On Tue, Dec 04, 2012 at 11:24:30PM -0800, Hugh Dickins wrote:
> From: Mel Gorman <mgor...@suse.de>
>
> Commit 00442ad04a5e ("mempolicy: fix a memory corruption by refcount
> imbalance in alloc_pages_vma()") changed get_vma_policy() to raise the
> refcount on a shmem shared mempolicy; whereas shmem_alloc_page() went
> on expecting alloc_page_vma() to drop the refcount it had acquired.
> This deserves a rework: but for now fix the leak in shmem_alloc_page().
>
> Hugh: shmem_swapin() did not need a fix, but surely it's clearer to use
> the same refcounting there as in shmem_alloc_page(), delete its onstack
> mempolicy, and the strange mpol_cond_copy() and __mpol_cond_copy() -
> those were invented to let swapin_readahead() make an unknown number of
> calls to alloc_pages_vma() with one mempolicy; but since 00442ad04a5e,
> alloc_pages_vma() has kept refcount in balance, so now no problem.
>
Agreed. Anything that reduces the complexity of the mempolicy ref counting
is worthwhile even if it's only by a small bit.
> Reported-by: Tommi Rantala <tt.rant...@gmail.com>
> Awaiting-signed-off-by: Mel Gorman <mgor...@suse.de>
> Signed-off-by: Hugh Dickins <hu...@google.com>
> Cc: sta...@vger.kernel.org
Thanks Hugh for turning gibber into a patch!
Signed-off-by: Mel Gorman <mgor...@suse.de>
Tommi, just in case, can you confirm this fixes the problem for you please?
--
Mel Gorman
SUSE Labs
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