cpusets: randomize node rotor used in cpuset_mem_spread_node()

[ This patch has already been accepted as commit 0ac0c0d0f837 but later
  reverted (commit 35926ff5fba8) because it itroduced arch specific
  __node_random which was defined only for x86 code so it broke other
  archs.  This is a followup without any arch specific code.  Other than
  that there are no functional changes.]

Some workloads that create a large number of small files tend to assign
too many pages to node 0 (multi-node systems).  Part of the reason is
that the rotor (in cpuset_mem_spread_node()) used to assign nodes starts
at node 0 for newly created tasks.

This patch changes the rotor to be initialized to a random node number
of the cpuset.

[[email protected]: fix layout]
[[email protected]: Define stub numa_random() for !NUMA configuration]
[[email protected]: Make it arch independent]
[[email protected]: fix CONFIG_NUMA=y, MAX_NUMNODES>1 build]
Signed-off-by: Jack Steiner <[email protected]>
Signed-off-by: Lee Schermerhorn <[email protected]>
Signed-off-by: Michal Hocko <[email protected]>
Reviewed-by: KOSAKI Motohiro <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Paul Menage <[email protected]>
Cc: Jack Steiner <[email protected]>
Cc: Robin Holt <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Jack Steiner <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Lee Schermerhorn <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Paul Menage <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Robin Holt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 3f3b68199d74..37ef4b048795 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -756,7 +756,7 @@ static int bitmap_pos_to_ord(const unsigned long *buf, int pos, int bits)
  *
  * The bit positions 0 through @bits are valid positions in @buf.
  */
-static int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)
+int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)
 {
 	int pos = 0;