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Date: Fri, 14 Dec 2012 14:25:52 -0800
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
alan@...rguk.ukuu.org.uk, Mel Gorman <mgorman@...e.de>,
Hugh Dickins <hughd@...gle.com>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [ 07/22] tmpfs: fix shared mempolicy leak
3.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mel Gorman <mgorman@...e.de>
commit 18a2f371f5edf41810f6469cb9be39931ef9deb9 upstream.
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@...il.com>
Signed-off-by: Mel Gorman <mgorman@...e.de>
Signed-off-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
include/linux/mempolicy.h | 16 ----------------
mm/mempolicy.c | 22 ----------------------
mm/shmem.c | 22 +++++++++++++---------
3 files changed, 13 insertions(+), 47 deletions(-)
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -137,16 +137,6 @@ static inline void mpol_cond_put(struct
__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)
{
@@ -270,12 +260,6 @@ static inline void mpol_cond_put(struct
{
}
-static inline struct mempolicy *mpol_cond_copy(struct mempolicy *to,
- struct mempolicy *from)
-{
- return from;
-}
-
static inline void mpol_get(struct mempolicy *pol)
{
}
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1973,28 +1973,6 @@ struct mempolicy *__mpol_dup(struct memp
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 */
int __mpol_equal(struct mempolicy *a, struct mempolicy *b)
{
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1168,19 +1168,20 @@ static struct mempolicy *shmem_get_sbmpo
static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
struct shmem_inode_info *info, unsigned long idx)
{
- struct mempolicy mpol, *spol;
struct vm_area_struct pvma;
struct page *page;
- spol = mpol_cond_copy(&mpol,
- mpol_shared_policy_lookup(&info->policy, idx));
-
/* Create a pseudo vma that just contains the policy */
pvma.vm_start = 0;
pvma.vm_pgoff = idx;
pvma.vm_ops = NULL;
- pvma.vm_policy = spol;
+ pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
+
page = swapin_readahead(entry, gfp, &pvma, 0);
+
+ /* Drop reference taken by mpol_shared_policy_lookup() */
+ mpol_cond_put(pvma.vm_policy);
+
return page;
}
@@ -1188,6 +1189,7 @@ static struct page *shmem_alloc_page(gfp
struct shmem_inode_info *info, unsigned long idx)
{
struct vm_area_struct pvma;
+ struct page *page;
/* Create a pseudo vma that just contains the policy */
pvma.vm_start = 0;
@@ -1195,10 +1197,12 @@ static struct page *shmem_alloc_page(gfp
pvma.vm_ops = NULL;
pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
- /*
- * alloc_page_vma() will drop the shared policy reference
- */
- return alloc_page_vma(gfp, &pvma, 0);
+ page = alloc_page_vma(gfp, &pvma, 0);
+
+ /* Drop reference taken by mpol_shared_policy_lookup() */
+ mpol_cond_put(pvma.vm_policy);
+
+ return page;
}
#else /* !CONFIG_NUMA */
#ifdef CONFIG_TMPFS
--
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