linux-kernel - Re: [RFC PATCHv2 1/2] Add mm flag to control THP

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Message-ID: <20140117200923.GA15234@redhat.com>
Date:	Fri, 17 Jan 2014 21:09:23 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Alex Thorlton <athorlton@....com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Rik van Riel <riel@...hat.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andy Lutomirski <luto@...capital.net>,
	Al Viro <viro@...iv.linux.org.uk>,
	Kees Cook <keescook@...omium.org>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [RFC PATCHv2 1/2] Add mm flag to control THP

On 01/16, Alex Thorlton wrote:
>
> +	case PR_GET_THP_DISABLE:
> +		error = put_user(test_bit(MMF_THP_DISABLE,
> +				 &me->mm->flags),
> +				 (int __user *) arg2);
> +		break;

Do we really want put_user?

	error = test_bit(MMF_THP_DISABLE);

can work too and looks simpler (and to me simpler to use in userspace).

PR_GET_DUMPABLE works this way.

Oleg.

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