linux-kernel - Re: [PATCH 2/2] mm/thp/pagecache/collapse: Free the pte page table on collapse for thp page cache.

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Date:   Tue, 13 Dec 2016 00:02:09 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:     akpm@...ux-foundation.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        mpe@...erman.id.au, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm/thp/pagecache/collapse: Free the pte page table
 on collapse for thp page cache.

On Mon, Dec 12, 2016 at 10:04:28PM +0530, Aneesh Kumar K.V wrote:
> With THP page cache, when trying to build a huge page from regular pte pages,
> we just clear the pmd entry. We will take another fault and at that point we
> will find the huge page in the radix tree, thereby using the huge page to
> complete the page fault
> 
> The second fault path will allocate the needed pgtable_t page for archs like
> ppc64. So no need to deposit the same in collapse path. Depositing them in
> the collapse path resulting in a pgtable_t memory leak also giving errors like
> "[ 2362.021762] BUG: non-zero nr_ptes on freeing mm: 3"
> 
> Fixes:"mm: THP page cache support for ppc64"
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
 Kirill A. Shutemov