diff --git a/arch/x86/kernel/cpu/intel_rdt.h b/arch/x86/kernel/cpu/intel_rdt.h
index be152b3b2543..82dda4daec7f 100644
--- a/arch/x86/kernel/cpu/intel_rdt.h
+++ b/arch/x86/kernel/cpu/intel_rdt.h
@@ -33,6 +33,21 @@
 #define RMID_VAL_ERROR			BIT_ULL(63)
 #define RMID_VAL_UNAVAIL		BIT_ULL(62)
 
+
+struct rdt_fs_context {
+	struct kernfs_fs_context	kfc;
+	bool				enable_cdpl2;
+	bool				enable_cdpl3;
+	bool				enable_mba_mbps;
+};
+
+static inline struct rdt_fs_context *rdt_fc2context(struct fs_context *fc)
+{
+	struct kernfs_fs_context *kfc = fc->fs_private;
+
+	return container_of(kfc, struct rdt_fs_context, kfc);
+}
+
 DECLARE_STATIC_KEY_FALSE(rdt_enable_key);
 
 /**
diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index c74365b78253..b11d81dafa9a 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -22,6 +22,7 @@
 
 #include <linux/cpu.h>
 #include <linux/fs.h>
+#include <linux/fs_parser.h>
 #include <linux/sysfs.h>
 #include <linux/kernfs.h>
 #include <linux/seq_buf.h>
@@ -1131,43 +1132,6 @@ static void cdp_disable_all(void)
 		cdpl2_disable();
 }
 
-static int parse_rdtgroupfs_options(char *data)
-{
-	char *token, *o = data;
-	int ret = 0;
-
-	while ((token = strsep(&o, ",")) != NULL) {
-		if (!*token) {
-			ret = -EINVAL;
-			goto out;
-		}
-
-		if (!strcmp(token, "cdp")) {
-			ret = cdpl3_enable();
-			if (ret)
-				goto out;
-		} else if (!strcmp(token, "cdpl2")) {
-			ret = cdpl2_enable();
-			if (ret)
-				goto out;
-		} else if (!strcmp(token, "mba_MBps")) {
-			ret = set_mba_sc(true);
-			if (ret)
-				goto out;
-		} else {
-			ret = -EINVAL;
-			goto out;
-		}
-	}
-
-	return 0;
-
-out:
-	pr_err("Invalid mount option \"%s\"\n", token);
-
-	return ret;
-}
-
 /*
  * We don't allow rdtgroup directories to be created anywhere
  * except the root directory. Thus when looking for the rdtgroup
@@ -1236,13 +1200,27 @@ static int mkdir_mondata_all(struct kernfs_node *parent_kn,
 			     struct rdtgroup *prgrp,
 			     struct kernfs_node **mon_data_kn);
 
-static struct dentry *rdt_mount(struct file_system_type *fs_type,
-				int flags, const char *unused_dev_name,
-				void *data, size_t data_size)
+static int rdt_enable_ctx(struct rdt_fs_context *ctx)
 {
+	int ret = 0;
+
+	if (ctx->enable_cdpl2)
+		ret = cdpl2_enable();
+
+	if (!ret && ctx->enable_cdpl3)
+		ret = cdpl3_enable();
+
+	if (!ret && ctx->enable_mba_mbps)
+		ret = set_mba_sc(true);
+
+	return ret;
+}
+
+static int rdt_get_tree(struct fs_context *fc)
+{
+	struct rdt_fs_context *ctx = rdt_fc2context(fc);
 	struct rdt_domain *dom;
 	struct rdt_resource *r;
-	struct dentry *dentry;
 	int ret;
 
 	cpus_read_lock();
@@ -1251,53 +1229,42 @@ static struct dentry *rdt_mount(struct file_system_type *fs_type,
 	 * resctrl file system can only be mounted once.
 	 */
 	if (static_branch_unlikely(&rdt_enable_key)) {
-		dentry = ERR_PTR(-EBUSY);
+		ret = -EBUSY;
 		goto out;
 	}
 
-	ret = parse_rdtgroupfs_options(data);
-	if (ret) {
-		dentry = ERR_PTR(ret);
+	ret = rdt_enable_ctx(ctx);
+	if (ret < 0)
 		goto out_cdp;
-	}
 
 	closid_init();
 
 	ret = rdtgroup_create_info_dir(rdtgroup_default.kn);
-	if (ret) {
-		dentry = ERR_PTR(ret);
-		goto out_cdp;
-	}
+	if (ret < 0)
+		goto out_mba;
 
 	if (rdt_mon_capable) {
 		ret = mongroup_create_dir(rdtgroup_default.kn,
 					  NULL, "mon_groups",
 					  &kn_mongrp);
-		if (ret) {
-			dentry = ERR_PTR(ret);
+		if (ret < 0)
 			goto out_info;
-		}
 		kernfs_get(kn_mongrp);
 
 		ret = mkdir_mondata_all(rdtgroup_default.kn,
 					&rdtgroup_default, &kn_mondata);
-		if (ret) {
-			dentry = ERR_PTR(ret);
+		if (ret < 0)
 			goto out_mongrp;
-		}
 		kernfs_get(kn_mondata);
 		rdtgroup_default.mon.mon_data_kn = kn_mondata;
 	}
 
 	ret = rdt_pseudo_lock_init();
-	if (ret) {
-		dentry = ERR_PTR(ret);
+	if (ret)
 		goto out_mondata;
-	}
 
-	dentry = kernfs_mount(fs_type, flags, rdt_root,
-			      RDTGROUP_SUPER_MAGIC, NULL);
-	if (IS_ERR(dentry))
+	ret = kernfs_get_tree(fc);
+	if (ret < 0)
 		goto out_psl;
 
 	if (rdt_alloc_capable)
@@ -1326,14 +1293,98 @@ static struct dentry *rdt_mount(struct file_system_type *fs_type,
 		kernfs_remove(kn_mongrp);
 out_info:
 	kernfs_remove(kn_info);
+out_mba:
+	if (ctx->enable_mba_mbps)
+		set_mba_sc(false);
 out_cdp:
 	cdp_disable_all();
 out:
 	rdt_last_cmd_clear();
 	mutex_unlock(&rdtgroup_mutex);
 	cpus_read_unlock();
+	return ret;
+}
+
+enum rdt_param {
+	Opt_cdp,
+	Opt_cdpl2,
+	Opt_mba_mpbs,
+	nr__rdt_params
+};
+
+static const struct fs_parameter_spec rdt_param_specs[nr__rdt_params] = {
+	[Opt_cdp]	= { fs_param_takes_no_value },
+	[Opt_cdpl2]	= { fs_param_takes_no_value },
+	[Opt_mba_mpbs]	= { fs_param_takes_no_value },
+};
+
+static const struct constant_table rdt_param_keys[] = {
+	{ "cdp",	Opt_cdp },
+	{ "cdpl2",	Opt_cdpl2 },
+	{ "mba_mbps",	Opt_mba_mpbs },
+};
+
+static const struct fs_parameter_description rdt_fs_parameters = {
+	.name		= "rdt",
+	.nr_params	= nr__rdt_params,
+	.nr_keys	= ARRAY_SIZE(rdt_param_keys),
+	.keys		= rdt_param_keys,
+	.specs		= rdt_param_specs,
+	.no_source	= true,
+};
+
+static int rdt_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct rdt_fs_context *ctx = rdt_fc2context(fc);
+	struct fs_parse_result result;
+	int ret;
+
+	ret = fs_parse(fc, &rdt_fs_parameters, param, &result);
+	if (ret < 0)
+		return ret;
+
+	switch (result.key) {
+	case Opt_cdp:
+		ctx->enable_cdpl3 = true;
+		return 0;
+	case Opt_cdpl2:
+		ctx->enable_cdpl2 = true;
+		return 0;
+	case Opt_mba_mpbs:
+		ctx->enable_mba_mbps = true;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static void rdt_fs_context_free(struct fs_context *fc)
+{
+	struct rdt_fs_context *ctx = rdt_fc2context(fc);
 
-	return dentry;
+	kernfs_free_fs_context(fc);
+	kfree(ctx);
+}
+
+static const struct fs_context_operations rdt_fs_context_ops = {
+	.free		= rdt_fs_context_free,
+	.parse_param	= rdt_parse_param,
+	.get_tree	= rdt_get_tree,
+};
+
+static int rdt_init_fs_context(struct fs_context *fc, struct dentry *reference)
+{
+	struct rdt_fs_context *ctx;
+
+	ctx = kzalloc(sizeof(struct rdt_fs_context), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->kfc.root = rdt_root;
+	ctx->kfc.magic = RDTGROUP_SUPER_MAGIC;
+	fc->fs_private = &ctx->kfc;
+	fc->ops = &rdt_fs_context_ops;
+	return 0;
 }
 
 static int reset_all_ctrls(struct rdt_resource *r)
@@ -1500,9 +1551,10 @@ static void rdt_kill_sb(struct super_block *sb)
 }
 
 static struct file_system_type rdt_fs_type = {
-	.name    = "resctrl",
-	.mount   = rdt_mount,
-	.kill_sb = rdt_kill_sb,
+	.name			= "resctrl",
+	.init_fs_context	= rdt_init_fs_context,
+	.parameters		= &rdt_fs_parameters,
+	.kill_sb		= rdt_kill_sb,
 };
 
 static int mon_addfile(struct kernfs_node *parent_kn, const char *name,
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index f70e0b69e714..188c683eab14 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -22,14 +22,13 @@
 
 struct kmem_cache *kernfs_node_cache;
 
-static int kernfs_sop_remount_fs(struct super_block *sb, int *flags,
-				 char *data, size_t data_size)
+static int kernfs_sop_reconfigure(struct super_block *sb, struct fs_context *fc)
 {
 	struct kernfs_root *root = kernfs_info(sb)->root;
 	struct kernfs_syscall_ops *scops = root->syscall_ops;
 
-	if (scops && scops->remount_fs)
-		return scops->remount_fs(root, flags, data);
+	if (scops && scops->reconfigure)
+		return scops->reconfigure(root, fc);
 	return 0;
 }
 
@@ -61,7 +60,7 @@ const struct super_operations kernfs_sops = {
 	.drop_inode	= generic_delete_inode,
 	.evict_inode	= kernfs_evict_inode,
 
-	.remount_fs	= kernfs_sop_remount_fs,
+	.reconfigure	= kernfs_sop_reconfigure,
 	.show_options	= kernfs_sop_show_options,
 	.show_path	= kernfs_sop_show_path,
 };
@@ -219,7 +218,7 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
 	} while (true);
 }
 
-static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
+static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *kfc)
 {
 	struct kernfs_super_info *info = kernfs_info(sb);
 	struct inode *inode;
@@ -230,7 +229,7 @@ static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
 	sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
 	sb->s_blocksize = PAGE_SIZE;
 	sb->s_blocksize_bits = PAGE_SHIFT;
-	sb->s_magic = magic;
+	sb->s_magic = kfc->magic;
 	sb->s_op = &kernfs_sops;
 	sb->s_xattr = kernfs_xattr_handlers;
 	if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
@@ -257,21 +256,20 @@ static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
 	return 0;
 }
 
-static int kernfs_test_super(struct super_block *sb, void *data)
+static int kernfs_test_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct kernfs_super_info *sb_info = kernfs_info(sb);
-	struct kernfs_super_info *info = data;
+	struct kernfs_super_info *info = fc->s_fs_info;
 
 	return sb_info->root == info->root && sb_info->ns == info->ns;
 }
 
-static int kernfs_set_super(struct super_block *sb, void *data)
+static int kernfs_set_super(struct super_block *sb, struct fs_context *fc)
 {
-	int error;
-	error = set_anon_super(sb, data);
-	if (!error)
-		sb->s_fs_info = data;
-	return error;
+	struct kernfs_fs_context *kfc = fc->fs_private;
+
+	kfc->ns_tag = NULL;
+	return set_anon_super_fc(sb, fc);
 }
 
 /**
@@ -288,63 +286,60 @@ const void *kernfs_super_ns(struct super_block *sb)
 }
 
 /**
- * kernfs_mount_ns - kernfs mount helper
- * @fs_type: file_system_type of the fs being mounted
- * @flags: mount flags specified for the mount
- * @root: kernfs_root of the hierarchy being mounted
- * @magic: file system specific magic number
- * @new_sb_created: tell the caller if we allocated a new superblock
- * @ns: optional namespace tag of the mount
- *
- * This is to be called from each kernfs user's file_system_type->mount()
- * implementation, which should pass through the specified @fs_type and
- * @flags, and specify the hierarchy and namespace tag to mount via @root
- * and @ns, respectively.
+ * kernfs_get_tree - kernfs filesystem access/retrieval helper
+ * @fc: The filesystem context.
  *
- * The return value can be passed to the vfs layer verbatim.
+ * This is to be called from each kernfs user's fs_context->ops->get_tree()
+ * implementation, which should set the specified ->@fs_type and ->@flags, and
+ * specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
+ * respectively.
  */
-struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
-				struct kernfs_root *root, unsigned long magic,
-				bool *new_sb_created, const void *ns)
+int kernfs_get_tree(struct fs_context *fc)
 {
+	struct kernfs_fs_context *kfc = fc->fs_private;
 	struct super_block *sb;
 	struct kernfs_super_info *info;
 	int error;
 
 	info = kzalloc(sizeof(*info), GFP_KERNEL);
 	if (!info)
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 
-	info->root = root;
-	info->ns = ns;
+	info->root = kfc->root;
+	info->ns = kfc->ns_tag;
 	INIT_LIST_HEAD(&info->node);
 
-	sb = sget_userns(fs_type, kernfs_test_super, kernfs_set_super, flags,
-			 &init_user_ns, info);
-	if (IS_ERR(sb) || sb->s_fs_info != info)
-		kfree(info);
+	fc->s_fs_info = info;
+	sb = sget_fc(fc, kernfs_test_super, kernfs_set_super);
 	if (IS_ERR(sb))
-		return ERR_CAST(sb);
-
-	if (new_sb_created)
-		*new_sb_created = !sb->s_root;
+		return PTR_ERR(sb);
 
 	if (!sb->s_root) {
 		struct kernfs_super_info *info = kernfs_info(sb);
 
-		error = kernfs_fill_super(sb, magic);
+		kfc->new_sb_created = true;
+
+		error = kernfs_fill_super(sb, kfc);
 		if (error) {
 			deactivate_locked_super(sb);
-			return ERR_PTR(error);
+			return error;
 		}
 		sb->s_flags |= SB_ACTIVE;
 
 		mutex_lock(&kernfs_mutex);
-		list_add(&info->node, &root->supers);
+		list_add(&info->node, &info->root->supers);
 		mutex_unlock(&kernfs_mutex);
 	}
 
-	return dget(sb->s_root);
+	fc->root = dget(sb->s_root);
+	return 0;
+}
+
+void kernfs_free_fs_context(struct fs_context *fc)
+{
+	/* Note that we don't deal with kfc->ns_tag here. */
+	kfree(fc->s_fs_info);
+	fc->s_fs_info = NULL;
 }
 
 /**
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 77302c35b0ff..1e1c0ccc6a36 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -13,6 +13,7 @@
 #include <linux/magic.h>
 #include <linux/mount.h>
 #include <linux/init.h>
+#include <linux/slab.h>
 #include <linux/user_namespace.h>
 
 #include "sysfs.h"
@@ -20,27 +21,55 @@
 static struct kernfs_root *sysfs_root;
 struct kernfs_node *sysfs_root_kn;
 
-static struct dentry *sysfs_mount(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *data, size_t data_size)
+static int sysfs_get_tree(struct fs_context *fc)
 {
-	struct dentry *root;
-	void *ns;
-	bool new_sb = false;
+	struct kernfs_fs_context *kfc = fc->fs_private;
+	int ret;
 
-	if (!(flags & SB_KERNMOUNT)) {
+	ret = kernfs_get_tree(fc);
+	if (ret)
+		return ret;
+
+	if (kfc->new_sb_created)
+		fc->root->d_sb->s_iflags |= SB_I_USERNS_VISIBLE;
+	return 0;
+}
+
+static void sysfs_fs_context_free(struct fs_context *fc)
+{
+	struct kernfs_fs_context *kfc = fc->fs_private;
+
+	if (kfc->ns_tag)
+		kobj_ns_drop(KOBJ_NS_TYPE_NET, kfc->ns_tag);
+	kernfs_free_fs_context(fc);
+	kfree(kfc);
+}
+
+static const struct fs_context_operations sysfs_fs_context_ops = {
+	.free		= sysfs_fs_context_free,
+	.get_tree	= sysfs_get_tree,
+};
+
+static int sysfs_init_fs_context(struct fs_context *fc,
+				 struct dentry *reference)
+{
+	struct kernfs_fs_context *kfc;
+
+	if (!(fc->sb_flags & SB_KERNMOUNT)) {
 		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
-			return ERR_PTR(-EPERM);
+			return -EPERM;
 	}
 
-	ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
-	root = kernfs_mount_ns(fs_type, flags, sysfs_root,
-				SYSFS_MAGIC, &new_sb, ns);
-	if (!new_sb)
-		kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
-	else if (!IS_ERR(root))
-		root->d_sb->s_iflags |= SB_I_USERNS_VISIBLE;
+	kfc = kzalloc(sizeof(struct kernfs_fs_context), GFP_KERNEL);
+	if (!kfc)
+		return -ENOMEM;
 
-	return root;
+	kfc->ns_tag = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
+	kfc->root = sysfs_root;
+	kfc->magic = SYSFS_MAGIC;
+	fc->fs_private = kfc;
+	fc->ops = &sysfs_fs_context_ops;
+	return 0;
 }
 
 static void sysfs_kill_sb(struct super_block *sb)
@@ -52,10 +81,10 @@ static void sysfs_kill_sb(struct super_block *sb)
 }
 
 static struct file_system_type sysfs_fs_type = {
-	.name		= "sysfs",
-	.mount		= sysfs_mount,
-	.kill_sb	= sysfs_kill_sb,
-	.fs_flags	= FS_USERNS_MOUNT,
+	.name			= "sysfs",
+	.init_fs_context	= sysfs_init_fs_context,
+	.kill_sb		= sysfs_kill_sb,
+	.fs_flags		= FS_USERNS_MOUNT,
 };
 
 int __init sysfs_init(void)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c9fdf6f57913..ac198f0c466f 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -829,10 +829,11 @@ copy_cgroup_ns(unsigned long flags, struct user_namespace *user_ns,
 
 #endif /* !CONFIG_CGROUPS */
 
-static inline void get_cgroup_ns(struct cgroup_namespace *ns)
+static inline struct cgroup_namespace *get_cgroup_ns(struct cgroup_namespace *ns)
 {
 	if (ns)
 		refcount_inc(&ns->count);
+	return ns;
 }
 
 static inline void put_cgroup_ns(struct cgroup_namespace *ns)
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index ab25c8b6d9e3..627fa3956146 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -16,6 +16,7 @@
 #include <linux/rbtree.h>
 #include <linux/atomic.h>
 #include <linux/wait.h>
+#include <linux/fs_context.h>
 
 struct file;
 struct dentry;
@@ -25,6 +26,7 @@ struct vm_area_struct;
 struct super_block;
 struct file_system_type;
 
+struct kernfs_fs_context;
 struct kernfs_open_node;
 struct kernfs_iattrs;
 
@@ -166,7 +168,7 @@ struct kernfs_node {
  * kernfs_node parameter.
  */
 struct kernfs_syscall_ops {
-	int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
+	int (*reconfigure)(struct kernfs_root *root, struct fs_context *fc);
 	int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
 
 	int (*mkdir)(struct kernfs_node *parent, const char *name,
@@ -267,6 +269,18 @@ struct kernfs_ops {
 #endif
 };
 
+/*
+ * The kernfs superblock creation/mount parameter context.
+ */
+struct kernfs_fs_context {
+	struct kernfs_root	*root;		/* Root of the hierarchy being mounted */
+	void			*ns_tag;	/* Namespace tag of the mount (or NULL) */
+	unsigned long		magic;		/* File system specific magic number */
+
+	/* The following are set/used by kernfs_mount() */
+	bool			new_sb_created;	/* Set to T if we allocated a new sb */
+};
+
 #ifdef CONFIG_KERNFS
 
 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
@@ -350,9 +364,8 @@ int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
 void kernfs_notify(struct kernfs_node *kn);
 
 const void *kernfs_super_ns(struct super_block *sb);
-struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
-			       struct kernfs_root *root, unsigned long magic,
-			       bool *new_sb_created, const void *ns);
+int kernfs_get_tree(struct fs_context *fc);
+void kernfs_free_fs_context(struct fs_context *fc);
 void kernfs_kill_sb(struct super_block *sb);
 struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns);
 
@@ -454,11 +467,10 @@ static inline void kernfs_notify(struct kernfs_node *kn) { }
 static inline const void *kernfs_super_ns(struct super_block *sb)
 { return NULL; }
 
-static inline struct dentry *
-kernfs_mount_ns(struct file_system_type *fs_type, int flags,
-		struct kernfs_root *root, unsigned long magic,
-		bool *new_sb_created, const void *ns)
-{ return ERR_PTR(-ENOSYS); }
+static inline int kernfs_get_tree(struct fs_context *fc)
+{ return -ENOSYS; }
+
+static inline void kernfs_free_fs_context(struct fs_context *fc) { }
 
 static inline void kernfs_kill_sb(struct super_block *sb) { }
 
@@ -535,13 +547,4 @@ static inline int kernfs_rename(struct kernfs_node *kn,
 	return kernfs_rename_ns(kn, new_parent, new_name, NULL);
 }
 
-static inline struct dentry *
-kernfs_mount(struct file_system_type *fs_type, int flags,
-		struct kernfs_root *root, unsigned long magic,
-		bool *new_sb_created)
-{
-	return kernfs_mount_ns(fs_type, flags, root,
-				magic, new_sb_created, NULL);
-}
-
 #endif	/* __LINUX_KERNFS_H */
diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index 77ff1cd6a252..19da314b3405 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -8,6 +8,33 @@
 #include <linux/list.h>
 #include <linux/refcount.h>
 
+/*
+ * The cgroup filesystem superblock creation/mount context.
+ */
+struct cgroup_fs_context {
+	struct kernfs_fs_context kfc;
+	struct cgroup_root	*root;
+	struct cgroup_namespace	*ns;
+	u8		version;		/* cgroups version */
+	unsigned int	flags;			/* CGRP_ROOT_* flags */
+
+	/* cgroup1 bits */
+	bool		cpuset_clone_children;
+	bool		none;			/* User explicitly requested empty subsystem */
+	bool		all_ss;			/* Seen 'all' option */
+	bool		one_ss;			/* Seen 'none' option */
+	u16		subsys_mask;		/* Selected subsystems */
+	char		*name;			/* Hierarchy name */
+	char		*release_agent;		/* Path for release notifications */
+};
+
+static inline struct cgroup_fs_context *cgroup_fc2context(struct fs_context *fc)
+{
+	struct kernfs_fs_context *kfc = fc->fs_private;
+
+	return container_of(kfc, struct cgroup_fs_context, kfc);
+}
+
 /*
  * A cgroup can be associated with multiple css_sets as different tasks may
  * belong to different cgroups on different hierarchies.  In the other
@@ -89,16 +116,6 @@ struct cgroup_mgctx {
 #define DEFINE_CGROUP_MGCTX(name)						\
 	struct cgroup_mgctx name = CGROUP_MGCTX_INIT(name)
 
-struct cgroup_sb_opts {
-	u16 subsys_mask;
-	unsigned int flags;
-	char *release_agent;
-	bool cpuset_clone_children;
-	char *name;
-	/* User explicitly requested empty subsystem */
-	bool none;
-};
-
 extern struct mutex cgroup_mutex;
 extern spinlock_t css_set_lock;
 extern struct cgroup_subsys *cgroup_subsys[];
@@ -169,12 +186,10 @@ int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
 			  struct cgroup_namespace *ns);
 
 void cgroup_free_root(struct cgroup_root *root);
-void init_cgroup_root(struct cgroup_root *root, struct cgroup_sb_opts *opts);
+void init_cgroup_root(struct cgroup_fs_context *ctx);
 int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask, int ref_flags);
 int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask);
-struct dentry *cgroup_do_mount(struct file_system_type *fs_type, int flags,
-			       struct cgroup_root *root, unsigned long magic,
-			       struct cgroup_namespace *ns);
+int cgroup_do_get_tree(struct fs_context *fc);
 
 int cgroup_migrate_vet_dst(struct cgroup *dst_cgrp);
 void cgroup_migrate_finish(struct cgroup_mgctx *mgctx);
@@ -218,14 +233,15 @@ extern const struct proc_ns_operations cgroupns_operations;
  */
 extern struct cftype cgroup1_base_files[];
 extern struct kernfs_syscall_ops cgroup1_kf_syscall_ops;
+extern const struct fs_parameter_description cgroup1_fs_parameters;
 
 int proc_cgroupstats_show(struct seq_file *m, void *v);
 bool cgroup1_ssid_disabled(int ssid);
 void cgroup1_pidlist_destroy_all(struct cgroup *cgrp);
 void cgroup1_release_agent(struct work_struct *work);
 void cgroup1_check_for_release(struct cgroup *cgrp);
-struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
-			     void *data, unsigned long magic,
-			     struct cgroup_namespace *ns);
+int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param);
+int cgroup1_validate(struct fs_context *fc);
+int cgroup1_get_tree(struct fs_context *fc);
 
 #endif /* __CGROUP_INTERNAL_H */
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 8b4f0768efd6..4238a89ca721 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -13,9 +13,12 @@
 #include <linux/delayacct.h>
 #include <linux/pid_namespace.h>
 #include <linux/cgroupstats.h>
+#include <linux/fs_parser.h>
 
 #include <trace/events/cgroup.h>
 
+#define cg_invalf(fc, fmt, ...) ({ pr_err(fmt, ## __VA_ARGS__); -EINVAL; })
+
 /*
  * pidlists linger the following amount before being destroyed.  The goal
  * is avoiding frequent destruction in the middle of consecutive read calls
@@ -903,92 +906,65 @@ static int cgroup1_show_options(struct seq_file *seq, struct kernfs_root *kf_roo
 	return 0;
 }
 
-static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
-{
-	char *token, *o = data;
-	bool all_ss = false, one_ss = false;
-	u16 mask = U16_MAX;
-	struct cgroup_subsys *ss;
-	int nr_opts = 0;
-	int i;
-
-#ifdef CONFIG_CPUSETS
-	mask = ~((u16)1 << cpuset_cgrp_id);
-#endif
+enum cgroup1_param {
+	Opt_none,
+	Opt_all,
+	Opt_noprefix,
+	Opt_clone_children,
+	Opt_xattr,
+	Opt_release_agent,
+	Opt_name,
+	Opt_cpuset_v2_mode,
+	nr__cgroup1_params
+};
 
-	memset(opts, 0, sizeof(*opts));
+static const struct fs_parameter_spec cgroup1_param_specs[nr__cgroup1_params] = {
+	[Opt_all]		= { fs_param_takes_no_value },
+	[Opt_clone_children]	= { fs_param_takes_no_value },
+	[Opt_cpuset_v2_mode]	= { fs_param_takes_no_value },
+	[Opt_name]		= { fs_param_is_string },
+	[Opt_none]		= { fs_param_takes_no_value },
+	[Opt_noprefix]		= { fs_param_takes_no_value },
+	[Opt_release_agent]	= { fs_param_takes_no_value },
+	[Opt_xattr]		= { fs_param_takes_no_value },
+};
 
-	while ((token = strsep(&o, ",")) != NULL) {
-		nr_opts++;
+static const struct constant_table cgroup1_param_keys[] = {
+	{ "all",		Opt_all },
+	{ "clone_children",	Opt_clone_children },
+	{ "cpuset_v2_mode",	Opt_cpuset_v2_mode },
+	{ "name",		Opt_name },
+	{ "none",		Opt_none },
+	{ "noprefix",		Opt_noprefix },
+	{ "release_agent",	Opt_release_agent },
+	{ "xattr",		Opt_xattr },
+};
 
-		if (!*token)
-			return -EINVAL;
-		if (!strcmp(token, "none")) {
-			/* Explicitly have no subsystems */
-			opts->none = true;
-			continue;
-		}
-		if (!strcmp(token, "all")) {
-			/* Mutually exclusive option 'all' + subsystem name */
-			if (one_ss)
-				return -EINVAL;
-			all_ss = true;
-			continue;
-		}
-		if (!strcmp(token, "noprefix")) {
-			opts->flags |= CGRP_ROOT_NOPREFIX;
-			continue;
-		}
-		if (!strcmp(token, "clone_children")) {
-			opts->cpuset_clone_children = true;
-			continue;
-		}
-		if (!strcmp(token, "cpuset_v2_mode")) {
-			opts->flags |= CGRP_ROOT_CPUSET_V2_MODE;
-			continue;
-		}
-		if (!strcmp(token, "xattr")) {
-			opts->flags |= CGRP_ROOT_XATTR;
-			continue;
-		}
-		if (!strncmp(token, "release_agent=", 14)) {
-			/* Specifying two release agents is forbidden */
-			if (opts->release_agent)
-				return -EINVAL;
-			opts->release_agent =
-				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
-			if (!opts->release_agent)
-				return -ENOMEM;
-			continue;
-		}
-		if (!strncmp(token, "name=", 5)) {
-			const char *name = token + 5;
-			/* Can't specify an empty name */
-			if (!strlen(name))
-				return -EINVAL;
-			/* Must match [\w.-]+ */
-			for (i = 0; i < strlen(name); i++) {
-				char c = name[i];
-				if (isalnum(c))
-					continue;
-				if ((c == '.') || (c == '-') || (c == '_'))
-					continue;
-				return -EINVAL;
-			}
-			/* Specifying two names is forbidden */
-			if (opts->name)
-				return -EINVAL;
-			opts->name = kstrndup(name,
-					      MAX_CGROUP_ROOT_NAMELEN - 1,
-					      GFP_KERNEL);
-			if (!opts->name)
-				return -ENOMEM;
+const struct fs_parameter_description cgroup1_fs_parameters = {
+	.name		= "cgroup1",
+	.nr_params	= nr__cgroup1_params,
+	.nr_keys	= ARRAY_SIZE(cgroup1_param_keys),
+	.keys		= cgroup1_param_keys,
+	.specs		= cgroup1_param_specs,
+	.ignore_unknown	= true,
+	.no_source	= true,
+};
 
-			continue;
-		}
+int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+	struct cgroup_subsys *ss;
+	struct fs_parse_result result;
+	int ret, i;
 
+	ret = fs_parse(fc, &cgroup1_fs_parameters, param, &result);
+	if (ret < 0)
+		return ret;
+	if (ret == 0) {
+		if (strcmp(param->key, "source") == 0)
+			return 0;
 		for_each_subsys(ss, i) {
-			if (strcmp(token, ss->legacy_name))
+			if (strcmp(param->key, ss->legacy_name) != 0)
 				continue;
 			if (!cgroup_ssid_enabled(i))
 				continue;
@@ -996,75 +972,142 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 				continue;
 
 			/* Mutually exclusive option 'all' + subsystem name */
-			if (all_ss)
-				return -EINVAL;
-			opts->subsys_mask |= (1 << i);
-			one_ss = true;
+			if (ctx->all_ss)
+				return cg_invalf(fc, "cgroup1: subsys name conflicts with all");
+			ctx->subsys_mask |= (1 << i);
+			ctx->one_ss = true;
+			return 0;
+		}
 
-			break;
+		return cg_invalf(fc, "cgroup1: Unknown subsys name '%s'", param->key);
+	}
+
+	switch (result.key) {
+	case Opt_none:
+		/* Explicitly have no subsystems */
+		ctx->none = true;
+		return 0;
+	case Opt_all:
+		/* Mutually exclusive option 'all' + subsystem name */
+		if (ctx->one_ss)
+			return cg_invalf(fc, "cgroup1: all conflicts with subsys name");
+		ctx->all_ss = true;
+		return 0;
+	case Opt_noprefix:
+		ctx->flags |= CGRP_ROOT_NOPREFIX;
+		return 0;
+	case Opt_clone_children:
+		ctx->cpuset_clone_children = true;
+		return 0;
+	case Opt_cpuset_v2_mode:
+		ctx->flags |= CGRP_ROOT_CPUSET_V2_MODE;
+		return 0;
+	case Opt_xattr:
+		ctx->flags |= CGRP_ROOT_XATTR;
+		return 0;
+	case Opt_release_agent:
+		/* Specifying two release agents is forbidden */
+		if (ctx->release_agent)
+			return cg_invalf(fc, "cgroup1: release_agent respecified");
+		ctx->release_agent = param->string;
+		param->string = NULL;
+		if (!ctx->release_agent)
+			return -ENOMEM;
+		return 0;
+
+	case Opt_name:
+		/* Can't specify an empty name */
+		if (!param->size)
+			return cg_invalf(fc, "cgroup1: Empty name");
+		if (param->size > MAX_CGROUP_ROOT_NAMELEN - 1)
+			return cg_invalf(fc, "cgroup1: Name too long");
+		/* Must match [\w.-]+ */
+		for (i = 0; i < param->size; i++) {
+			char c = param->string[i];
+			if (isalnum(c))
+				continue;
+			if ((c == '.') || (c == '-') || (c == '_'))
+				continue;
+			return cg_invalf(fc, "cgroup1: Invalid name");
 		}
-		if (i == CGROUP_SUBSYS_COUNT)
-			return -ENOENT;
+		/* Specifying two names is forbidden */
+		if (ctx->name)
+			return cg_invalf(fc, "cgroup1: name respecified");
+		ctx->name = param->string;
+		param->string = NULL;
+		return 0;
 	}
 
+	return 0;
+}
+
+/*
+ * Validate the options that have been parsed.
+ */
+int cgroup1_validate(struct fs_context *fc)
+{
+	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+	struct cgroup_subsys *ss;
+	u16 mask = U16_MAX;
+	int i;
+
+#ifdef CONFIG_CPUSETS
+	mask = ~((u16)1 << cpuset_cgrp_id);
+#endif
+
 	/*
 	 * If the 'all' option was specified select all the subsystems,
 	 * otherwise if 'none', 'name=' and a subsystem name options were
 	 * not specified, let's default to 'all'
 	 */
-	if (all_ss || (!one_ss && !opts->none && !opts->name))
+	if (ctx->all_ss || (!ctx->one_ss && !ctx->none && !ctx->name))
 		for_each_subsys(ss, i)
 			if (cgroup_ssid_enabled(i) && !cgroup1_ssid_disabled(i))
-				opts->subsys_mask |= (1 << i);
+				ctx->subsys_mask |= (1 << i);
 
 	/*
 	 * We either have to specify by name or by subsystems. (So all
 	 * empty hierarchies must have a name).
 	 */
-	if (!opts->subsys_mask && !opts->name)
-		return -EINVAL;
+	if (!ctx->subsys_mask && !ctx->name)
+		return cg_invalf(fc, "cgroup1: Need name or subsystem set");
 
 	/*
 	 * Option noprefix was introduced just for backward compatibility
 	 * with the old cpuset, so we allow noprefix only if mounting just
 	 * the cpuset subsystem.
 	 */
-	if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
-		return -EINVAL;
+	if ((ctx->flags & CGRP_ROOT_NOPREFIX) && (ctx->subsys_mask & mask))
+		return cg_invalf(fc, "cgroup1: noprefix used incorrectly");
 
 	/* Can't specify "none" and some subsystems */
-	if (opts->subsys_mask && opts->none)
-		return -EINVAL;
+	if (ctx->subsys_mask && ctx->none)
+		return cg_invalf(fc, "cgroup1: none used incorrectly");
 
 	return 0;
 }
 
-static int cgroup1_remount(struct kernfs_root *kf_root, int *flags, char *data)
+static int cgroup1_reconfigure(struct kernfs_root *kf_root, struct fs_context *fc)
 {
-	int ret = 0;
+	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
 	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
-	struct cgroup_sb_opts opts;
 	u16 added_mask, removed_mask;
+	int ret = 0;
 
 	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
 
-	/* See what subsystems are wanted */
-	ret = parse_cgroupfs_options(data, &opts);
-	if (ret)
-		goto out_unlock;
-
-	if (opts.subsys_mask != root->subsys_mask || opts.release_agent)
+	if (ctx->subsys_mask != root->subsys_mask || ctx->release_agent)
 		pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
 			task_tgid_nr(current), current->comm);
 
-	added_mask = opts.subsys_mask & ~root->subsys_mask;
-	removed_mask = root->subsys_mask & ~opts.subsys_mask;
+	added_mask = ctx->subsys_mask & ~root->subsys_mask;
+	removed_mask = root->subsys_mask & ~ctx->subsys_mask;
 
 	/* Don't allow flags or name to change at remount */
-	if ((opts.flags ^ root->flags) ||
-	    (opts.name && strcmp(opts.name, root->name))) {
-		pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
-		       opts.flags, opts.name ?: "", root->flags, root->name);
+	if ((ctx->flags ^ root->flags) ||
+	    (ctx->name && strcmp(ctx->name, root->name))) {
+		cg_invalf(fc, "option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"",
+		       ctx->flags, ctx->name ?: "", root->flags, root->name);
 		ret = -EINVAL;
 		goto out_unlock;
 	}
@@ -1081,17 +1124,15 @@ static int cgroup1_remount(struct kernfs_root *kf_root, int *flags, char *data)
 
 	WARN_ON(rebind_subsystems(&cgrp_dfl_root, removed_mask));
 
-	if (opts.release_agent) {
+	if (ctx->release_agent) {
 		spin_lock(&release_agent_path_lock);
-		strcpy(root->release_agent_path, opts.release_agent);
+		strcpy(root->release_agent_path, ctx->release_agent);
 		spin_unlock(&release_agent_path_lock);
 	}
 
 	trace_cgroup_remount(root);
 
  out_unlock:
-	kfree(opts.release_agent);
-	kfree(opts.name);
 	mutex_unlock(&cgroup_mutex);
 	return ret;
 }
@@ -1099,31 +1140,26 @@ static int cgroup1_remount(struct kernfs_root *kf_root, int *flags, char *data)
 struct kernfs_syscall_ops cgroup1_kf_syscall_ops = {
 	.rename			= cgroup1_rename,
 	.show_options		= cgroup1_show_options,
-	.remount_fs		= cgroup1_remount,
+	.reconfigure		= cgroup1_reconfigure,
 	.mkdir			= cgroup_mkdir,
 	.rmdir			= cgroup_rmdir,
 	.show_path		= cgroup_show_path,
 };
 
-struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
-			     void *data, unsigned long magic,
-			     struct cgroup_namespace *ns)
+/*
+ * Find or create a v1 cgroups superblock.
+ */
+int cgroup1_get_tree(struct fs_context *fc)
 {
+	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
 	struct super_block *pinned_sb = NULL;
-	struct cgroup_sb_opts opts;
 	struct cgroup_root *root;
 	struct cgroup_subsys *ss;
-	struct dentry *dentry;
 	int i, ret;
 	bool new_root = false;
 
 	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
 
-	/* First find the desired set of subsystems */
-	ret = parse_cgroupfs_options(data, &opts);
-	if (ret)
-		goto out_unlock;
-
 	/*
 	 * Destruction of cgroup root is asynchronous, so subsystems may
 	 * still be dying after the previous unmount.  Let's drain the
@@ -1132,15 +1168,13 @@ struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
 	 * starting.  Testing ref liveliness is good enough.
 	 */
 	for_each_subsys(ss, i) {
-		if (!(opts.subsys_mask & (1 << i)) ||
+		if (!(ctx->subsys_mask & (1 << i)) ||
 		    ss->root == &cgrp_dfl_root)
 			continue;
 
 		if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) {
 			mutex_unlock(&cgroup_mutex);
-			msleep(10);
-			ret = restart_syscall();
-			goto out_free;
+			goto err_restart;
 		}
 		cgroup_put(&ss->root->cgrp);
 	}
@@ -1156,8 +1190,8 @@ struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
 		 * name matches but sybsys_mask doesn't, we should fail.
 		 * Remember whether name matched.
 		 */
-		if (opts.name) {
-			if (strcmp(opts.name, root->name))
+		if (ctx->name) {
+			if (strcmp(ctx->name, root->name))
 				continue;
 			name_match = true;
 		}
@@ -1166,15 +1200,15 @@ struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
 		 * If we asked for subsystems (or explicitly for no
 		 * subsystems) then they must match.
 		 */
-		if ((opts.subsys_mask || opts.none) &&
-		    (opts.subsys_mask != root->subsys_mask)) {
+		if ((ctx->subsys_mask || ctx->none) &&
+		    (ctx->subsys_mask != root->subsys_mask)) {
 			if (!name_match)
 				continue;
 			ret = -EBUSY;
-			goto out_unlock;
+			goto err_unlock;
 		}
 
-		if (root->flags ^ opts.flags)
+		if (root->flags ^ ctx->flags)
 			pr_warn("new mount options do not match the existing superblock, will be ignored\n");
 
 		/*
@@ -1195,11 +1229,10 @@ struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
 			mutex_unlock(&cgroup_mutex);
 			if (!IS_ERR_OR_NULL(pinned_sb))
 				deactivate_super(pinned_sb);
-			msleep(10);
-			ret = restart_syscall();
-			goto out_free;
+			goto err_restart;
 		}
 
+		ctx->root = root;
 		ret = 0;
 		goto out_unlock;
 	}
@@ -1209,41 +1242,35 @@ struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
 	 * specification is allowed for already existing hierarchies but we
 	 * can't create new one without subsys specification.
 	 */
-	if (!opts.subsys_mask && !opts.none) {
-		ret = -EINVAL;
-		goto out_unlock;
+	if (!ctx->subsys_mask && !ctx->none) {
+		ret = cg_invalf(fc, "cgroup1: No subsys list or none specified");
+		goto err_unlock;
 	}
 
 	/* Hierarchies may only be created in the initial cgroup namespace. */
-	if (ns != &init_cgroup_ns) {
+	if (ctx->ns != &init_cgroup_ns) {
 		ret = -EPERM;
-		goto out_unlock;
+		goto err_unlock;
 	}
 
 	root = kzalloc(sizeof(*root), GFP_KERNEL);
 	if (!root) {
 		ret = -ENOMEM;
-		goto out_unlock;
+		goto err_unlock;
 	}
 	new_root = true;
+	ctx->root = root;
 
-	init_cgroup_root(root, &opts);
+	init_cgroup_root(ctx);
 
-	ret = cgroup_setup_root(root, opts.subsys_mask, PERCPU_REF_INIT_DEAD);
+	ret = cgroup_setup_root(root, ctx->subsys_mask, PERCPU_REF_INIT_DEAD);
 	if (ret)
-		cgroup_free_root(root);
+		goto err_unlock;
 
 out_unlock:
 	mutex_unlock(&cgroup_mutex);
-out_free:
-	kfree(opts.release_agent);
-	kfree(opts.name);
-
-	if (ret)
-		return ERR_PTR(ret);
 
-	dentry = cgroup_do_mount(&cgroup_fs_type, flags, root,
-				 CGROUP_SUPER_MAGIC, ns);
+	ret = cgroup_do_get_tree(fc);
 
 	/*
 	 * There's a race window after we release cgroup_mutex and before
@@ -1256,6 +1283,7 @@ struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
 		percpu_ref_reinit(&root->cgrp.self.refcnt);
 		mutex_unlock(&cgroup_mutex);
 	}
+	cgroup_get(&root->cgrp);
 
 	/*
 	 * If @pinned_sb, we're reusing an existing root and holding an
@@ -1264,7 +1292,14 @@ struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
 	if (pinned_sb)
 		deactivate_super(pinned_sb);
 
-	return dentry;
+	return ret;
+
+err_restart:
+	msleep(10);
+	return restart_syscall();
+err_unlock:
+	mutex_unlock(&cgroup_mutex);
+	return ret;
 }
 
 static int __init cgroup1_wq_init(void)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index ddb1a60ae3c0..f3238f38d152 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -54,6 +54,7 @@
 #include <linux/proc_ns.h>
 #include <linux/nsproxy.h>
 #include <linux/file.h>
+#include <linux/fs_parser.h>
 #include <linux/sched/cputime.h>
 #include <net/sock.h>
 
@@ -1734,25 +1735,52 @@ int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
 	return len;
 }
 
-static int parse_cgroup_root_flags(char *data, unsigned int *root_flags)
-{
-	char *token;
+enum cgroup2_param {
+	Opt_nsdelegate,
+	nr__cgroup2_params
+};
 
-	*root_flags = 0;
+static const struct fs_parameter_spec cgroup2_param_specs[nr__cgroup2_params] = {
+	[Opt_nsdelegate]	= { fs_param_takes_no_value },
+};
 
-	if (!data)
-		return 0;
+static const struct constant_table cgroup2_param_keys[] = {
+	{ "nsdelegate",		Opt_nsdelegate },
+};
 
-	while ((token = strsep(&data, ",")) != NULL) {
-		if (!strcmp(token, "nsdelegate")) {
-			*root_flags |= CGRP_ROOT_NS_DELEGATE;
-			continue;
-		}
+static const struct fs_parameter_description cgroup2_fs_parameters = {
+	.name		= "cgroup2",
+	.nr_params	= nr__cgroup2_params,
+	.nr_keys	= ARRAY_SIZE(cgroup2_param_keys),
+	.keys		= cgroup2_param_keys,
+	.specs		= cgroup2_param_specs,
+	.no_source	= true,
+};
 
-		pr_err("cgroup2: unknown option \"%s\"\n", token);
-		return -EINVAL;
+static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+	struct fs_parse_result result;
+	int ret;
+
+	ret = fs_parse(fc, &cgroup2_fs_parameters, param, &result);
+	if (ret < 0)
+		return ret;
+
+	switch (result.key) {
+	case Opt_nsdelegate:
+		ctx->flags |= CGRP_ROOT_NS_DELEGATE;
+		return 0;
 	}
 
+	return -EINVAL;
+}
+
+static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
+{
+	if (current->nsproxy->cgroup_ns == &init_cgroup_ns &&
+	    cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE)
+		seq_puts(seq, ",nsdelegate");
 	return 0;
 }
 
@@ -1766,23 +1794,11 @@ static void apply_cgroup_root_flags(unsigned int root_flags)
 	}
 }
 
-static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
-{
-	if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE)
-		seq_puts(seq, ",nsdelegate");
-	return 0;
-}
-
-static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
+static int cgroup_reconfigure(struct kernfs_root *kf_root, struct fs_context *fc)
 {
-	unsigned int root_flags;
-	int ret;
-
-	ret = parse_cgroup_root_flags(data, &root_flags);
-	if (ret)
-		return ret;
+	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
 
-	apply_cgroup_root_flags(root_flags);
+	apply_cgroup_root_flags(ctx->flags);
 	return 0;
 }
 
@@ -1870,8 +1886,9 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
 	INIT_WORK(&cgrp->release_agent_work, cgroup1_release_agent);
 }
 
-void init_cgroup_root(struct cgroup_root *root, struct cgroup_sb_opts *opts)
+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);
@@ -1880,12 +1897,12 @@ void init_cgroup_root(struct cgroup_root *root, struct cgroup_sb_opts *opts)
 	init_cgroup_housekeeping(cgrp);
 	idr_init(&root->cgroup_idr);
 
-	root->flags = opts->flags;
-	if (opts->release_agent)
-		strscpy(root->release_agent_path, opts->release_agent, PATH_MAX);
-	if (opts->name)
-		strscpy(root->name, opts->name, MAX_CGROUP_ROOT_NAMELEN);
-	if (opts->cpuset_clone_children)
+	root->flags = ctx->flags;
+	if (ctx->release_agent)
+		strscpy(root->release_agent_path, ctx->release_agent, PATH_MAX);
+	if (ctx->name)
+		strscpy(root->name, ctx->name, MAX_CGROUP_ROOT_NAMELEN);
+	if (ctx->cpuset_clone_children)
 		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
 }
 
@@ -1990,57 +2007,53 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask, int ref_flags)
 	return ret;
 }
 
-struct dentry *cgroup_do_mount(struct file_system_type *fs_type, int flags,
-			       struct cgroup_root *root, unsigned long magic,
-			       struct cgroup_namespace *ns)
+int cgroup_do_get_tree(struct fs_context *fc)
 {
-	struct dentry *dentry;
-	bool new_sb;
+	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+	int ret;
 
-	dentry = kernfs_mount(fs_type, flags, root->kf_root, magic, &new_sb);
+	ctx->kfc.root = ctx->root->kf_root;
+
+	ret = kernfs_get_tree(fc);
+	if (ret < 0)
+		goto out_cgrp;
 
 	/*
 	 * In non-init cgroup namespace, instead of root cgroup's dentry,
 	 * we return the dentry corresponding to the cgroupns->root_cgrp.
 	 */
-	if (!IS_ERR(dentry) && ns != &init_cgroup_ns) {
+	if (ctx->ns != &init_cgroup_ns) {
 		struct dentry *nsdentry;
 		struct cgroup *cgrp;
 
 		mutex_lock(&cgroup_mutex);
 		spin_lock_irq(&css_set_lock);
 
-		cgrp = cset_cgroup_from_root(ns->root_cset, root);
+		cgrp = cset_cgroup_from_root(ctx->ns->root_cset, ctx->root);
 
 		spin_unlock_irq(&css_set_lock);
 		mutex_unlock(&cgroup_mutex);
 
-		nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);
-		dput(dentry);
-		dentry = nsdentry;
+		nsdentry = kernfs_node_dentry(cgrp->kn, fc->root->d_sb);
+		if (IS_ERR(nsdentry))
+			return PTR_ERR(nsdentry);
+		dput(fc->root);
+		fc->root = nsdentry;
 	}
 
-	if (IS_ERR(dentry) || !new_sb)
-		cgroup_put(&root->cgrp);
+	ret = 0;
+	if (ctx->kfc.new_sb_created)
+		goto out_cgrp;
+	apply_cgroup_root_flags(ctx->flags);
+	return 0;
 
-	return dentry;
+out_cgrp:
+	return ret;
 }
 
-static struct dentry *cgroup_mount(struct file_system_type *fs_type,
-			 int flags, const char *unused_dev_name,
-			 void *data, size_t data_size)
+static int cgroup_get_tree(struct fs_context *fc)
 {
-	struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
-	struct dentry *dentry;
-	int ret;
-
-	get_cgroup_ns(ns);
-
-	/* Check if the caller has permission to mount. */
-	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) {
-		put_cgroup_ns(ns);
-		return ERR_PTR(-EPERM);
-	}
+	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
 
 	/*
 	 * The first time anyone tries to mount a cgroup, enable the list
@@ -2049,29 +2062,87 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
 	if (!use_task_css_set_links)
 		cgroup_enable_task_cg_lists();
 
-	if (fs_type == &cgroup2_fs_type) {
-		unsigned int root_flags;
-
-		ret = parse_cgroup_root_flags(data, &root_flags);
-		if (ret) {
-			put_cgroup_ns(ns);
-			return ERR_PTR(ret);
-		}
+	switch (ctx->version) {
+	case 1:
+		return cgroup1_get_tree(fc);
 
+	case 2:
 		cgrp_dfl_visible = true;
 		cgroup_get_live(&cgrp_dfl_root.cgrp);
 
-		dentry = cgroup_do_mount(&cgroup2_fs_type, flags, &cgrp_dfl_root,
-					 CGROUP2_SUPER_MAGIC, ns);
-		if (!IS_ERR(dentry))
-			apply_cgroup_root_flags(root_flags);
-	} else {
-		dentry = cgroup1_mount(&cgroup_fs_type, flags, data,
-				       CGROUP_SUPER_MAGIC, ns);
+		ctx->root = &cgrp_dfl_root;
+		return cgroup_do_get_tree(fc);
+
+	default:
+		BUG();
 	}
+}
+
+static int cgroup_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+
+	if (ctx->version == 1)
+		return cgroup1_parse_param(fc, param);
+
+	return cgroup2_parse_param(fc, param);
+}
+
+static int cgroup_validate(struct fs_context *fc)
+{
+	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+
+	if (ctx->version == 1)
+		return cgroup1_validate(fc);
+	return 0;
+}
 
-	put_cgroup_ns(ns);
-	return dentry;
+/*
+ * Destroy a cgroup filesystem context.
+ */
+static void cgroup_fs_context_free(struct fs_context *fc)
+{
+	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+
+	kfree(ctx->name);
+	kfree(ctx->release_agent);
+	if (ctx->root)
+		cgroup_put(&ctx->root->cgrp);
+	put_cgroup_ns(ctx->ns);
+	kernfs_free_fs_context(fc);
+	kfree(ctx);
+}
+
+static const struct fs_context_operations cgroup_fs_context_ops = {
+	.free		= cgroup_fs_context_free,
+	.parse_param	= cgroup_parse_param,
+	.validate	= cgroup_validate,
+	.get_tree	= cgroup_get_tree,
+};
+
+/*
+ * Initialise the cgroup filesystem creation/reconfiguration context.  Notably,
+ * we select the namespace we're going to use.
+ */
+static int cgroup_init_fs_context(struct fs_context *fc, struct dentry *reference)
+{
+	struct cgroup_fs_context *ctx;
+	struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
+
+	/* Check if the caller has permission to mount. */
+	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
+		return -EPERM;
+
+	ctx = kzalloc(sizeof(struct cgroup_fs_context), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->ns = get_cgroup_ns(ns);
+	ctx->version = (fc->fs_type == &cgroup2_fs_type) ? 2 : 1;
+	ctx->kfc.magic = (ctx->version == 2) ? CGROUP2_SUPER_MAGIC : CGROUP_SUPER_MAGIC;
+	fc->fs_private = &ctx->kfc;
+	fc->ops = &cgroup_fs_context_ops;
+	return 0;
 }
 
 static void cgroup_kill_sb(struct super_block *sb)
@@ -2096,17 +2167,19 @@ static void cgroup_kill_sb(struct super_block *sb)
 }
 
 struct file_system_type cgroup_fs_type = {
-	.name = "cgroup",
-	.mount = cgroup_mount,
-	.kill_sb = cgroup_kill_sb,
-	.fs_flags = FS_USERNS_MOUNT,
+	.name			= "cgroup",
+	.init_fs_context	= cgroup_init_fs_context,
+	.parameters		= &cgroup1_fs_parameters,
+	.kill_sb		= cgroup_kill_sb,
+	.fs_flags		= FS_USERNS_MOUNT,
 };
 
 static struct file_system_type cgroup2_fs_type = {
-	.name = "cgroup2",
-	.mount = cgroup_mount,
-	.kill_sb = cgroup_kill_sb,
-	.fs_flags = FS_USERNS_MOUNT,
+	.name			= "cgroup2",
+	.init_fs_context	= cgroup_init_fs_context,
+	.parameters		= &cgroup2_fs_parameters,
+	.kill_sb		= cgroup_kill_sb,
+	.fs_flags		= FS_USERNS_MOUNT,
 };
 
 int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
@@ -5175,7 +5248,7 @@ int cgroup_rmdir(struct kernfs_node *kn)
 
 static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
 	.show_options		= cgroup_show_options,
-	.remount_fs		= cgroup_remount,
+	.reconfigure		= cgroup_reconfigure,
 	.mkdir			= cgroup_mkdir,
 	.rmdir			= cgroup_rmdir,
 	.show_path		= cgroup_show_path,
@@ -5242,11 +5315,12 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
  */
 int __init cgroup_init_early(void)
 {
-	static struct cgroup_sb_opts __initdata opts;
+	static struct cgroup_fs_context __initdata ctx;
 	struct cgroup_subsys *ss;
 	int i;
 
-	init_cgroup_root(&cgrp_dfl_root, &opts);
+	ctx.root = &cgrp_dfl_root;
+	init_cgroup_root(&ctx);
 	cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF;
 
 	RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index e6582b2f5144..b02161a41d5a 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -324,10 +324,8 @@ static int cpuset_get_tree(struct fs_context *fc)
 	int ret = -ENODEV;
 
 	cgroup_fs = get_fs_type("cgroup");
-	if (cgroup_fs) {
-		ret = PTR_ERR(cgroup_fs);
+	if (!cgroup_fs)
 		goto out;
-	}
 
 	cg_fc = vfs_new_fs_context(cgroup_fs, NULL, fc->sb_flags, fc->purpose);
 	put_filesystem(cgroup_fs);
