Kmemleak could quickly fail to allocate an object structure and then disable itself in a low-memory situation. For example, running a mmap() workload triggering swapping and OOM [1]. Kmemleak allocation could fail even though the trackig object is succeeded. Hence, it could still try to start a direct reclaim if it is not executed in an atomic context (spinlock, irq-handler etc), or a high-priority allocation in an atomic context as a last-ditch effort. [1] https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/mem/oom/oom01.c Signed-off-by: Qian Cai <cai@xxxxxx> --- v2: remove the needless checking for NULL objects in slab_post_alloc_hook() pointed out by Catalin. mm/kmemleak.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/mm/kmemleak.c b/mm/kmemleak.c index f9d9dc250428..9e1aa3b7df75 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -576,6 +576,16 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size, struct rb_node **link, *rb_parent; object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp)); +#ifdef CONFIG_PREEMPT_COUNT + if (!object) { + /* last-ditch effort in a low-memory situation */ + if (irqs_disabled() || is_idle_task(current) || in_atomic()) + gfp = GFP_ATOMIC; + else + gfp = gfp_kmemleak_mask(gfp) | __GFP_DIRECT_RECLAIM; + object = kmem_cache_alloc(object_cache, gfp); + } +#endif if (!object) { pr_warn("Cannot allocate a kmemleak_object structure\n"); kmemleak_disable(); -- 2.17.2 (Apple Git-113)
