I thought. Even "version == -1"
logic is absolutely wrong/dead. And "last_addr rather than next_addr" is
wrong too afaics, this just means we need the extra ->vm_next step plus
vma-or-tail_vma recheck.

Hopefully I'll finish this tomorrow.

Oleg.

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