[ Sasha's backport helper bot ]
Hi,
The upstream commit SHA1 provided is correct: d23b5c577715892c87533b13923306acc6243f93
WARNING: Author mismatch between patch and upstream commit:
Backport author: Siddh Raman Pant <siddh.raman.pant@xxxxxxxxxx>
Commit author: Yafang Shao <laoar.shao@xxxxxxxxx>
Status in newer kernel trees:
6.12.y | Present (exact SHA1)
6.11.y | Present (exact SHA1)
6.6.y | Present (different SHA1: dd9542ae7c7c)
6.1.y | Present (different SHA1: f5b7a9792041)
5.15.y | Present (different SHA1: de77545c72c4)
5.10.y | Present (different SHA1: 45a81667e0e8)
5.4.y | Not found
Note: The patch differs from the upstream commit:
---
1: d23b5c5777158 ! 1: ab0b59573d9f9 cgroup: Make operations on the cgroup root_list RCU safe
@@ Metadata
## Commit message ##
cgroup: Make operations on the cgroup root_list RCU safe
+ commit d23b5c577715892c87533b13923306acc6243f93 upstream.
+
At present, when we perform operations on the cgroup root_list, we must
hold the cgroup_mutex, which is a relatively heavyweight lock. In reality,
we can make operations on this list RCU-safe, eliminating the need to hold
@@ Commit message
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
+ [fp: adapt to 5.10 mainly because of changes made by e210a89f5b07
+ ("cgroup.c: add helper __cset_cgroup_from_root to cleanup duplicated
+ codes")]
+ Signed-off-by: Fedor Pchelkin <pchelkin@xxxxxxxxx>
+ [Shivani: Modified to apply on v5.4.y]
+ Signed-off-by: Shivani Agarwal <shivani.agarwal@xxxxxxxxxxxx>
+ Reviewed-by: Siddh Raman Pant <siddh.raman.pant@xxxxxxxxxx>
+ Signed-off-by: Siddh Raman Pant <siddh.raman.pant@xxxxxxxxxx>
## include/linux/cgroup-defs.h ##
@@ include/linux/cgroup-defs.h: struct cgroup_root {
@@ kernel/cgroup/cgroup-internal.h: extern struct list_head cgroup_roots;
* for_each_subsys - iterate all enabled cgroup subsystems
## kernel/cgroup/cgroup.c ##
-@@ kernel/cgroup/cgroup.c: static void cgroup_exit_root_id(struct cgroup_root *root)
-
- void cgroup_free_root(struct cgroup_root *root)
+@@ kernel/cgroup/cgroup.c: void cgroup_free_root(struct cgroup_root *root)
{
-- kfree(root);
-+ kfree_rcu(root, rcu);
+ if (root) {
+ idr_destroy(&root->cgroup_idr);
+- kfree(root);
++ kfree_rcu(root, rcu);
+ }
}
- static void cgroup_destroy_root(struct cgroup_root *root)
@@ kernel/cgroup/cgroup.c: static void cgroup_destroy_root(struct cgroup_root *root)
spin_unlock_irq(&css_set_lock);
- WARN_ON_ONCE(list_empty(&root->root_list));
-- list_del(&root->root_list);
-+ list_del_rcu(&root->root_list);
- cgroup_root_count--;
+ if (!list_empty(&root->root_list)) {
+- list_del(&root->root_list);
++ list_del_rcu(&root->root_list);
+ cgroup_root_count--;
+ }
- if (!have_favordynmods)
-@@ kernel/cgroup/cgroup.c: static inline struct cgroup *__cset_cgroup_from_root(struct css_set *cset,
+@@ kernel/cgroup/cgroup.c: static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
+ {
+ struct cgroup *res = NULL;
+
+- lockdep_assert_held(&cgroup_mutex);
+ lockdep_assert_held(&css_set_lock);
+
+ if (cset == &init_css_set) {
+@@ kernel/cgroup/cgroup.c: static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
}
}
-- BUG_ON(!res_cgroup);
+- BUG_ON(!res);
+ /*
+ * If cgroup_mutex is not held, the cgrp_cset_link will be freed
+ * before we remove the cgroup root from the root_list. Consequently,
@@ kernel/cgroup/cgroup.c: static inline struct cgroup *__cset_cgroup_from_root(str
+ * If we don't hold cgroup_mutex in the caller, we must do the NULL
+ * check.
+ */
- return res_cgroup;
+ return res;
}
-@@ kernel/cgroup/cgroup.c: static struct cgroup *current_cgns_cgroup_dfl(void)
- static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
- struct cgroup_root *root)
- {
-- lockdep_assert_held(&cgroup_mutex);
- lockdep_assert_held(&css_set_lock);
-
- return __cset_cgroup_from_root(cset, root);
-@@ kernel/cgroup/cgroup.c: static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
-
/*
* Return the cgroup for "task" from the given hierarchy. Must be
- * called with cgroup_mutex and css_set_lock held.
---
Results of testing on various branches:
| Branch | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.4.y | Success | Success |
