linux-kernel - Re: [PATCH v2 1/1] userfaultfd: don't pin the user memory in userfaultfd_file

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Message-ID: <20160517163044.GA31867@redhat.com>
Date:	Tue, 17 May 2016 18:30:44 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 1/1] userfaultfd: don't pin the user memory in
 userfaultfd_file_create()

On 05/17, Michal Hocko wrote:
>
> On Mon 16-05-16 19:22:54, Oleg Nesterov wrote:
>
> > The patch adds the new trivial helper, mmget_not_zero(), it can have more users.
>
> Is this really helpful?

Well, this is subjective of course, but I think the code looks a bit better this
way. uprobes, fs/proc and more can use this helper too.

And in fact the initial version of this patch did atomic_inc_not_zero(mm->users) by
hand, then it was suggested to add a helper.

> > Signed-off-by: Oleg Nesterov <oleg@...hat.com>
>
> The patch seems good to me but I am not familiar with the userfaultfd
> internals enought to give you reviewed-by nor acked-by. I welcome the
> change anyway.

Thanks ;)

Oleg.