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tmpfs: fix shared mempolicy leak

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This fixes a regression in 3.7-rc, which has since gone into stable.

Commit 00442ad04a ("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 00442ad04a,
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>
This commit is contained in:
Mel Gorman
2012-12-05 14:01:41 -08:00
committed by Linus Torvalds
parent c702418f8a
commit 18a2f371f5
3 changed files with 28 additions and 60 deletions
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16
include/linux/mempolicy.h
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@@ -82,16 +82,6 @@ static inline void mpol_cond_put(struct mempolicy *pol)
__mpol_put(pol);
}
extern struct mempolicy *__mpol_cond_copy(struct mempolicy *tompol,
struct mempolicy *frompol);
static inline struct mempolicy *mpol_cond_copy(struct mempolicy *tompol,
struct mempolicy *frompol)
{
if (!frompol)
return frompol;
return __mpol_cond_copy(tompol, frompol);
}
extern struct mempolicy *__mpol_dup(struct mempolicy *pol);
static inline struct mempolicy *mpol_dup(struct mempolicy *pol)
{
@@ -215,12 +205,6 @@ static inline void mpol_cond_put(struct mempolicy *pol)
{
}
static inline struct mempolicy *mpol_cond_copy(struct mempolicy *to,
struct mempolicy *from)
{
return from;
}
static inline void mpol_get(struct mempolicy *pol)
{
}