path: root/mm/mempolicy.c
diff options
authorMel Gorman <mgorman@suse.de>2012-12-05 14:01:41 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-06 11:56:43 -0800
commit18a2f371f5edf41810f6469cb9be39931ef9deb9 (patch)
tree4e4ec26f13273b36fc7203d2084ea09f14c5f0f7 /mm/mempolicy.c
parentc702418f8a2fa6cc92e84a39880d458faf7af9cc (diff)
tmpfs: fix shared mempolicy leak
This fixes a regression in 3.7-rc, which has since gone into stable. 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. Reported-and-tested-by: Tommi Rantala <tt.rantala@gmail.com> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Hugh Dickins <hughd@google.com> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mempolicy.c')
1 files changed, 0 insertions, 22 deletions
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d04a8a54c29..4ea600da894 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2037,28 +2037,6 @@ struct mempolicy *__mpol_dup(struct mempolicy *old)
return new;
- * If *frompol needs [has] an extra ref, copy *frompol to *tompol ,
- * eliminate the * MPOL_F_* flags that require conditional ref and
- * [NOTE!!!] drop the extra ref. Not safe to reference *frompol directly
- * after return. Use the returned value.
- *
- * Allows use of a mempolicy for, e.g., multiple allocations with a single
- * policy lookup, even if the policy needs/has extra ref on lookup.
- * shmem_readahead needs this.
- */
-struct mempolicy *__mpol_cond_copy(struct mempolicy *tompol,
- struct mempolicy *frompol)
- if (!mpol_needs_cond_ref(frompol))
- return frompol;
- *tompol = *frompol;
- tompol->flags &= ~MPOL_F_SHARED; /* copy doesn't need unref */
- __mpol_put(frompol);
- return tompol;
/* Slow path of a mempolicy comparison */
bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)