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Subject: Re: [PATCH 3/9] mm: postpone page table allocation until do_set_pte()
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Hugh Dickins <hughd@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>
References: <1447889136-6928-1-git-send-email-kirill.shutemov@linux.intel.com>
 <1447889136-6928-4-git-send-email-kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>, Christoph Lameter <cl@gentwo.org>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Jerome Marchand <jmarchan@redhat.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
From: Dave Hansen <dave.hansen@intel.com>
Message-ID: <565E08C5.8090607@intel.com>
Date: Tue, 1 Dec 2015 12:53:25 -0800
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On 11/18/2015 03:25 PM, Kirill A. Shutemov wrote:
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2068,11 +2068,6 @@ void filemap_map_pages(struct fault_env *fe,
...
>  		if (file->f_ra.mmap_miss > 0)
>  			file->f_ra.mmap_miss--;
> -		do_set_pte(fe, page);
> +
> +		fe->address += (iter.index - last_pgoff) << PAGE_SHIFT;
> +		if (fe->pte)
> +			fe->pte += iter.index - last_pgoff;
> +		last_pgoff = iter.index;
> +		if (do_set_pte(fe, NULL, page)) {
> +			/* failed to setup page table: giving up */
> +			if (!fe->pte)
> +				break;
> +			goto unlock;
> +		}
>  		unlock_page(page);
>  		goto next;

Hey Kirill,

Is there a case here where do_set_pte() returns an error and _still_
manages to populate fe->pte?