diff options
| author | Muchun Song <songmuchun@bytedance.com> | 2022-06-21 20:56:54 +0800 |
|---|---|---|
| committer | Liam R. Howlett <Liam.Howlett@oracle.com> | 2022-07-19 20:15:10 -0400 |
| commit | 767659716821896a5ea98d7810c13d08ab51db21 (patch) | |
| tree | 7e7adb27eee756782a5ae44e1184b82f595d3fe5 /include/trace/events/writeback.h | |
| parent | a4b9f84659ff4125077727b7b4581bb94bfb2482 (diff) | |
mm: memcontrol: make all the callers of {folio,page}_memcg() safe
When we use objcg APIs to charge the LRU pages, the page will not hold a
reference to the memcg associated with the page. So the caller of the
{folio,page}_memcg() should hold an rcu read lock or obtain a reference to
the memcg associated with the page to protect memcg from being released.
So introduce get_mem_cgroup_from_{page,folio}() to obtain a reference to
the memory cgroup associated with the page.
In this patch, make all the callers hold an rcu read lock or obtain a
reference to the memcg to protect memcg from being released when the LRU
pages reparented.
We do not need to adjust the callers of {folio,page}_memcg() during the
whole process of mem_cgroup_move_task(). Because the cgroup migration and
memory cgroup offlining are serialized by @cgroup_mutex. In this routine,
the LRU pages cannot be reparented to its parent memory cgroup. So
{folio,page}_memcg() is stable and cannot be released.
This is a preparation for reparenting the LRU pages.
Link: https://lkml.kernel.org/r/20220621125658.64935-8-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include/trace/events/writeback.h')
| -rw-r--r-- | include/trace/events/writeback.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h index 86b2a82da546..cdb822339f13 100644 --- a/include/trace/events/writeback.h +++ b/include/trace/events/writeback.h @@ -258,6 +258,11 @@ TRACE_EVENT(track_foreign_dirty, __entry->ino = inode ? inode->i_ino : 0; __entry->memcg_id = wb->memcg_css->id; __entry->cgroup_ino = __trace_wb_assign_cgroup(wb); + /* + * TP_fast_assign() is under preemption disabled which can + * serve as an RCU read-side critical section so that the + * memcg returned by folio_memcg() cannot be freed. + */ __entry->page_cgroup_ino = cgroup_ino(folio_memcg(folio)->css.cgroup); ), |