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	Original line	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) {		else if (vma->vm_policy) {
	pol = vma->vm_policy;		pol = vma->vm_policy;
	mpol_get(pol); /* get_vma_policy() expects this */		mpol_get(pol); /* get_vma_policy() expects this */
	} else		}
	pol = current->mempolicy;
	return pol;		return pol;
	}		}
	#endif		#endif

mm/mempolicy.c

+5 −2

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

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

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