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Date: Wed, 22 Jan 2014 20:43:27 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Alex Thorlton <athorlton@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Rik van Riel <riel@redhat.com>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Al Viro <viro@zeniv.linux.org.uk>, Kees Cook <keescook@chromium.org>,
        Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH 0/2] mm->def_flags cleanups (Was: Change khugepaged to
	respect MMF_THP_DISABLE flag)
Message-ID: <20140122194327.GA2826@redhat.com>
References: <1bc8f911363af956b37d8ea415d734f3191f1c78.1389905087.git.athorlton@sgi.com> <13c9d1b0213af7cee7afb54de368a0b189e98df8.1389905087.git.athorlton@sgi.com> <20140118234957.GB10970@node.dhcp.inet.fi> <20140120195812.GD18196@sgi.com> <20140120201525.GA31416@redhat.com> <20140120204108.GE18196@sgi.com> <20140122174553.GA29710@redhat.com> <20140122184042.GQ18196@sgi.com> <20140122192514.GA1779@redhat.com>
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On 01/22, Oleg Nesterov wrote:
>
> On 01/22, Alex Thorlton wrote:
> > > +	case PR_SET_THP_DISABLE:
> > > +	case PR_GET_THP_DISABLE:
> > > +		down_write(&me->mm->mmap_sem);
> > > +		if (option == PR_SET_THP_DISABLE) {
> > > +			if (arg2)
> > > +				me->mm->def_flags |= VM_NOHUGEPAGE;
> > > +			else
> > > +				me->mm->def_flags &= ~VM_NOHUGEPAGE;
> > > +		} else {
> > > +			error = !!(me->mm->flags && VM_NOHUGEPAGE);
> >
> > Should be:
> >
> > error = !!(me->mm->def_flags && VM_NOHUGEPAGE);
>
> No, we need to return 1 if this bit is set ;)

Damn, you are right of course, we need "&". I didn't notice "&&"
in the patch I sent and misunderstood your "&&" above ;) Sorry.

Oleg.

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