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memcg: fix mem_cgroup_print_bad_page

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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 <hughd@google.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2012-01-12 17:19:54 -08:00 committed by Linus Torvalds
parent 12d2710786
commit 90b3feaec8
1 changed files with 1 additions and 16 deletions
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17
mm/memcontrol.c
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@ -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