This patch reverts 2ad306b17c0a ("fork: protect architectures where
THREAD_SIZE >= PAGE_SIZE against fork bombs").
The reasoning behind this is that charging thread_info is the last piece
that prevents us from reparenting kmemcg on css offline. The point is
that we can't reliably track all thread_info pages accounted to a
particular cgroup, because (a) it is freed in __put_task_struct and (b)
on exit tasks are moved to the root cgroup. That said, given a cgroup
there is no sane way to find all tasks (including zombies) that charged
thread_info to this cgroup. Of course, we could uncharge thread_info on
task exit, but that wouldn't help us against fork bombs. So revert and
forget about this.
Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Glauber Costa <glommer@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxxx>
---
include/linux/thread_info.h | 2 --
kernel/fork.c | 4 ++--
2 files changed, 2 insertions(+), 4 deletions(-)
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index fddbe2023a5d..1807bb194816 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -61,8 +61,6 @@ extern long do_no_restart_syscall(struct restart_block *parm);
# define THREADINFO_GFP (GFP_KERNEL | __GFP_NOTRACK)
#endif
-#define THREADINFO_GFP_ACCOUNTED (THREADINFO_GFP | __GFP_KMEMCG)
-
/*
* flag set/clear/test wrappers
* - pass TIF_xxxx constants to these functions
diff --git a/kernel/fork.c b/kernel/fork.c
index ea1bb6a54823..c22bdaa5db4e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -150,7 +150,7 @@ void __weak arch_release_thread_info(struct thread_info *ti)
static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
int node)
{
- struct page *page = alloc_pages_node(node, THREADINFO_GFP_ACCOUNTED,
+ struct page *page = alloc_pages_node(node, THREADINFO_GFP,
THREAD_SIZE_ORDER);
return page ? page_address(page) : NULL;
@@ -158,7 +158,7 @@ static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
static inline void free_thread_info(struct thread_info *ti)
{
- free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
+ free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
}
# else
static struct kmem_cache *thread_info_cache;
--
1.7.10.4
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