tmpfs: fix shared mempolicy leak
This fixes a regression in 3.7-rc, which has since gone into stable. Commit 00442ad0 ("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 00442ad0, alloc_pages_vma() has kept refcount in balance, so now no problem. Reported-and-tested-by: NTommi Rantala <tt.rantala@gmail.com> Signed-off-by: NMel Gorman <mgorman@suse.de> Signed-off-by: NHugh Dickins <hughd@google.com> Cc: stable@vger.kernel.org Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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