mempolicy: fix get_mempolicy() for relative and static nodes

Discovered while testing other mempolicy changes:

get_mempolicy() does not handle static/relative mode flags correctly.
Return the value that the user specified so that it can be restored
via set_mempolicy() if desired.

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Ravikiran Thirumalai <kiran@scalex86.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 6cdfa1df57f6..8034abd3a135 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -806,9 +806,13 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
 
         err = 0;
         if (nmask) {
-                task_lock(current);
-                get_policy_nodemask(pol, nmask);
-                task_unlock(current);
+                if (mpol_store_user_nodemask(pol)) {
+                        *nmask = pol->w.user_nodemask;
+                } else {
+                        task_lock(current);
+                        get_policy_nodemask(pol, nmask);
+                        task_unlock(current);
+                }
         }
 
  out: