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-rw-r--r--kernel/cpuset.c90
1 files changed, 90 insertions, 0 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 6004719f26e..19f87565be1 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -812,12 +812,24 @@ static int update_cpumask(struct cpuset *cs, char *buf)
}
/*
+ * 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.
+ *
* Call with manage_sem held. May take callback_sem 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, char *buf)
{
struct cpuset trialcs;
+ struct task_struct *g, *p;
+ struct mm_struct **mmarray;
+ int i, n, ntasks;
+ int fudge;
int retval;
trialcs = *cs;
@@ -839,6 +851,76 @@ static int update_nodemask(struct cpuset *cs, char *buf)
cs->mems_generation = atomic_read(&cpuset_mems_generation);
up(&callback_sem);
+ set_cpuset_being_rebound(cs); /* causes mpol_copy() rebind */
+
+ fudge = 10; /* spare mmarray[] slots */
+ fudge += cpus_weight(cs->cpus_allowed); /* imagine one fork-bomb/cpu */
+ retval = -ENOMEM;
+
+ /*
+ * Allocate mmarray[] to hold mm reference for each task
+ * in cpuset cs. Can't kmalloc GFP_KERNEL while holding
+ * tasklist_lock. We could use GFP_ATOMIC, but with a
+ * few more lines of code, we can retry until we get a big
+ * enough mmarray[] w/o using GFP_ATOMIC.
+ */
+ while (1) {
+ ntasks = atomic_read(&cs->count); /* guess */
+ ntasks += fudge;
+ mmarray = kmalloc(ntasks * sizeof(*mmarray), GFP_KERNEL);
+ if (!mmarray)
+ goto done;
+ write_lock_irq(&tasklist_lock); /* block fork */
+ if (atomic_read(&cs->count) <= ntasks)
+ break; /* got enough */
+ write_unlock_irq(&tasklist_lock); /* try again */
+ kfree(mmarray);
+ }
+
+ n = 0;
+
+ /* Load up mmarray[] with mm reference for each task in cpuset. */
+ do_each_thread(g, p) {
+ struct mm_struct *mm;
+
+ if (n >= ntasks) {
+ printk(KERN_WARNING
+ "Cpuset mempolicy rebind incomplete.\n");
+ continue;
+ }
+ if (p->cpuset != cs)
+ continue;
+ mm = get_task_mm(p);
+ if (!mm)
+ continue;
+ mmarray[n++] = mm;
+ } while_each_thread(g, p);
+ write_unlock_irq(&tasklist_lock);
+
+ /*
+ * Now that we've dropped the tasklist spinlock, we can
+ * rebind the vma mempolicies of each mm in mmarray[] to their
+ * new cpuset, and release that mm. The mpol_rebind_mm()
+ * call takes mmap_sem, which we couldn't take while holding
+ * tasklist_lock. Forks can happen again now - the mpol_copy()
+ * cpuset_being_rebound check will catch such forks, and rebind
+ * their vma mempolicies too. Because we still hold the global
+ * cpuset manage_sem, we know that no other rebind effort will
+ * be contending for the global variable cpuset_being_rebound.
+ * It's ok if we rebind the same mm twice; mpol_rebind_mm()
+ * is idempotent.
+ */
+ for (i = 0; i < n; i++) {
+ struct mm_struct *mm = mmarray[i];
+
+ mpol_rebind_mm(mm, &cs->mems_allowed);
+ mmput(mm);
+ }
+
+ /* We're done rebinding vma's to this cpusets new mems_allowed. */
+ kfree(mmarray);
+ set_cpuset_being_rebound(NULL);
+ retval = 0;
done:
return retval;
}
@@ -1011,6 +1093,7 @@ static int attach_task(struct cpuset *cs, char *pidbuf, char **ppathbuf)
struct cpuset *oldcs;
cpumask_t cpus;
nodemask_t from, to;
+ struct mm_struct *mm;
if (sscanf(pidbuf, "%d", &pid) != 1)
return -EIO;
@@ -1060,6 +1143,13 @@ static int attach_task(struct cpuset *cs, char *pidbuf, char **ppathbuf)
to = cs->mems_allowed;
up(&callback_sem);
+
+ mm = get_task_mm(tsk);
+ if (mm) {
+ mpol_rebind_mm(mm, &to);
+ mmput(mm);
+ }
+
if (is_memory_migrate(cs))
do_migrate_pages(tsk->mm, &from, &to, MPOL_MF_MOVE_ALL);
put_task_struct(tsk);