Commit ae4d8c16 authored Apr 28, 2008 by Lee Schermerhorn Committed by Linus Torvalds Apr 28, 2008

mempolicy: fixup Fallback for Default Shmem Policy



get_vma_policy() is not handling fallback to task policy correctly when the
get_policy() vm_op returns NULL.  The NULL overwrites the 'pol' variable that
was holding the fallback task mempolicy.  So, it was falling back directly to
system default policy.

Fix get_vma_policy() to use only non-NULL policy returned from the vma
get_policy op.

shm_get_policy() was falling back to current task's mempolicy if the "backing
file system" [tmpfs vs hugetlbfs] does not support the get_policy vm_op and
the vma policy is null.  This is incorrect for show_numa_maps() which is
likely querying the numa_maps of some task other than current.  Remove this
fallback.

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f4e53d91

ipc/shm.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -274,8 +274,7 @@ static struct mempolicy shm_get_policy(struct vm_area_struct vma,
		else if (vma->vm_policy) {
		pol = vma->vm_policy;
		mpol_get(pol); /* get_vma_policy() expects this */
		} else
		pol = current->mempolicy;
		}
		return pol;
		}
		#endif

mm/mempolicy.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -1270,7 +1270,10 @@ static struct mempolicy * get_vma_policy(struct task_struct *task,

		if (vma) {
		if (vma->vm_ops && vma->vm_ops->get_policy) {
		pol = vma->vm_ops->get_policy(vma, addr);
		struct mempolicy *vpol = vma->vm_ops->get_policy(vma,
		addr);
		if (vpol)
		pol = vpol;
		shared_pol = 1; /* if pol non-NULL, add ref below */
		} else if (vma->vm_policy &&
		vma->vm_policy->policy != MPOL_DEFAULT)