At present, top_cpuset.mems_allowed is same as node_states[N_MEMORY] and it
cannot be changed at the runtime. Maximum possible node_states[N_MEMORY]
also gets reflected in top_cpuset.effective_mems interface. It prevents some
one from removing or restricting memory placement which will be applicable
system wide on a given memory node through cpuset mechanism which might be
limiting. This solves the problem by enabling update_nodemask() function to
accept changes to top_cpuset.mems_allowed as well. Once changed, it also
updates the value of top_cpuset.effective_mems. Updates all it's task's
mems_allowed nodemask as well. It calls cpuset_inc() to make sure cpuset
is accounted for in the buddy allocator through cpusets_enabled() check.
Signed-off-by: Anshuman Khandual <khand...@linux.vnet.ibm.com>
---
Tested for
* Enforcement of changed top_cpuset.mems_allowed
* Global mems_allowed cannot be changed till there are other
cpusets present underneath the top root cpuset. I guess it
is expected.
kernel/cpuset.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index b308888..e8c105a 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1210,15 +1210,6 @@ static int update_nodemask(struct cpuset *cs, struct
cpuset *trialcs,
int retval;
/*
- * top_cpuset.mems_allowed tracks node_stats[N_MEMORY];
- * it's read-only
- */
- if (cs == &top_cpuset) {
- retval = -EACCES;
- goto done;
- }
-
- /*
* An empty mems_allowed is ok iff there are no tasks in the cpuset.
* Since nodelist_parse() fails on an empty mask, we special case
* that parsing. The validate_change() call ensures that cpusets
@@ -1232,7 +1223,7 @@ static int update_nodemask(struct cpuset *cs, struct
cpuset *trialcs,
goto done;
if (!nodes_subset(trialcs->mems_allowed,
- top_cpuset.mems_allowed)) {
+ node_states[N_MEMORY])) {
retval = -EINVAL;
goto done;
}
@@ -1250,6 +1241,16 @@ static int update_nodemask(struct cpuset *cs, struct
cpuset *trialcs,
cs->mems_allowed = trialcs->mems_allowed;
spin_unlock_irq(&callback_lock);
+ if (cs == &top_cpuset) {
+ spin_lock_irq(&callback_lock);
+ cs->effective_mems = trialcs->mems_allowed;
+ spin_unlock_irq(&callback_lock);
+
+ update_tasks_nodemask(cs);
+ cpuset_inc();
+ goto done;
+ }
+
/* use trialcs->mems_allowed as a temp variable */
update_nodemasks_hier(cs, &trialcs->mems_allowed);
done:
--
1.8.3.1
