Fixes for 5.10

Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/queue-5.10/cgroup-make-operations-on-the-cgroup-root_list-rcu-s.patch b/queue-5.10/cgroup-make-operations-on-the-cgroup-root_list-rcu-s.patch
new file mode 100644 (file)
index 0000000..af808e0
--- /dev/null
+++ b/queue-5.10/cgroup-make-operations-on-the-cgroup-root_list-rcu-s.patch
@@ -0,0 +1,122 @@
+From 5d77b33fb5d57c6bd0848c810974dff0b0649b63 Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Sun, 29 Oct 2023 06:14:29 +0000
+Subject: cgroup: Make operations on the cgroup root_list RCU safe
+
+From: Yafang Shao <laoar.shao@gmail.com>
+
+[ Upstream commit d23b5c577715892c87533b13923306acc6243f93 ]
+
+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
+the cgroup_mutex during traversal. Modifications to the list only occur in
+the cgroup root setup and destroy paths, which should be infrequent in a
+production environment. In contrast, traversal may occur frequently.
+Therefore, making it RCU-safe would be beneficial.
+
+Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
+Signed-off-by: Tejun Heo <tj@kernel.org>
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ include/linux/cgroup-defs.h     |  1 +
+ kernel/cgroup/cgroup-internal.h |  3 ++-
+ kernel/cgroup/cgroup.c          | 14 +++++++-------
+ 3 files changed, 10 insertions(+), 8 deletions(-)
+
+diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
+index 6c6323a01d430..e0e03c68000f0 100644
+--- a/include/linux/cgroup-defs.h
++++ b/include/linux/cgroup-defs.h
+@@ -512,6 +512,7 @@ struct cgroup_root {
+ 
+       /* A list running through the active hierarchies */
+       struct list_head root_list;
++      struct rcu_head rcu;
+ 
+       /* Hierarchy-specific flags */
+       unsigned int flags;
+diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
+index d8fcc139ac05d..f38f56b8cc416 100644
+--- a/kernel/cgroup/cgroup-internal.h
++++ b/kernel/cgroup/cgroup-internal.h
+@@ -172,7 +172,8 @@ extern struct list_head cgroup_roots;
+ 
+ /* iterate across the hierarchies */
+ #define for_each_root(root)                                           \
+-      list_for_each_entry((root), &cgroup_roots, root_list)
++      list_for_each_entry_rcu((root), &cgroup_roots, root_list,       \
++                              lockdep_is_held(&cgroup_mutex))
+ 
+ /**
+  * for_each_subsys - iterate all enabled cgroup subsystems
+diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
+index 643d8e178f7b9..66970b74106c8 100644
+--- a/kernel/cgroup/cgroup.c
++++ b/kernel/cgroup/cgroup.c
+@@ -1304,7 +1304,7 @@ static void cgroup_exit_root_id(struct cgroup_root *root)
+ 
+ void cgroup_free_root(struct cgroup_root *root)
+ {
+-      kfree(root);
++      kfree_rcu(root, rcu);
+ }
+ 
+ static void cgroup_destroy_root(struct cgroup_root *root)
+@@ -1337,7 +1337,7 @@ static void cgroup_destroy_root(struct cgroup_root *root)
+       spin_unlock_irq(&css_set_lock);
+ 
+       if (!list_empty(&root->root_list)) {
+-              list_del(&root->root_list);
++              list_del_rcu(&root->root_list);
+               cgroup_root_count--;
+       }
+ 
+@@ -1382,7 +1382,6 @@ current_cgns_cgroup_from_root(struct cgroup_root *root)
+       }
+       rcu_read_unlock();
+ 
+-      BUG_ON(!res);
+       return res;
+ }
+ 
+@@ -1392,7 +1391,6 @@ 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) {
+@@ -1418,7 +1416,9 @@ 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.
++ * called with css_set_lock held to prevent task's groups from being modified.
++ * Must be called with either cgroup_mutex or rcu read lock to prevent the
++ * cgroup root from being destroyed.
+  */
+ struct cgroup *task_cgroup_from_root(struct task_struct *task,
+                                    struct cgroup_root *root)
+@@ -1950,7 +1950,7 @@ void init_cgroup_root(struct cgroup_fs_context *ctx)
+       struct cgroup_root *root = ctx->root;
+       struct cgroup *cgrp = &root->cgrp;
+ 
+-      INIT_LIST_HEAD(&root->root_list);
++      INIT_LIST_HEAD_RCU(&root->root_list);
+       atomic_set(&root->nr_cgrps, 1);
+       cgrp->root = root;
+       init_cgroup_housekeeping(cgrp);
+@@ -2028,7 +2028,7 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
+        * care of subsystems' refcounts, which are explicitly dropped in
+        * the failure exit path.
+        */
+-      list_add(&root->root_list, &cgroup_roots);
++      list_add_rcu(&root->root_list, &cgroup_roots);
+       cgroup_root_count++;
+ 
+       /*
+-- 
+2.43.0
+

diff --git a/queue-5.10/series b/queue-5.10/series
index 2a92cd74142fce4a25a894f51b7821a8319ab776..97654cdc46202508698f6ee8178c336b6e7fe949 100644 (file)
--- a/queue-5.10/series
+++ b/queue-5.10/series
@@ -56,3 +56,4 @@ spi-bcm63xx-enable-module-autoloading.patch-29644
 x86-hyperv-set-x86_feature_tsc_known_freq-when-hyper.patch-3718
 ocfs2-add-bounds-checking-to-ocfs2_xattr_find_entry.patch-28208
 ocfs2-strict-bound-check-before-memcmp-in-ocfs2_xatt.patch-28181
+cgroup-make-operations-on-the-cgroup-root_list-rcu-s.patch