Commit 010cfac4 authored by Li Zefan's avatar Li Zefan Committed by Linus Torvalds
Browse files

cpuset: avoid changing cpuset's mems when errno returned 



When writing to cpuset.mems, cpuset has to update its mems_allowed before
calling update_tasks_nodemask(), but this function might return -ENOMEM.

To avoid this rare case, we allocate the memory before changing
mems_allowed, and then pass to update_tasks_nodemask().  Similar to what
update_cpumask() does.

Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3b6766fe

kernel/cpuset.c

+16 −9
Original line number Diff line number Diff line
@@ -1057,13 +1057,15 @@ static void *cpuset_being_rebound; 
 * 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

 * @heap: if NULL, defer allocating heap memory to cgroup_scan_tasks()

 *

 * Called with cgroup_mutex held

 * Return 0 if successful, -errno if not.

 * No return value. It's guaranteed that cgroup_scan_tasks() always returns 0

 * if @heap != NULL.

 */

static int update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem)

static void update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem,

				 struct ptr_heap *heap)

{

	int retval;

	struct cgroup_scanner scan;



	cpuset_being_rebound = cs;		/* causes mpol_dup() rebind */
@@ -1071,7 +1073,7 @@ static int update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem) 
	scan.cg = cs->css.cgroup;

	scan.test_task = NULL;

	scan.process_task = cpuset_change_nodemask;

	scan.heap = NULL;

	scan.heap = heap;

	scan.data = (nodemask_t *)oldmem;



	/*
@@ -1084,12 +1086,10 @@ static int update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem) 
	 * It's ok if we rebind the same mm twice; mpol_rebind_mm()

	 * is idempotent.  Also migrate pages in each mm to new nodes.

	 */

	retval = cgroup_scan_tasks(&scan);

	cgroup_scan_tasks(&scan);



	/* We're done rebinding vmas to this cpuset's new mems_allowed. */

	cpuset_being_rebound = NULL;



	return retval;

}



/*
@@ -1110,6 +1110,7 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs, 
{

	nodemask_t oldmem;

	int retval;

	struct ptr_heap heap;



	/*

	 * top_cpuset.mems_allowed tracks node_stats[N_HIGH_MEMORY];
@@ -1144,12 +1145,18 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs, 
	if (retval < 0)

		goto done;



	retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);

	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);

	update_tasks_nodemask(cs, &oldmem, &heap);



	heap_free(&heap);

done:

	return retval;

}
@@ -2003,7 +2010,7 @@ static void scan_for_empty_cpusets(struct cpuset *root) 
			remove_tasks_in_empty_cpuset(cp);

		else {

			update_tasks_cpumask(cp, NULL);

			update_tasks_nodemask(cp, &oldmems);

			update_tasks_nodemask(cp, &oldmems, NULL);

		}

	}

}

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