mempolicy: disallow static or relative flags for local preferred mode
MPOL_F_STATIC_NODES and MPOL_F_RELATIVE_NODES don't mean anything for
MPOL_PREFERRED policies that were created with an empty nodemask (for purely
local allocations). They'll never be invalidated because the allowed mems of
a task changes or need to be rebound relative to a cpuset's placement.
Also fixes a bug identified by Lee Schermerhorn that disallowed empty
nodemasks to be passed to MPOL_PREFERRED to specify local allocations. [A
different, somewhat incomplete, patch already existed in 25-rc5-mm1.]
Cc: Paul Jackson <pj@sgi.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/vm/numa_memory_policy.txt b/Documentation/vm/numa_memory_policy.txt
index 706410d..1c7dd21 100644
--- a/Documentation/vm/numa_memory_policy.txt
+++ b/Documentation/vm/numa_memory_policy.txt
@@ -205,6 +205,12 @@
local allocation for a specific range of addresses--i.e. for
VMA policies.
+ It is possible for the user to specify that local allocation is
+ always preferred by passing an empty nodemask with this mode.
+ If an empty nodemask is passed, the policy cannot use the
+ MPOL_F_STATIC_NODES or MPOL_F_RELATIVE_NODES flags described
+ below.
+
MPOL_INTERLEAVED: This mode specifies that page allocations be
interleaved, on a page granularity, across the nodes specified in
the policy. This mode also behaves slightly differently, based on
@@ -254,7 +260,10 @@
occurs over that node. If no nodes from the user's nodemask are
now allowed, the Default behavior is used.
- MPOL_F_STATIC_NODES cannot be used with MPOL_F_RELATIVE_NODES.
+ MPOL_F_STATIC_NODES cannot be combined with the
+ MPOL_F_RELATIVE_NODES flag. It also cannot be used for
+ MPOL_PREFERRED policies that were created with an empty nodemask
+ (local allocation).
MPOL_F_RELATIVE_NODES: This flag specifies that the nodemask passed
by the user will be mapped relative to the set of the task or VMA's
@@ -301,7 +310,10 @@
set of memory nodes allowed by the task's cpuset, as that may
change over time.
- MPOL_F_RELATIVE_NODES cannot be used with MPOL_F_STATIC_NODES.
+ MPOL_F_RELATIVE_NODES cannot be combined with the
+ MPOL_F_STATIC_NODES flag. It also cannot be used for
+ MPOL_PREFERRED policies that were created with an empty nodemask
+ (local allocation).
MEMORY POLICY APIs