[PATCH] tmpfs: fix shared mempolicy leak
From: Mel Gorman
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
Signed-off-by: Mel Gorman
Signed-off-by: Hugh Dickins
Cc: sta...@vger.kernel.org
---
include/linux/mempolicy.h | 16
mm/mempolicy.c| 22 --
mm/shmem.c| 26 --
3 files changed, 16 insertions(+), 48 deletions(-)
--- 3.7-rc8/include/linux/mempolicy.h 2012-10-14 16:16:57.637308925 -0700
+++ linux/include/linux/mempolicy.h 2012-12-04 22:38:21.812178829 -0800
@@ -82,16 +82,6 @@ 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)
{
@@ -215,12 +205,6 @@ 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)
{
}
--- 3078/mm/mempolicy.c 2012-10-20 20:56:24.675917367 -0700
+++ 3078X/mm/mempolicy.c2012-12-04 22:33:31.516171929 -0800
@@ -2037,28 +2037,6 @@ 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 */
bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
{
--- 3078/mm/shmem.c 2012-11-16 19:26:56.388459961 -0800
+++ 3078X/mm/shmem.c2012-12-04 22:32:35.328170594 -0800
@@ -910,25 +910,29 @@ static struct mempolicy *shmem_get_sbmpo
static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
- struct mempolicy mpol, *spol;
struct vm_area_struct pvma;
-
- spol = mpol_cond_copy(&mpol,
- mpol_shared_policy_lookup(&info->policy, index));
+ struct page *page;
/* Create a pseudo vma that just contains the policy */
pvma.vm_start = 0;
/* Bias interleave by inode number to distribute better across nodes */
pvma.vm_pgoff = index + info->vfs_inode.i_ino;
pvma.vm_ops = NULL;
- pvma.vm_policy = spol;
- return swapin_readahead(swap, gfp, &pvma, 0);
+ pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
+
+ page = swapin_readahead(swap, gfp, &pvma, 0);
+
+ /* Drop reference taken by mpol_shared_policy_lookup() */
+ mpol_cond_put(pvma.vm_policy);
+
+ return page;
}
static struct page *shmem_alloc_page(gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
struct vm_area_struct pvma;
+ struct page *page;
/* Create a pseudo vma that just contains the policy */
pvma.vm_start = 0;
@@ -937,10 +941,12 @@ static struct page *shmem_alloc_page(gfp
pvma.vm_ops = NULL;
pvma.vm_policy = mpol_shared_policy_lookup(&i
Re: [PATCH] tmpfs: fix shared mempolicy leak
On Wed, 5 Dec 2012, Tommi Rantala wrote:
> 2012/12/5 Mel Gorman :
> > On Tue, Dec 04, 2012 at 11:24:30PM -0800, Hugh Dickins wrote:
> >> From: Mel Gorman
> >>
> >> 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().
> >
> > Thanks Hugh for turning gibber into a patch!
> >
> > Signed-off-by: Mel Gorman
> >
> > Tommi, just in case, can you confirm this fixes the problem for you please?
>
> Confirmed! No more complaints from kmemleak.
Great, thanks. I'll update the tags and send straight to Linus now.
Hugh
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Re: [PATCH] tmpfs: fix shared mempolicy leak
2012/12/5 Mel Gorman :
> On Tue, Dec 04, 2012 at 11:24:30PM -0800, Hugh Dickins wrote:
>> From: Mel Gorman
>>
>> 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().
>
> Thanks Hugh for turning gibber into a patch!
>
> Signed-off-by: Mel Gorman
>
> Tommi, just in case, can you confirm this fixes the problem for you please?
Confirmed! No more complaints from kmemleak.
Thanks,
Tommi
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Re: [PATCH] tmpfs: fix shared mempolicy leak
On Tue, Dec 04, 2012 at 11:24:30PM -0800, Hugh Dickins wrote:
> From: Mel Gorman
>
> 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
> Awaiting-signed-off-by: Mel Gorman
> Signed-off-by: Hugh Dickins
> Cc: sta...@vger.kernel.org
Thanks Hugh for turning gibber into a patch!
Signed-off-by: Mel Gorman
Tommi, just in case, can you confirm this fixes the problem for you please?
--
Mel Gorman
SUSE Labs
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Please read the FAQ at http://www.tux.org/lkml/
[PATCH] tmpfs: fix shared mempolicy leak
From: Mel Gorman
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-by: Tommi Rantala
Awaiting-signed-off-by: Mel Gorman
Signed-off-by: Hugh Dickins
Cc: sta...@vger.kernel.org
---
include/linux/mempolicy.h | 16
mm/mempolicy.c| 22 --
mm/shmem.c| 26 --
3 files changed, 16 insertions(+), 48 deletions(-)
--- 3.7-rc8/include/linux/mempolicy.h 2012-10-14 16:16:57.637308925 -0700
+++ linux/include/linux/mempolicy.h 2012-12-04 22:38:21.812178829 -0800
@@ -82,16 +82,6 @@ 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)
{
@@ -215,12 +205,6 @@ 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)
{
}
--- 3078/mm/mempolicy.c 2012-10-20 20:56:24.675917367 -0700
+++ 3078X/mm/mempolicy.c2012-12-04 22:33:31.516171929 -0800
@@ -2037,28 +2037,6 @@ 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 */
bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
{
--- 3078/mm/shmem.c 2012-11-16 19:26:56.388459961 -0800
+++ 3078X/mm/shmem.c2012-12-04 22:32:35.328170594 -0800
@@ -910,25 +910,29 @@ static struct mempolicy *shmem_get_sbmpo
static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
- struct mempolicy mpol, *spol;
struct vm_area_struct pvma;
-
- spol = mpol_cond_copy(&mpol,
- mpol_shared_policy_lookup(&info->policy, index));
+ struct page *page;
/* Create a pseudo vma that just contains the policy */
pvma.vm_start = 0;
/* Bias interleave by inode number to distribute better across nodes */
pvma.vm_pgoff = index + info->vfs_inode.i_ino;
pvma.vm_ops = NULL;
- pvma.vm_policy = spol;
- return swapin_readahead(swap, gfp, &pvma, 0);
+ pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
+
+ page = swapin_readahead(swap, gfp, &pvma, 0);
+
+ /* Drop reference taken by mpol_shared_policy_lookup() */
+ mpol_cond_put(pvma.vm_policy);
+
+ return page;
}
static struct page *shmem_alloc_page(gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
struct vm_area_struct pvma;
+ struct page *page;
/* Create a pseudo vma that just contains the policy */
pvma.vm_start = 0;
@@ -937,10 +941,12 @@ static struct page *shmem_alloc_page(gfp
pvma.vm_ops = NULL;
pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
- /*
-* alloc_page_vma() will drop
