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

From: Kirill A. Shutemov
Date: Mon Dec 12 2016 - 16:02:17 EST

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@xxxxxxxxxxxxxxxxxx>

Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

Kirill A. Shutemov