From: Waiman Long longman@redhat.com
stable inclusion from stable-v6.6.47 commit f3c60ab676bb62e01d004d5b1cf2963a296c8e6a category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IAP55A
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit a7fb0423c201ba12815877a0b5a68a6a1710b23a upstream.
Commit 331654dc5f40 ("cgroup: Make operations on the cgroup root_list RCU safe") adds a new rcu_head to the cgroup_root structure and kvfree_rcu() for freeing the cgroup_root.
The current implementation of kvfree_rcu(), however, has the limitation that the offset of the rcu_head structure within the larger data structure must be less than 4096 or the compilation will fail. See the macro definition of __is_kvfree_rcu_offset() in include/linux/rcupdate.h for more information.
By putting rcu_head below the large cgroup structure, any change to the cgroup structure that makes it larger run the risk of causing build failure under certain configurations. Commit 77070eeb8821 ("cgroup: Avoid false cacheline sharing of read mostly rstat_cpu") happens to be the last straw that breaks it. Fix this problem by moving the rcu_head structure up before the cgroup structure.
Fixes: 331654dc5f40 ("cgroup: Make operations on the cgroup root_list RCU safe") Reported-by: Stephen Rothwell sfr@canb.auug.org.au Closes: https://lore.kernel.org/lkml/20231207143806.114e0a74@canb.auug.org.au/ Signed-off-by: Waiman Long longman@redhat.com Acked-by: Yafang Shao laoar.shao@gmail.com Reviewed-by: Yosry Ahmed yosryahmed@google.com Reviewed-by: Michal Koutný mkoutny@suse.com Signed-off-by: Tejun Heo tj@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Conflicts: include/linux/cgroup-defs.h [Context is mismatched for wait_queue_head_t wait was merged] Signed-off-by: Chen Ridong chenridong@huawei.com --- include/linux/cgroup-defs.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 05ece896af7d..8eb518ce87a1 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -573,6 +573,10 @@ struct cgroup_root { /* Unique id for this hierarchy. */ int hierarchy_id;
+ /* A list running through the active hierarchies */ + struct list_head root_list; + struct rcu_head rcu; /* Must be near the top */ + /* * The root cgroup. The containing cgroup_root will be destroyed on its * release. cgrp->ancestors[0] will be used overflowing into the @@ -589,10 +593,6 @@ struct cgroup_root { /* Wait while cgroups are being destroyed */ wait_queue_head_t wait;
- /* A list running through the active hierarchies */ - struct list_head root_list; - struct rcu_head rcu; - /* Hierarchy-specific flags */ unsigned int flags;