From c00c4cd077833f566bc20a5c9cadb9c4f7d77bf6 Mon Sep 17 00:00:00 2001 From: Sasha Levin Date: Mon, 23 Sep 2024 04:47:41 -0400 Subject: [PATCH] Fixes for 5.10 Signed-off-by: Sasha Levin --- ...ations-on-the-cgroup-root_list-rcu-s.patch | 122 ++++++++++++++++++ queue-5.10/series | 1 + 2 files changed, 123 insertions(+) create mode 100644 queue-5.10/cgroup-make-operations-on-the-cgroup-root_list-rcu-s.patch 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 index 00000000000..af808e01852 --- /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 +Date: Sun, 29 Oct 2023 06:14:29 +0000 +Subject: cgroup: Make operations on the cgroup root_list RCU safe + +From: Yafang Shao + +[ 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 +Signed-off-by: Tejun Heo +Signed-off-by: Sasha Levin +--- + 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 2a92cd74142..97654cdc462 100644 --- 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 -- 2.47.3