linux-kernel - Re: mm: BUG in do_huge_pmd_wp

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Message-ID: <20140407201106.GA21633@node.dhcp.inet.fi>
Date:	Mon, 7 Apr 2014 23:11:06 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Hugh Dickins <hughd@...gle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Mel Gorman <mgorman@...e.de>,
	Dave Jones <davej@...hat.com>, linux-mm <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: mm: BUG in do_huge_pmd_wp_page

On Mon, Apr 07, 2014 at 03:40:46PM -0400, Sasha Levin wrote:
> It also breaks fairly quickly under testing because:
> 
> On 04/07/2014 10:48 AM, Kirill A. Shutemov wrote:
> > +	if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
> > +		spin_lock(ptl);
> 
> ^ We go into atomic
> 
> > +		if (unlikely(!pmd_same(*pmd, orig_pmd)))
> > +			goto out_race;
> > +	}
> > +
> >  	if (!page)
> >  		clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
> >  	else
> >  		copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
> 
> copy_user_huge_page() doesn't like running in atomic state,
> and asserts might_sleep().

Okay, I'll try something else.

-- 
 Kirill A. Shutemov
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