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>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index c6c61ea..8924aaf 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1262,7 +1262,7 @@
* @task != current]. It is the caller's responsibility to
* free the reference in these cases.
*/
-static struct mempolicy * get_vma_policy(struct task_struct *task,
+static struct mempolicy *get_vma_policy(struct task_struct *task,
struct vm_area_struct *vma, unsigned long addr)
{
struct mempolicy *pol = task->mempolicy;
@@ -1270,7 +1270,10 @@
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)