[PATCH] Memoryless nodes: use "node_memory_map" for cpuset mems_allowed validation

Lee Schermerhorn
2007-07-20T20:49:24Z

This fixes a problem I encountered testing Christoph's memoryless nodes
series. Applies atop that series. Other than this, series holds up
under what testing I've been able to do this week.

Memoryless Nodes: use "node_memory_map" for cpusets mems_allowed validation

cpusets try to ensure that any node added to a cpuset's
mems_allowed is on-line and contains memory. The assumption
was that online nodes contained memory. Thus, it is possible
to add memoryless nodes to a cpuset and then add tasks to this
cpuset. This results in continuous series of oom-kill and other
console stack traces and apparent system hang.

Change cpusets to use node_states[N_MEMORY] [a.k.a.
node_memory_map] in place of node_online_map when vetting
memories. Return error if admin attempts to write a non-empty
mems_allowed node mask containing only memoryless-nodes.

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>

kernel/cpuset.c | 33 +++++++++++++++++++++++----------
1 file changed, 23 insertions(+), 10 deletions(-)

Index: Linux/kernel/cpuset.c
===================================================================
--- Linux.orig/kernel/cpuset.c 2007-07-20 16:02:01.000000000 -0400
+++ Linux/kernel/cpuset.c 2007-07-20 16:27:46.000000000 -0400
@@ -316,26 +316,26 @@ static void guarantee_online_cpus(const

/*
* Return in *pmask the portion of a cpusets's mems_allowed that
- * are online. If none are online, walk up the cpuset hierarchy
- * until we find one that does have some online mems. If we get
- * all the way to the top and still haven't found any online mems,
- * return node_online_map.
+ * are online, with memory. If none are online with memory, walk
+ * up the cpuset hierarchy until we find one that does have some
+ * online mems. If we get all the way to the top and still haven't
+ * found any online mems, return node_states[N_MEMORY].
*
* One way or another, we guarantee to return some non-empty subset
- * of node_online_map.
+ * of node_states[N_MEMORY].
*
* Call with callback_mutex held.
*/

static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
{
- while (cs && !nodes_intersects(cs->mems_allowed, node_online_map))
+ while (cs && !nodes_intersects(cs->mems_allowed, node_states[N_MEMORY]))
cs = cs->parent;
if (cs)
- nodes_and(*pmask, cs->mems_allowed, node_online_map);
+ nodes_and(*pmask, cs->mems_allowed, node_states[N_MEMORY]);
else
- *pmask = node_online_map;
- BUG_ON(!nodes_intersects(*pmask, node_online_map));
+ *pmask = node_states[N_MEMORY];
+ BUG_ON(!nodes_intersects(*pmask, node_states[N_MEMORY]));
}

/**
@@ -623,8 +623,21 @@ static int update_nodemask(struct cpuset
retval = nodelist_parse(buf, trialcs.mems_allowed);
if (retval < 0)
goto done;
+ if (!nodes_intersects(trialcs.mems_allowed,
+ node_states[N_MEMORY])) {
+ /*
+ * error if only memoryless nodes specified.
+ */
+ retval = -ENOSPC;
+ goto done;
+ }
}
- nodes_and(trialcs.mems_allowed, trialcs.mems_allowed, node_online_map);
+ /*
+ * Exclude memoryless nodes. We know that trialcs.mems_allowed
+ * contains at least one node with memory.
+ */
+ nodes_and(trialcs.mems_allowed, trialcs.mems_allowed,
+ node_states[N_MEMORY]);
oldmem = cs->mems_allowed;
if (nodes_equal(oldmem, trialcs.mems_allowed)) {
retval = 0; /* Too easy - nothing to do */