在 2020/11/25 上午1:59, Lorenzo Stoakes 写道:
> On Tue, 24 Nov 2020 at 07:54, syzbot
> <syzbot+ce635500093181f39c1c@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>> syzbot found the following issue on:
>>
>> HEAD commit: d9137320 Add linux-next specific files for 20201124
>
> This appears to be a product of 4b2904f3 ("mm/memcg: add missed
> warning in mem_cgroup_lruvec") adding a VM_WARN_ON_ONCE() to
> mem_cgroup_lruvec, which when invoked from a function other than
> mem_cgroup_page_lruvec() can in fact be called with the condition
> false.
> If we move the check back into mem_cgroup_page_lruvec() it resolves
> the issue. I enclose a simple version of this below, happy to submit
> as a proper patch if this is the right approach:
>
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 87ed56dc75f9..27cc40a490b2 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -618,7 +618,6 @@ static inline struct lruvec
> *mem_cgroup_lruvec(struct mem_cgroup *memcg,
> goto out;
> }
>
> - VM_WARN_ON_ONCE(!memcg);
> if (!memcg)
> memcg = root_mem_cgroup;
>
> @@ -645,6 +644,7 @@ static inline struct lruvec
> *mem_cgroup_lruvec(struct mem_cgroup *memcg,
> static inline struct lruvec *mem_cgroup_page_lruvec(struct page *page,
> struct pglist_data *pgdat)
> {
> + VM_WARN_ON_ONCE_PAGE(!page_memcg(page), page);
> return mem_cgroup_lruvec(page_memcg(page), pgdat);
> }
>
Acked.
Right. Would you like to remove the bad commit 4b2904f3 ("mm/memcg: add missed
warning in mem_cgroup_lruvec") and replace yours.
and further more, could you like try another patch?
Thanks
Alex
>From 073b222bd06a96c39656b0460c705e48c7eedafc Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Date: Wed, 25 Nov 2020 14:06:33 +0800
Subject: [PATCH] mm/memcg: bail out early when !memcg in mem_cgroup_lruvec
In some scenarios, we call NULL memcg in mem_cgroup_lruvec(NULL, pgdat)
so we could get out early to skip unnecessary check.
Also warning if both parameter are NULL.
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 3a995bb3157f..5e4da83eb9ce 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -613,7 +613,9 @@ static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg,
struct mem_cgroup_per_node *mz;
struct lruvec *lruvec;
- if (mem_cgroup_disabled()) {
+ VM_WARN_ON_ONCE(!memcg && !pgdat);
+
+ if (mem_cgroup_disabled() || !memcg) {
lruvec = &pgdat->__lruvec;
goto out;
}
--
2.29.GIT
