Merge tag 'driver-core-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core updatesk from Greg KH:
 "Here is the big set of driver core updates for 6.15-rc1. Lots of stuff
  happened this development cycle, including:

   - kernfs scaling changes to make it even faster thanks to rcu

   - bin_attribute constify work in many subsystems

   - faux bus minor tweaks for the rust bindings

   - rust binding updates for driver core, pci, and platform busses,
     making more functionaliy available to rust drivers. These are all
     due to people actually trying to use the bindings that were in
     6.14.

   - make Rafael and Danilo full co-maintainers of the driver core
     codebase

   - other minor fixes and updates"

* tag 'driver-core-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (52 commits)
  rust: platform: require Send for Driver trait implementers
  rust: pci: require Send for Driver trait implementers
  rust: platform: impl Send + Sync for platform::Device
  rust: pci: impl Send + Sync for pci::Device
  rust: platform: fix unrestricted &mut platform::Device
  rust: pci: fix unrestricted &mut pci::Device
  rust: device: implement device context marker
  rust: pci: use to_result() in enable_device_mem()
  MAINTAINERS: driver core: mark Rafael and Danilo as co-maintainers
  rust/kernel/faux: mark Registration methods inline
  driver core: faux: only create the device if probe() succeeds
  rust/faux: Add missing parent argument to Registration::new()
  rust/faux: Drop #[repr(transparent)] from faux::Registration
  rust: io: fix devres test with new io accessor functions
  rust: io: rename `io::Io` accessors
  kernfs: Move dput() outside of the RCU section.
  efi: rci2: mark bin_attribute as __ro_after_init
  rapidio: constify 'struct bin_attribute'
  firmware: qemu_fw_cfg: constify 'struct bin_attribute'
  powerpc/perf/hv-24x7: Constify 'struct bin_attribute'
  ...

3 files changed, 21 insertions, 7 deletions

diff --git a/kernel/Kconfig.hz b/kernel/Kconfig.hz
index 38ef6d06888e..ce1435cb08b1 100644
--- a/kernel/Kconfig.hz
+++ b/kernel/Kconfig.hz
@@ -30,7 +30,7 @@ choice
 	 250 Hz is a good compromise choice allowing server performance
 	 while also showing good interactive responsiveness even
 	 on SMP and NUMA systems. If you are going to be using NTSC video
-	 or multimedia, selected 300Hz instead.
+	 or multimedia, select 300Hz instead.
 
 	config HZ_300
 		bool "300 HZ"
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 11ea8d24ac72..fa24c032ed6f 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -851,7 +851,7 @@ static int cgroup1_rename(struct kernfs_node *kn, struct kernfs_node *new_parent
 
 	if (kernfs_type(kn) != KERNFS_DIR)
 		return -ENOTDIR;
-	if (kn->parent != new_parent)
+	if (rcu_access_pointer(kn->__parent) != new_parent)
 		return -EIO;
 
 	/*
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index f231fe3a0744..ac2db99941ca 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -633,9 +633,22 @@ int cgroup_task_count(const struct cgroup *cgrp)
 	return count;
 }
 
+static struct cgroup *kn_priv(struct kernfs_node *kn)
+{
+	struct kernfs_node *parent;
+	/*
+	 * The parent can not be replaced due to KERNFS_ROOT_INVARIANT_PARENT.
+	 * Therefore it is always safe to dereference this pointer outside of a
+	 * RCU section.
+	 */
+	parent = rcu_dereference_check(kn->__parent,
+				       kernfs_root_flags(kn) & KERNFS_ROOT_INVARIANT_PARENT);
+	return parent->priv;
+}
+
 struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
 {
-	struct cgroup *cgrp = of->kn->parent->priv;
+	struct cgroup *cgrp = kn_priv(of->kn);
 	struct cftype *cft = of_cft(of);
 
 	/*
@@ -1612,7 +1625,7 @@ void cgroup_kn_unlock(struct kernfs_node *kn)
 	if (kernfs_type(kn) == KERNFS_DIR)
 		cgrp = kn->priv;
 	else
-		cgrp = kn->parent->priv;
+		cgrp = kn_priv(kn);
 
 	cgroup_unlock();
 
@@ -1644,7 +1657,7 @@ struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn, bool drain_offline)
 	if (kernfs_type(kn) == KERNFS_DIR)
 		cgrp = kn->priv;
 	else
-		cgrp = kn->parent->priv;
+		cgrp = kn_priv(kn);
 
 	/*
 	 * We're gonna grab cgroup_mutex which nests outside kernfs
@@ -2118,7 +2131,8 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
 	root->kf_root = kernfs_create_root(kf_sops,
 					   KERNFS_ROOT_CREATE_DEACTIVATED |
 					   KERNFS_ROOT_SUPPORT_EXPORTOP |
-					   KERNFS_ROOT_SUPPORT_USER_XATTR,
+					   KERNFS_ROOT_SUPPORT_USER_XATTR |
+					   KERNFS_ROOT_INVARIANT_PARENT,
 					   root_cgrp);
 	if (IS_ERR(root->kf_root)) {
 		ret = PTR_ERR(root->kf_root);
@@ -4115,7 +4129,7 @@ static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
 				 size_t nbytes, loff_t off)
 {
 	struct cgroup_file_ctx *ctx = of->priv;
-	struct cgroup *cgrp = of->kn->parent->priv;
+	struct cgroup *cgrp = kn_priv(of->kn);
 	struct cftype *cft = of_cft(of);
 	struct cgroup_subsys_state *css;
 	int ret;