[patch 13/26] hugetlb: fix get_policy for stacked shared memory files

[Greg KH <gregkh@suse.de>]

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-stable review patch.  If anyone has any objections, please let us know.

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From: Adam Litke <agl@us.ibm.com>

Here's another breakage as a result of shared memory stacked files :(

The NUMA policy for a VMA is determined by checking the following (in the
order given):

1) vma->vm_ops->get_policy() (if defined)
2) vma->vm_policy (if defined)
3) task->mempolicy (if defined)
4) Fall back to default_policy

By switching to stacked files for shared memory, get_policy() is now always
set to shm_get_policy which is a wrapper function.  This causes us to stop
at step 1, which yields NULL for hugetlb instead of task->mempolicy which
was the previous (and correct) result.

This patch modifies the shm_get_policy() wrapper to maintain steps 1-3 for
the wrapped vm_ops.

(akpm: the refcounting of mempolicies is busted and this patch does nothing to
improve it)

Signed-off-by: Adam Litke <agl@us.ibm.com>
Acked-by: William Irwin <bill.irwin@oracle.com>
Cc: dean gaudet <dean@arctic.org>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

 ipc/shm.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- linux-2.6.21.6.orig/ipc/shm.c
+++ linux-2.6.21.6/ipc/shm.c
@@ -254,8 +254,10 @@ struct mempolicy *shm_get_policy(struct 
 
 	if (sfd->vm_ops->get_policy)
 		pol = sfd->vm_ops->get_policy(vma, addr);
-	else
+	else if (vma->vm_policy)
 		pol = vma->vm_policy;
+	else
+		pol = current->mempolicy;
 	return pol;
 }
 #endif

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