[PATCH v3 3/9] cgroup/cpuset: Improve temporary cpumasks handling

Waiman Long
2023-06-27T00:55:23Z

The limitation that update_parent_subparts_cpumask() can only use
addmask & delmask in the given tmp cpumasks is fragile and may lead to
unexpected error.

Fix this problem by allocating/freeing a struct tmpmasks in
update_cpumask() to avoid reusing the cpumasks in trial_cs.

With this change, we can move the update_tasks_cpumask() for the
parent and update_sibling_cpumasks() for the sibling to inside
update_parent_subparts_cpumask().

Signed-off-by: Waiman Long <longman@redhat.com>
---
kernel/cgroup/cpuset.c | 42 +++++++++++++-----------------------------
1 file changed, 13 insertions(+), 29 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index ade33e50ffe2..b8ccc1be7bde 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1277,6 +1277,8 @@ enum subparts_cmd {

static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
int turning_on);
+static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
+ struct tmpmasks *tmp);

/*
* Update partition exclusive flag
@@ -1447,7 +1449,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
adding = cpumask_andnot(tmp->addmask, tmp->addmask,
parent->subparts_cpus);
/*
- * Empty cpumask is not allewed
+ * Empty cpumask is not allowed
*/
if (cpumask_empty(newmask)) {
part_error = PERR_CPUSEMPTY;
@@ -1567,8 +1569,11 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,

spin_unlock_irq(&callback_lock);

- if (adding || deleting)
+ if (adding || deleting) {
update_tasks_cpumask(parent, tmp->addmask);
+ if (parent->child_ecpus_count)
+ update_sibling_cpumasks(parent, cs, tmp);
+ }

/*
* For partcmd_update without newmask, it is being called from
@@ -1842,18 +1847,8 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
return 0;

-#ifdef CONFIG_CPUMASK_OFFSTACK
- /*
- * Use the cpumasks in trialcs for tmpmasks when they are pointers
- * to allocated cpumasks.
- *
- * Note that update_parent_subparts_cpumask() uses only addmask &
- * delmask, but not new_cpus.
- */
- tmp.addmask = trialcs->subparts_cpus;
- tmp.delmask = trialcs->effective_cpus;
- tmp.new_cpus = NULL;
-#endif
+ if (alloc_cpumasks(NULL, &tmp))
+ return -ENOMEM;

retval = validate_change(cs, trialcs);

@@ -1882,7 +1877,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
retval = 0;
}
if (retval < 0)
- return retval;
+ goto out_free;

if (cs->partition_root_state) {
if (invalidate)
@@ -1917,11 +1912,6 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
}
spin_unlock_irq(&callback_lock);

-#ifdef CONFIG_CPUMASK_OFFSTACK
- /* Now trialcs->cpus_allowed is available */
- tmp.new_cpus = trialcs->cpus_allowed;
-#endif
-
/* effective_cpus will be updated here */
update_cpumasks_hier(cs, &tmp, false);

@@ -1938,6 +1928,8 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
/* Update CS_SCHED_LOAD_BALANCE and/or sched_domains */
update_partition_sd_lb(cs, old_prs);
}
+out_free:
+ free_cpumasks(NULL, &tmp);
return 0;
}

@@ -2346,13 +2338,11 @@ static int update_prstate(struct cpuset *cs, int new_prs)

err = update_parent_subparts_cpumask(cs, partcmd_enable,
NULL, &tmpmask);
- if (err)
- goto out;
} else if (old_prs && new_prs) {
/*
* A change in load balance state only, no change in cpumasks.
*/
- goto out;
+ ;
} else {
/*
* Switching back to member is always allowed even if it
@@ -2372,12 +2362,6 @@ static int update_prstate(struct cpuset *cs, int new_prs)
spin_unlock_irq(&callback_lock);
}
}
-
- update_tasks_cpumask(parent, tmpmask.new_cpus);
-
- if (parent->child_ecpus_count)
- update_sibling_cpumasks(parent, cs, &tmpmask);
-
out:
/*
* Make partition invalid & disable CS_CPU_EXCLUSIVE if an error
--
2.31.1