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Subject[PATCH 3/6] cpuset: convert cpuset_attach() to use cpumask_var_t
Impact: reduce stack usage

Allocate a cpumask_var_t in cpuset_can_attach() and then use it in
cpuset_attach(), so we won't fail cpuset_attach().

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
kernel/cpuset.c | 31 +++++++++++++++++++++++++------
1 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index afa29cf..b4c36d5 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1306,6 +1306,14 @@ static int fmeter_getrate(struct fmeter *fmp)
return val;
}

+/*
+ * Since cpuset_attach() can't fail, we allocate a cpumask_var_t in
+ * cpuset_can_attach() and then use it in cpuset_attach().
+ *
+ * Protected by cgroup_lock.
+ */
+static cpumask_var_t cpus_attach;
+
/* Called by cgroups to determine if a cpuset is usable; cgroup_mutex held */
static int cpuset_can_attach(struct cgroup_subsys *ss,
struct cgroup *cont, struct task_struct *tsk)
@@ -1321,16 +1329,25 @@ static int cpuset_can_attach(struct cgroup_subsys *ss,
if (!cpus_equal(tsk->cpus_allowed, cs->cpus_allowed))
ret = -EINVAL;
mutex_unlock(&callback_mutex);
+
+ if (ret)
+ return ret;
}

- return ret < 0 ? ret : security_task_setscheduler(tsk, 0, NULL);
+ ret = security_task_setscheduler(tsk, 0, NULL);
+ if (ret)
+ return ret;
+
+ if (!alloc_cpumask_var(&cpus_attach, GFP_KERNEL))
+ return -ENOMEM;
+
+ return 0;
}

static void cpuset_attach(struct cgroup_subsys *ss,
struct cgroup *cont, struct cgroup *oldcont,
struct task_struct *tsk)
{
- cpumask_t cpus;
nodemask_t from, to;
struct mm_struct *mm;
struct cpuset *cs = cgroup_cs(cont);
@@ -1338,15 +1355,15 @@ static void cpuset_attach(struct cgroup_subsys *ss,
int err;

if (cs == &top_cpuset) {
- cpus = cpu_possible_map;
+ cpumask_copy(cpus_attach, cpu_possible_mask);
} else {
mutex_lock(&callback_mutex);
- guarantee_online_cpus(cs, &cpus);
+ guarantee_online_cpus(cs, cpus_attach);
mutex_unlock(&callback_mutex);
}
- err = set_cpus_allowed_ptr(tsk, &cpus);
+ err = set_cpus_allowed_ptr(tsk, cpus_attach);
if (err)
- return;
+ goto out;

from = oldcs->mems_allowed;
to = cs->mems_allowed;
@@ -1358,6 +1375,8 @@ static void cpuset_attach(struct cgroup_subsys *ss,
mmput(mm);
}

+out:
+ free_cpumask_var(cpus_attach);
}

/* The various types of files and directories in a cpuset file system */
--
1.5.4.rc3



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