cpusets: restructure the function update_cpumask() and update_nodemask()

Extract two functions from update_cpumask() and update_nodemask().They
will be used later for updating tasks' cpus_allowed and mems_allowed after
CPU/NODE offline/online.

[lizf@cn.fujitsu.com: build fix]
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Acked-by: Paul Jackson <pj@sgi.com>
Cc: David Rientjes <rientjes@google.com>
Cc:  Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 109 insertions, 72 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 276ce7e4f1ab..7326d51eefe1 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -764,6 +764,37 @@ static void cpuset_change_cpumask(struct task_struct *tsk,
 }
 
 /**
+ * update_tasks_cpumask - Update the cpumasks of tasks in the cpuset.
+ * @cs: the cpuset in which each task's cpus_allowed mask needs to be changed
+ *
+ * Called with cgroup_mutex held
+ *
+ * The cgroup_scan_tasks() function will scan all the tasks in a cgroup,
+ * calling callback functions for each.
+ *
+ * Return 0 if successful, -errno if not.
+ */
+static int update_tasks_cpumask(struct cpuset *cs)
+{
+        struct cgroup_scanner scan;
+        struct ptr_heap heap;
+        int retval;
+
+        retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, &started_after);
+        if (retval)
+                return retval;
+
+        scan.cg = cs->css.cgroup;
+        scan.test_task = cpuset_test_cpumask;
+        scan.process_task = cpuset_change_cpumask;
+        scan.heap = &heap;
+        retval = cgroup_scan_tasks(&scan);
+
+        heap_free(&heap);
+        return retval;
+}
+
+/**
  * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
  * @cs: the cpuset to consider
  * @buf: buffer of cpu numbers written to this cpuset
@@ -771,8 +802,6 @@ static void cpuset_change_cpumask(struct task_struct *tsk,
 static int update_cpumask(struct cpuset *cs, const char *buf)
 {
         struct cpuset trialcs;
-        struct cgroup_scanner scan;
-        struct ptr_heap heap;
         int retval;
         int is_load_balanced;
 
@@ -806,10 +835,6 @@ static int update_cpumask(struct cpuset *cs, const char *buf)
         if (cpus_equal(cs->cpus_allowed, trialcs.cpus_allowed))
                 return 0;
 
-        retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, &started_after);
-        if (retval)
-                return retval;
-
         is_load_balanced = is_sched_load_balance(&trialcs);
 
         mutex_lock(&callback_mutex);
@@ -820,12 +845,9 @@ static int update_cpumask(struct cpuset *cs, const char *buf)
          * Scan tasks in the cpuset, and update the cpumasks of any
          * that need an update.
          */
-        scan.cg = cs->css.cgroup;
-        scan.test_task = cpuset_test_cpumask;
-        scan.process_task = cpuset_change_cpumask;
-        scan.heap = &heap;
-        cgroup_scan_tasks(&scan);
-        heap_free(&heap);
+        retval = update_tasks_cpumask(cs);
+        if (retval < 0)
+                return retval;
 
         if (is_load_balanced)
                 rebuild_sched_domains();
@@ -881,73 +903,25 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
         mutex_unlock(&callback_mutex);
 }
 
-/*
- * Handle user request to change the 'mems' memory placement
- * of a cpuset.  Needs to validate the request, update the
- * cpusets mems_allowed and mems_generation, and for each
- * task in the cpuset, rebind any vma mempolicies and if
- * the cpuset is marked 'memory_migrate', migrate the tasks
- * pages to the new memory.
- *
- * Call with cgroup_mutex held.  May take callback_mutex during call.
- * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
- * lock each such tasks mm->mmap_sem, scan its vma's and rebind
- * their mempolicies to the cpusets new mems_allowed.
- */
-
 static void *cpuset_being_rebound;
 
-static int update_nodemask(struct cpuset *cs, const char *buf)
+/**
+ * update_tasks_nodemask - Update the nodemasks of tasks in the cpuset.
+ * @cs: the cpuset in which each task's mems_allowed mask needs to be changed
+ * @oldmem: old mems_allowed of cpuset cs
+ *
+ * Called with cgroup_mutex held
+ * Return 0 if successful, -errno if not.
+ */
+static int update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem)
 {
-        struct cpuset trialcs;
-        nodemask_t oldmem;
         struct task_struct *p;
         struct mm_struct **mmarray;
         int i, n, ntasks;
         int migrate;
         int fudge;
-        int retval;
         struct cgroup_iter it;
-
-        /*
-         * top_cpuset.mems_allowed tracks node_stats[N_HIGH_MEMORY];
-         * it's read-only
-         */
-        if (cs == &top_cpuset)
-                return -EACCES;
-
-        trialcs = *cs;
-
-        /*
-         * 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
-         * with tasks have memory.
-         */
-        if (!*buf) {
-                nodes_clear(trialcs.mems_allowed);
-        } else {
-                retval = nodelist_parse(buf, trialcs.mems_allowed);
-                if (retval < 0)
-                        goto done;
-
-                if (!nodes_subset(trialcs.mems_allowed,
-                                node_states[N_HIGH_MEMORY]))
-                        return -EINVAL;
-        }
-        oldmem = cs->mems_allowed;
-        if (nodes_equal(oldmem, trialcs.mems_allowed)) {
-                retval = 0;             /* Too easy - nothing to do */
-                goto done;
-        }
-        retval = validate_change(cs, &trialcs);
-        if (retval < 0)
-                goto done;
-
-        mutex_lock(&callback_mutex);
-        cs->mems_allowed = trialcs.mems_allowed;
-        cs->mems_generation = cpuset_mems_generation++;
-        mutex_unlock(&callback_mutex);
+        int retval;
 
         cpuset_being_rebound = cs;              /* causes mpol_dup() rebind */
 
@@ -1014,7 +988,7 @@ static int update_nodemask(struct cpuset *cs, const char *buf)
 
                 mpol_rebind_mm(mm, &cs->mems_allowed);
                 if (migrate)
-                        cpuset_migrate_mm(mm, &oldmem, &cs->mems_allowed);
+                        cpuset_migrate_mm(mm, oldmem, &cs->mems_allowed);
                 mmput(mm);
         }
 
@@ -1026,6 +1000,70 @@ done:
         return retval;
 }
 
+/*
+ * Handle user request to change the 'mems' memory placement
+ * of a cpuset.  Needs to validate the request, update the
+ * cpusets mems_allowed and mems_generation, and for each
+ * task in the cpuset, rebind any vma mempolicies and if
+ * the cpuset is marked 'memory_migrate', migrate the tasks
+ * pages to the new memory.
+ *
+ * Call with cgroup_mutex held.  May take callback_mutex during call.
+ * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
+ * lock each such tasks mm->mmap_sem, scan its vma's and rebind
+ * their mempolicies to the cpusets new mems_allowed.
+ */
+static int update_nodemask(struct cpuset *cs, const char *buf)
+{
+        struct cpuset trialcs;
+        nodemask_t oldmem;
+        int retval;
+
+        /*
+         * top_cpuset.mems_allowed tracks node_stats[N_HIGH_MEMORY];
+         * it's read-only
+         */
+        if (cs == &top_cpuset)
+                return -EACCES;
+
+        trialcs = *cs;
+
+        /*
+         * 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
+         * with tasks have memory.
+         */
+        if (!*buf) {
+                nodes_clear(trialcs.mems_allowed);
+        } else {
+                retval = nodelist_parse(buf, trialcs.mems_allowed);
+                if (retval < 0)
+                        goto done;
+
+                if (!nodes_subset(trialcs.mems_allowed,
+                                node_states[N_HIGH_MEMORY]))
+                        return -EINVAL;
+        }
+        oldmem = cs->mems_allowed;
+        if (nodes_equal(oldmem, trialcs.mems_allowed)) {
+                retval = 0;             /* Too easy - nothing to do */
+                goto done;
+        }
+        retval = validate_change(cs, &trialcs);
+        if (retval < 0)
+                goto done;
+
+        mutex_lock(&callback_mutex);
+        cs->mems_allowed = trialcs.mems_allowed;
+        cs->mems_generation = cpuset_mems_generation++;
+        mutex_unlock(&callback_mutex);
+
+        retval = update_tasks_nodemask(cs, &oldmem);
+done:
+        return retval;
+}
+
 int current_cpuset_is_being_rebound(void)
 {
         return task_cs(current) == cpuset_being_rebound;
@@ -1935,7 +1973,6 @@ void __init cpuset_init_smp(void)
 }
 
 /**
-
  * cpuset_cpus_allowed - return cpus_allowed mask from a tasks cpuset.
  * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed.
  * @pmask: pointer to cpumask_t variable to receive cpus_allowed set.