linux-kernel - Re: [PATCH v4 06/11] mm: thp: check pmd migration entry in common path

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Message-ID: <20170324165014.2ibdmurirjd4pa7r@node.shutemov.name>
Date:   Fri, 24 Mar 2017 19:50:14 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Zi Yan <zi.yan@...rutgers.edu>
Cc:     Zi Yan <zi.yan@...t.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, kirill.shutemov@...ux.intel.com,
        akpm@...ux-foundation.org, minchan@...nel.org, vbabka@...e.cz,
        mgorman@...hsingularity.net, mhocko@...nel.org,
        n-horiguchi@...jp.nec.com, khandual@...ux.vnet.ibm.com,
        dnellans@...dia.com
Subject: Re: [PATCH v4 06/11] mm: thp: check pmd migration entry in common
 path

On Fri, Mar 24, 2017 at 11:09:25AM -0500, Zi Yan wrote:
> Kirill A. Shutemov wrote:
> > On Mon, Mar 13, 2017 at 11:45:02AM -0400, Zi Yan wrote:
> > Again. That's doesn't look right..
> 
> It will be changed:
> 
>  	ptl = pmd_lock(mm, pmd);
> +retry_locked:
> +	if (unlikely(!pmd_present(*pmd))) {
> +		if (likely(!(flags & FOLL_MIGRATION))) {
> +			spin_unlock(ptl);
> +			return no_page_table(vma, flags);
> +		}
> +		pmd_migration_entry_wait(mm, pmd);
> +		goto retry_locked;

Nope. pmd_migration_entry_wait() unlocks the ptl.

-- 
 Kirill A. Shutemov