From 90b3feaec8ffb167abd8903bf111605c2f035aa8 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Thu, 12 Jan 2012 17:19:54 -0800 Subject: [PATCH] memcg: fix mem_cgroup_print_bad_page If DEBUG_VM, mem_cgroup_print_bad_page() is called whenever bad_page() shows a "Bad page state" message, removes page from circulation, adds a taint and continues. This is at a very low level, often when a spinlock is held (sometimes when page table lock is held, for example). We want to recover from this badness, not make it worse: we must not kmalloc memory here, we must not do a cgroup path lookup via dubious pointers. No doubt that code was useful to debug a particular case at one time, and may be again, but take it out of the mainline kernel. Signed-off-by: Hugh Dickins Cc: Daisuke Nishimura Cc: KAMEZAWA Hiroyuki Cc: Johannes Weiner Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 9f2f64697409..602207be9853 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3364,23 +3364,8 @@ void mem_cgroup_print_bad_page(struct page *page) pc = lookup_page_cgroup_used(page); if (pc) { - int ret = -1; - char *path; - - printk(KERN_ALERT "pc:%p pc->flags:%lx pc->mem_cgroup:%p", + printk(KERN_ALERT "pc:%p pc->flags:%lx pc->mem_cgroup:%p\n", pc, pc->flags, pc->mem_cgroup); - - path = kmalloc(PATH_MAX, GFP_KERNEL); - if (path) { - rcu_read_lock(); - ret = cgroup_path(pc->mem_cgroup->css.cgroup, - path, PATH_MAX); - rcu_read_unlock(); - } - - printk(KERN_CONT "(%s)\n", - (ret < 0) ? "cannot get the path" : path); - kfree(path); } } #endif -- 2.30.2