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@xxxxxxxxxx>
---
This goes back to 2.6.39; but it is under DEBUG_VM, so probably
doesn't need Cc stable.
mm/memcontrol.c | 17 +----------------
1 file changed, 1 insertion(+), 16 deletions(-)
--- mmotm.orig/mm/memcontrol.c 2011-12-28 14:41:19.803018025 -0800
+++ mmotm/mm/memcontrol.c 2011-12-28 15:07:26.887055270 -0800
@@ -3369,23 +3369,8 @@ void mem_cgroup_print_bad_page(struct pa
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
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>