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'
  ...

1 files changed, 33 insertions, 11 deletions

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 1358c21837f1..5124e196c2bf 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -145,8 +145,10 @@ static struct dentry *kernfs_fh_to_parent(struct super_block *sb,
 static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
 {
 	struct kernfs_node *kn = kernfs_dentry_node(child);
+	struct kernfs_root *root = kernfs_root(kn);
 
-	return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
+	guard(rwsem_read)(&root->kernfs_rwsem);
+	return d_obtain_alias(kernfs_get_inode(child->d_sb, kernfs_parent(kn)));
 }
 
 static const struct export_operations kernfs_export_ops = {
@@ -186,10 +188,10 @@ static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
 		return NULL;
 	}
 
-	while (child->parent != parent) {
-		if (!child->parent)
+	while (kernfs_parent(child) != parent) {
+		child = kernfs_parent(child);
+		if (!child)
 			return NULL;
-		child = child->parent;
 	}
 
 	return child;
@@ -207,16 +209,27 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
 {
 	struct dentry *dentry;
 	struct kernfs_node *knparent;
+	struct kernfs_root *root;
 
 	BUG_ON(sb->s_op != &kernfs_sops);
 
 	dentry = dget(sb->s_root);
 
 	/* Check if this is the root kernfs_node */
-	if (!kn->parent)
+	if (!rcu_access_pointer(kn->__parent))
 		return dentry;
 
-	knparent = find_next_ancestor(kn, NULL);
+	root = kernfs_root(kn);
+	/*
+	 * As long as kn is valid, its parent can not vanish. This is cgroup's
+	 * kn so it can't have its parent replaced. Therefore it is safe to use
+	 * the ancestor node outside of the RCU or locked section.
+	 */
+	if (WARN_ON_ONCE(!(root->flags & KERNFS_ROOT_INVARIANT_PARENT)))
+		return ERR_PTR(-EINVAL);
+	scoped_guard(rcu) {
+		knparent = find_next_ancestor(kn, NULL);
+	}
 	if (WARN_ON(!knparent)) {
 		dput(dentry);
 		return ERR_PTR(-EINVAL);
@@ -225,17 +238,26 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
 	do {
 		struct dentry *dtmp;
 		struct kernfs_node *kntmp;
+		const char *name;
 
 		if (kn == knparent)
 			return dentry;
-		kntmp = find_next_ancestor(kn, knparent);
-		if (WARN_ON(!kntmp)) {
+
+		scoped_guard(rwsem_read, &root->kernfs_rwsem) {
+			kntmp = find_next_ancestor(kn, knparent);
+			if (WARN_ON(!kntmp)) {
+				dput(dentry);
+				return ERR_PTR(-EINVAL);
+			}
+			name = kstrdup(kernfs_rcu_name(kntmp), GFP_KERNEL);
+		}
+		if (!name) {
 			dput(dentry);
-			return ERR_PTR(-EINVAL);
+			return ERR_PTR(-ENOMEM);
 		}
-		dtmp = lookup_positive_unlocked(kntmp->name, dentry,
-					       strlen(kntmp->name));
+		dtmp = lookup_positive_unlocked(name, dentry, strlen(name));
 		dput(dentry);
+		kfree(name);
 		if (IS_ERR(dtmp))
 			return dtmp;
 		knparent = kntmp;