Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs mount updates from Al Viro:
 "The first part of mount updates.

  Convert filesystems to use the new mount API"

* 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (63 commits)
  mnt_init(): call shmem_init() unconditionally
  constify ksys_mount() string arguments
  don't bother with registering rootfs
  init_rootfs(): don't bother with init_ramfs_fs()
  vfs: Convert smackfs to use the new mount API
  vfs: Convert selinuxfs to use the new mount API
  vfs: Convert securityfs to use the new mount API
  vfs: Convert apparmorfs to use the new mount API
  vfs: Convert openpromfs to use the new mount API
  vfs: Convert xenfs to use the new mount API
  vfs: Convert gadgetfs to use the new mount API
  vfs: Convert oprofilefs to use the new mount API
  vfs: Convert ibmasmfs to use the new mount API
  vfs: Convert qib_fs/ipathfs to use the new mount API
  vfs: Convert efivarfs to use the new mount API
  vfs: Convert configfs to use the new mount API
  vfs: Convert binfmt_misc to use the new mount API
  convenience helper: get_tree_single()
  convenience helper get_tree_nodev()
  vfs: Kill sget_userns()
  ...

23 files changed, 252 insertions, 229 deletions

diff --git a/fs/aio.c b/fs/aio.c
index 8b3aa2739906..01e0fb9ae45a 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -42,6 +42,7 @@
 #include <linux/ramfs.h>
 #include <linux/percpu-refcount.h>
 #include <linux/mount.h>
+#include <linux/pseudo_fs.h>
 
 #include <asm/kmap_types.h>
 #include <linux/uaccess.h>
@@ -249,15 +250,12 @@ static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages)
 	return file;
 }
 
-static struct dentry *aio_mount(struct file_system_type *fs_type,
-				int flags, const char *dev_name, void *data)
+static int aio_init_fs_context(struct fs_context *fc)
 {
-	struct dentry *root = mount_pseudo(fs_type, "aio:", NULL, NULL,
-					   AIO_RING_MAGIC);
-
-	if (!IS_ERR(root))
-		root->d_sb->s_iflags |= SB_I_NOEXEC;
-	return root;
+	if (!init_pseudo(fc, AIO_RING_MAGIC))
+		return -ENOMEM;
+	fc->s_iflags |= SB_I_NOEXEC;
+	return 0;
 }
 
 /* aio_setup
@@ -268,7 +266,7 @@ static int __init aio_setup(void)
 {
 	static struct file_system_type aio_fs = {
 		.name		= "aio",
-		.mount		= aio_mount,
+		.init_fs_context = aio_init_fs_context,
 		.kill_sb	= kill_anon_super,
 	};
 	aio_mnt = kern_mount(&aio_fs);
diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index c2b8663f5b00..89714308c25b 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -20,6 +20,7 @@
 #include <linux/kernel.h>
 #include <linux/magic.h>
 #include <linux/anon_inodes.h>
+#include <linux/pseudo_fs.h>
 
 #include <linux/uaccess.h>
 
@@ -39,16 +40,18 @@ static const struct dentry_operations anon_inodefs_dentry_operations = {
 	.d_dname	= anon_inodefs_dname,
 };
 
-static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type,
-				int flags, const char *dev_name, void *data)
+static int anon_inodefs_init_fs_context(struct fs_context *fc)
 {
-	return mount_pseudo(fs_type, "anon_inode:", NULL,
-			&anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
+	struct pseudo_fs_context *ctx = init_pseudo(fc, ANON_INODE_FS_MAGIC);
+	if (!ctx)
+		return -ENOMEM;
+	ctx->dops = &anon_inodefs_dentry_operations;
+	return 0;
 }
 
 static struct file_system_type anon_inode_fs_type = {
 	.name		= "anon_inodefs",
-	.mount		= anon_inodefs_mount,
+	.init_fs_context = anon_inodefs_init_fs_context,
 	.kill_sb	= kill_anon_super,
 };
 
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index b8e145552ec7..cdb45829354d 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -23,6 +23,7 @@
 #include <linux/pagemap.h>
 #include <linux/namei.h>
 #include <linux/mount.h>
+#include <linux/fs_context.h>
 #include <linux/syscalls.h>
 #include <linux/fs.h>
 #include <linux/uaccess.h>
@@ -821,7 +822,7 @@ static const struct super_operations s_ops = {
 	.evict_inode	= bm_evict_inode,
 };
 
-static int bm_fill_super(struct super_block *sb, void *data, int silent)
+static int bm_fill_super(struct super_block *sb, struct fs_context *fc)
 {
 	int err;
 	static const struct tree_descr bm_files[] = {
@@ -836,10 +837,19 @@ static int bm_fill_super(struct super_block *sb, void *data, int silent)
 	return err;
 }
 
-static struct dentry *bm_mount(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *data)
+static int bm_get_tree(struct fs_context *fc)
 {
-	return mount_single(fs_type, flags, data, bm_fill_super);
+	return get_tree_single(fc, bm_fill_super);
+}
+
+static const struct fs_context_operations bm_context_ops = {
+	.get_tree	= bm_get_tree,
+};
+
+static int bm_init_fs_context(struct fs_context *fc)
+{
+	fc->ops = &bm_context_ops;
+	return 0;
 }
 
 static struct linux_binfmt misc_format = {
@@ -850,7 +860,7 @@ static struct linux_binfmt misc_format = {
 static struct file_system_type bm_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "binfmt_misc",
-	.mount		= bm_mount,
+	.init_fs_context = bm_init_fs_context,
 	.kill_sb	= kill_litter_super,
 };
 MODULE_ALIAS_FS("binfmt_misc");
diff --git a/fs/block_dev.c b/fs/block_dev.c
index f00b569a9f89..4707dfff991b 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -26,6 +26,7 @@
 #include <linux/writeback.h>
 #include <linux/mpage.h>
 #include <linux/mount.h>
+#include <linux/pseudo_fs.h>
 #include <linux/uio.h>
 #include <linux/namei.h>
 #include <linux/log2.h>
@@ -821,19 +822,19 @@ static const struct super_operations bdev_sops = {
 	.evict_inode = bdev_evict_inode,
 };
 
-static struct dentry *bd_mount(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *data)
+static int bd_init_fs_context(struct fs_context *fc)
 {
-	struct dentry *dent;
-	dent = mount_pseudo(fs_type, "bdev:", &bdev_sops, NULL, BDEVFS_MAGIC);
-	if (!IS_ERR(dent))
-		dent->d_sb->s_iflags |= SB_I_CGROUPWB;
-	return dent;
+	struct pseudo_fs_context *ctx = init_pseudo(fc, BDEVFS_MAGIC);
+	if (!ctx)
+		return -ENOMEM;
+	fc->s_iflags |= SB_I_CGROUPWB;
+	ctx->ops = &bdev_sops;
+	return 0;
 }
 
 static struct file_system_type bd_type = {
 	.name		= "bdev",
-	.mount		= bd_mount,
+	.init_fs_context = bd_init_fs_context,
 	.kill_sb	= kill_anon_super,
 };
 
diff --git a/fs/btrfs/tests/btrfs-tests.c b/fs/btrfs/tests/btrfs-tests.c
index 9238fd4f1734..1e3ba4949399 100644
--- a/fs/btrfs/tests/btrfs-tests.c
+++ b/fs/btrfs/tests/btrfs-tests.c
@@ -5,6 +5,7 @@
 
 #include <linux/fs.h>
 #include <linux/mount.h>
+#include <linux/pseudo_fs.h>
 #include <linux/magic.h>
 #include "btrfs-tests.h"
 #include "../ctree.h"
@@ -32,17 +33,19 @@ static const struct super_operations btrfs_test_super_ops = {
 	.destroy_inode	= btrfs_test_destroy_inode,
 };
 
-static struct dentry *btrfs_test_mount(struct file_system_type *fs_type,
-				       int flags, const char *dev_name,
-				       void *data)
+
+static int btrfs_test_init_fs_context(struct fs_context *fc)
 {
-	return mount_pseudo(fs_type, "btrfs_test:", &btrfs_test_super_ops,
-			    NULL, BTRFS_TEST_MAGIC);
+	struct pseudo_fs_context *ctx = init_pseudo(fc, BTRFS_TEST_MAGIC);
+	if (!ctx)
+		return -ENOMEM;
+	ctx->ops = &btrfs_test_super_ops;
+	return 0;
 }
 
 static struct file_system_type test_type = {
 	.name		= "btrfs_test_fs",
-	.mount		= btrfs_test_mount,
+	.init_fs_context = btrfs_test_init_fs_context,
 	.kill_sb	= kill_anon_super,
 };
 
diff --git a/fs/configfs/mount.c b/fs/configfs/mount.c
index 791304fdde9d..55438dd58189 100644
--- a/fs/configfs/mount.c
+++ b/fs/configfs/mount.c
@@ -13,6 +13,7 @@
 #include <linux/fs.h>
 #include <linux/module.h>
 #include <linux/mount.h>
+#include <linux/fs_context.h>
 #include <linux/pagemap.h>
 #include <linux/init.h>
 #include <linux/slab.h>
@@ -52,7 +53,7 @@ static struct configfs_dirent configfs_root = {
 	.s_iattr	= NULL,
 };
 
-static int configfs_fill_super(struct super_block *sb, void *data, int silent)
+static int configfs_fill_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct inode *inode;
 	struct dentry *root;
@@ -88,16 +89,25 @@ static int configfs_fill_super(struct super_block *sb, void *data, int silent)
 	return 0;
 }
 
-static struct dentry *configfs_do_mount(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *data)
+static int configfs_get_tree(struct fs_context *fc)
 {
-	return mount_single(fs_type, flags, data, configfs_fill_super);
+	return get_tree_single(fc, configfs_fill_super);
+}
+
+static const struct fs_context_operations configfs_context_ops = {
+	.get_tree	= configfs_get_tree,
+};
+
+static int configfs_init_fs_context(struct fs_context *fc)
+{
+	fc->ops = &configfs_context_ops;
+	return 0;
 }
 
 static struct file_system_type configfs_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "configfs",
-	.mount		= configfs_do_mount,
+	.init_fs_context = configfs_init_fs_context,
 	.kill_sb	= kill_litter_super,
 };
 MODULE_ALIAS_FS("configfs");
diff --git a/fs/d_path.c b/fs/d_path.c
index e8fce6b1174f..a7d0a96b35ce 100644
--- a/fs/d_path.c
+++ b/fs/d_path.c
@@ -316,7 +316,6 @@ char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
 		end = ERR_PTR(-ENAMETOOLONG);
 	return end;
 }
-EXPORT_SYMBOL(simple_dname);
 
 /*
  * Write full pathname from the root of the filesystem into the buffer.
diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
index 5bc3c4a4c563..fa4f6447ddad 100644
--- a/fs/efivarfs/super.c
+++ b/fs/efivarfs/super.c
@@ -7,6 +7,7 @@
 #include <linux/ctype.h>
 #include <linux/efi.h>
 #include <linux/fs.h>
+#include <linux/fs_context.h>
 #include <linux/module.h>
 #include <linux/pagemap.h>
 #include <linux/ucs2_string.h>
@@ -28,8 +29,6 @@ static const struct super_operations efivarfs_ops = {
 	.evict_inode = efivarfs_evict_inode,
 };
 
-static struct super_block *efivarfs_sb;
-
 /*
  * Compare two efivarfs file names.
  *
@@ -188,14 +187,12 @@ static int efivarfs_destroy(struct efivar_entry *entry, void *data)
 	return 0;
 }
 
-static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
+static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct inode *inode = NULL;
 	struct dentry *root;
 	int err;
 
-	efivarfs_sb = sb;
-
 	sb->s_maxbytes          = MAX_LFS_FILESIZE;
 	sb->s_blocksize         = PAGE_SIZE;
 	sb->s_blocksize_bits    = PAGE_SHIFT;
@@ -223,16 +220,24 @@ static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
 	return err;
 }
 
-static struct dentry *efivarfs_mount(struct file_system_type *fs_type,
-				    int flags, const char *dev_name, void *data)
+static int efivarfs_get_tree(struct fs_context *fc)
+{
+	return get_tree_single(fc, efivarfs_fill_super);
+}
+
+static const struct fs_context_operations efivarfs_context_ops = {
+	.get_tree	= efivarfs_get_tree,
+};
+
+static int efivarfs_init_fs_context(struct fs_context *fc)
 {
-	return mount_single(fs_type, flags, data, efivarfs_fill_super);
+	fc->ops = &efivarfs_context_ops;
+	return 0;
 }
 
 static void efivarfs_kill_sb(struct super_block *sb)
 {
 	kill_litter_super(sb);
-	efivarfs_sb = NULL;
 
 	/* Remove all entries and destroy */
 	__efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
@@ -241,7 +246,7 @@ static void efivarfs_kill_sb(struct super_block *sb)
 static struct file_system_type efivarfs_type = {
 	.owner   = THIS_MODULE,
 	.name    = "efivarfs",
-	.mount   = efivarfs_mount,
+	.init_fs_context = efivarfs_init_fs_context,
 	.kill_sb = efivarfs_kill_sb,
 };
 
diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index 0d388faa25d1..460ea4206fa2 100644
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -264,6 +264,7 @@ int fs_lookup_param(struct fs_context *fc,
 		return invalf(fc, "%s: not usable as path", param->key);
 	}
 
+	f->refcnt++; /* filename_lookup() drops our ref. */
 	ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
 	if (ret < 0) {
 		errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);
diff --git a/fs/fsopen.c b/fs/fsopen.c
index a8bf83ce8d4e..043ffa8dc263 100644
--- a/fs/fsopen.c
+++ b/fs/fsopen.c
@@ -226,6 +226,8 @@ static int vfs_fsconfig_locked(struct fs_context *fc, int cmd,
 	case FSCONFIG_CMD_CREATE:
 		if (fc->phase != FS_CONTEXT_CREATE_PARAMS)
 			return -EBUSY;
+		if (!mount_capable(fc))
+			return -EPERM;
 		fc->phase = FS_CONTEXT_CREATING;
 		ret = vfs_get_tree(fc);
 		if (ret)
diff --git a/fs/fuse/control.c b/fs/fuse/control.c
index 14ce1e47f980..c23f6f243ad4 100644
--- a/fs/fuse/control.c
+++ b/fs/fuse/control.c
@@ -346,7 +346,7 @@ static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fctx)
 
 static int fuse_ctl_get_tree(struct fs_context *fc)
 {
-	return vfs_get_super(fc, vfs_get_single_super, fuse_ctl_fill_super);
+	return get_tree_single(fc, fuse_ctl_fill_super);
 }
 
 static const struct fs_context_operations fuse_ctl_context_ops = {
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 1dcc57189382..a478df035651 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -1299,7 +1299,7 @@ static int hugetlbfs_get_tree(struct fs_context *fc)
 	int err = hugetlbfs_validate(fc);
 	if (err)
 		return err;
-	return vfs_get_super(fc, vfs_get_independent_super, hugetlbfs_fill_super);
+	return get_tree_nodev(fc, hugetlbfs_fill_super);
 }
 
 static void hugetlbfs_fs_context_free(struct fs_context *fc)
diff --git a/fs/internal.h b/fs/internal.h
index 2f3c3de51fad..b9bad2d30cef 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -14,6 +14,7 @@ struct path;
 struct mount;
 struct shrink_control;
 struct fs_context;
+struct user_namespace;
 
 /*
  * block_dev.c
@@ -107,6 +108,7 @@ extern struct file *alloc_empty_file_noaccount(int, const struct cred *);
 extern int reconfigure_super(struct fs_context *);
 extern bool trylock_super(struct super_block *sb);
 extern struct super_block *user_get_super(dev_t);
+extern bool mount_capable(struct fs_context *);
 
 /*
  * open.c
@@ -154,6 +156,7 @@ extern int d_set_mounted(struct dentry *dentry);
 extern long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc);
 extern struct dentry *d_alloc_cursor(struct dentry *);
 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
+extern char *simple_dname(struct dentry *, char *, int);
 
 /*
  * read_write.c
diff --git a/fs/libfs.c b/fs/libfs.c
index 7e52e77692ec..c9b2850c0f7c 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -17,6 +17,8 @@
 #include <linux/exportfs.h>
 #include <linux/writeback.h>
 #include <linux/buffer_head.h> /* sync_mapping_buffers */
+#include <linux/fs_context.h>
+#include <linux/pseudo_fs.h>
 
 #include <linux/uaccess.h>
 
@@ -236,34 +238,22 @@ static const struct super_operations simple_super_operations = {
 	.statfs		= simple_statfs,
 };
 
-/*
- * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
- * will never be mountable)
- */
-struct dentry *mount_pseudo_xattr(struct file_system_type *fs_type, char *name,
-	const struct super_operations *ops, const struct xattr_handler **xattr,
-	const struct dentry_operations *dops, unsigned long magic)
+static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
 {
-	struct super_block *s;
-	struct dentry *dentry;
+	struct pseudo_fs_context *ctx = fc->fs_private;
 	struct inode *root;
-	struct qstr d_name = QSTR_INIT(name, strlen(name));
-
-	s = sget_userns(fs_type, NULL, set_anon_super, SB_KERNMOUNT|SB_NOUSER,
-			&init_user_ns, NULL);
-	if (IS_ERR(s))
-		return ERR_CAST(s);
 
 	s->s_maxbytes = MAX_LFS_FILESIZE;
 	s->s_blocksize = PAGE_SIZE;
 	s->s_blocksize_bits = PAGE_SHIFT;
-	s->s_magic = magic;
-	s->s_op = ops ? ops : &simple_super_operations;
-	s->s_xattr = xattr;
+	s->s_magic = ctx->magic;
+	s->s_op = ctx->ops ?: &simple_super_operations;
+	s->s_xattr = ctx->xattr;
 	s->s_time_gran = 1;
 	root = new_inode(s);
 	if (!root)
-		goto Enomem;
+		return -ENOMEM;
+
 	/*
 	 * since this is the first inode, make it number 1. New inodes created
 	 * after this must take care not to collide with it (by passing
@@ -272,22 +262,48 @@ struct dentry *mount_pseudo_xattr(struct file_system_type *fs_type, char *name,
 	root->i_ino = 1;
 	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
 	root->i_atime = root->i_mtime = root->i_ctime = current_time(root);
-	dentry = __d_alloc(s, &d_name);
-	if (!dentry) {
-		iput(root);
-		goto Enomem;
+	s->s_root = d_make_root(root);
+	if (!s->s_root)
+		return -ENOMEM;
+	s->s_d_op = ctx->dops;
+	return 0;
+}
+
+static int pseudo_fs_get_tree(struct fs_context *fc)
+{
+	return get_tree_nodev(fc, pseudo_fs_fill_super);
+}
+
+static void pseudo_fs_free(struct fs_context *fc)
+{
+	kfree(fc->fs_private);
+}
+
+static const struct fs_context_operations pseudo_fs_context_ops = {
+	.free		= pseudo_fs_free,
+	.get_tree	= pseudo_fs_get_tree,
+};
+
+/*
+ * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
+ * will never be mountable)
+ */
+struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
+					unsigned long magic)
+{
+	struct pseudo_fs_context *ctx;
+
+	ctx = kzalloc(sizeof(struct pseudo_fs_context), GFP_KERNEL);
+	if (likely(ctx)) {
+		ctx->magic = magic;
+		fc->fs_private = ctx;
+		fc->ops = &pseudo_fs_context_ops;
+		fc->sb_flags |= SB_NOUSER;
+		fc->global = true;
 	}
-	d_instantiate(dentry, root);
-	s->s_root = dentry;
-	s->s_d_op = dops;
-	s->s_flags |= SB_ACTIVE;
-	return dget(s->s_root);
-
-Enomem:
-	deactivate_locked_super(s);
-	return ERR_PTR(-ENOMEM);
+	return ctx;
 }
-EXPORT_SYMBOL(mount_pseudo_xattr);
+EXPORT_SYMBOL(init_pseudo);
 
 int simple_open(struct inode *inode, struct file *file)
 {
diff --git a/fs/namespace.c b/fs/namespace.c
index 6fbc9126367a..f0d664adb9ba 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -29,6 +29,7 @@
 #include <linux/sched/task.h>
 #include <uapi/linux/mount.h>
 #include <linux/fs_context.h>
+#include <linux/shmem_fs.h>
 
 #include "pnode.h"
 #include "internal.h"
@@ -2788,6 +2789,8 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
 		err = vfs_parse_fs_string(fc, "source", name, strlen(name));
 	if (!err)
 		err = parse_monolithic_mount_data(fc, data);
+	if (!err && !mount_capable(fc))
+		err = -EPERM;
 	if (!err)
 		err = vfs_get_tree(fc);
 	if (!err)
@@ -3295,8 +3298,8 @@ struct dentry *mount_subtree(struct vfsmount *m, const char *name)
 }
 EXPORT_SYMBOL(mount_subtree);
 
-int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type,
-	       unsigned long flags, void __user *data)
+int ksys_mount(const char __user *dev_name, const char __user *dir_name,
+	       const char __user *type, unsigned long flags, void __user *data)
 {
 	int ret;
 	char *kernel_type;
@@ -3687,13 +3690,8 @@ static void __init init_mount_tree(void)
 	struct mount *m;
 	struct mnt_namespace *ns;
 	struct path root;
-	struct file_system_type *type;
 
-	type = get_fs_type("rootfs");
-	if (!type)
-		panic("Can't find rootfs type");
-	mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
-	put_filesystem(type);
+	mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
 	if (IS_ERR(mnt))
 		panic("Can't create rootfs");
 
@@ -3746,6 +3744,7 @@ void __init mnt_init(void)
 	fs_kobj = kobject_create_and_add("fs", NULL);
 	if (!fs_kobj)
 		printk(KERN_WARNING "%s: kobj create error\n", __func__);
+	shmem_init();
 	init_rootfs();
 	init_mount_tree();
 }
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 0a9a49ded546..13c548733860 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -8,6 +8,7 @@
 #include <linux/slab.h>
 #include <linux/namei.h>
 #include <linux/ctype.h>
+#include <linux/fs_context.h>
 
 #include <linux/sunrpc/svcsock.h>
 #include <linux/lockd/lockd.h>
@@ -1337,7 +1338,7 @@ void nfsd_client_rmdir(struct dentry *dentry)
 	inode_unlock(dir);
 }
 
-static int nfsd_fill_super(struct super_block * sb, void * data, int silent)
+static int nfsd_fill_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct nfsd_net *nn = net_generic(current->nsproxy->net_ns,
 							nfsd_net_id);
@@ -1372,7 +1373,7 @@ static int nfsd_fill_super(struct super_block * sb, void * data, int silent)
 #endif
 		/* last one */ {""}
 	};
-	get_net(sb->s_fs_info);
+
 	ret = simple_fill_super(sb, 0x6e667364, nfsd_files);
 	if (ret)
 		return ret;
@@ -1381,14 +1382,31 @@ static int nfsd_fill_super(struct super_block * sb, void * data, int silent)
 		return PTR_ERR(dentry);
 	nn->nfsd_client_dir = dentry;
 	return 0;
+}
 
+static int nfsd_fs_get_tree(struct fs_context *fc)
+{
+	fc->s_fs_info = get_net(fc->net_ns);
+	return vfs_get_super(fc, vfs_get_keyed_super, nfsd_fill_super);
 }
 
-static struct dentry *nfsd_mount(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *data)
+static void nfsd_fs_free_fc(struct fs_context *fc)
 {
-	struct net *net = current->nsproxy->net_ns;
-	return mount_ns(fs_type, flags, data, net, net->user_ns, nfsd_fill_super);
+	if (fc->s_fs_info)
+		put_net(fc->s_fs_info);
+}
+
+static const struct fs_context_operations nfsd_fs_context_ops = {
+	.free		= nfsd_fs_free_fc,
+	.get_tree	= nfsd_fs_get_tree,
+};
+
+static int nfsd_init_fs_context(struct fs_context *fc)
+{
+	put_user_ns(fc->user_ns);
+	fc->user_ns = get_user_ns(fc->net_ns->user_ns);
+	fc->ops = &nfsd_fs_context_ops;
+	return 0;
 }
 
 static void nfsd_umount(struct super_block *sb)
@@ -1402,7 +1420,7 @@ static void nfsd_umount(struct super_block *sb)
 static struct file_system_type nfsd_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "nfsd",
-	.mount		= nfsd_mount,
+	.init_fs_context = nfsd_init_fs_context,
 	.kill_sb	= nfsd_umount,
 };
 MODULE_ALIAS_FS("nfsd");
diff --git a/fs/nsfs.c b/fs/nsfs.c
index e3bf08c5af41..a0431642c6b5 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/mount.h>
+#include <linux/pseudo_fs.h>
 #include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/proc_ns.h>
@@ -258,15 +259,20 @@ static const struct super_operations nsfs_ops = {
 	.evict_inode = nsfs_evict,
 	.show_path = nsfs_show_path,
 };
-static struct dentry *nsfs_mount(struct file_system_type *fs_type,
-			int flags, const char *dev_name, void *data)
+
+static int nsfs_init_fs_context(struct fs_context *fc)
 {
-	return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
-			&ns_dentry_operations, NSFS_MAGIC);
+	struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC);
+	if (!ctx)
+		return -ENOMEM;
+	ctx->ops = &nsfs_ops;
+	ctx->dops = &ns_dentry_operations;
+	return 0;
 }
+
 static struct file_system_type nsfs = {
 	.name = "nsfs",
-	.mount = nsfs_mount,
+	.init_fs_context = nsfs_init_fs_context,
 	.kill_sb = kill_anon_super,
 };
 
diff --git a/fs/openpromfs/inode.c b/fs/openpromfs/inode.c
index e6cb7689fec4..40c8c2e32fa3 100644
--- a/fs/openpromfs/inode.c
+++ b/fs/openpromfs/inode.c
@@ -9,6 +9,7 @@
 #include <linux/types.h>
 #include <linux/string.h>
 #include <linux/fs.h>
+#include <linux/fs_context.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/seq_file.h>
@@ -375,7 +376,7 @@ static const struct super_operations openprom_sops = {
 	.remount_fs	= openprom_remount,
 };
 
-static int openprom_fill_super(struct super_block *s, void *data, int silent)
+static int openprom_fill_super(struct super_block *s, struct fs_context *fc)
 {
 	struct inode *root_inode;
 	struct op_inode_info *oi;
@@ -409,16 +410,25 @@ out_no_root:
 	return ret;
 }
 
-static struct dentry *openprom_mount(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *data)
+static int openpromfs_get_tree(struct fs_context *fc)
 {
-	return mount_single(fs_type, flags, data, openprom_fill_super);
+	return get_tree_single(fc, openprom_fill_super);
+}
+
+static const struct fs_context_operations openpromfs_context_ops = {
+	.get_tree	= openpromfs_get_tree,
+};
+
+static int openpromfs_init_fs_context(struct fs_context *fc)
+{
+	fc->ops = &openpromfs_context_ops;
+	return 0;
 }
 
 static struct file_system_type openprom_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "openpromfs",
-	.mount		= openprom_mount,
+	.init_fs_context = openpromfs_init_fs_context,
 	.kill_sb	= kill_anon_super,
 };
 MODULE_ALIAS_FS("openpromfs");
diff --git a/fs/pipe.c b/fs/pipe.c
index 41065901106b..8a2ab2f974bd 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -14,6 +14,7 @@
 #include <linux/fs.h>
 #include <linux/log2.h>
 #include <linux/mount.h>
+#include <linux/pseudo_fs.h>
 #include <linux/magic.h>
 #include <linux/pipe_fs_i.h>
 #include <linux/uio.h>
@@ -1182,16 +1183,20 @@ static const struct super_operations pipefs_ops = {
  * any operations on the root directory. However, we need a non-trivial
  * d_name - pipe: will go nicely and kill the special-casing in procfs.
  */
-static struct dentry *pipefs_mount(struct file_system_type *fs_type,
-			 int flags, const char *dev_name, void *data)
+
+static int pipefs_init_fs_context(struct fs_context *fc)
 {
-	return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
-			&pipefs_dentry_operations, PIPEFS_MAGIC);
+	struct pseudo_fs_context *ctx = init_pseudo(fc, PIPEFS_MAGIC);
+	if (!ctx)
+		return -ENOMEM;
+	ctx->ops = &pipefs_ops;
+	ctx->dops = &pipefs_dentry_operations;
+	return 0;
 }
 
 static struct file_system_type pipe_fs_type = {
 	.name		= "pipefs",
-	.mount		= pipefs_mount,
+	.init_fs_context = pipefs_init_fs_context,
 	.kill_sb	= kill_anon_super,
 };
 
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 522199e9525e..33f72d1b92cc 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -157,8 +157,6 @@ static int proc_get_tree(struct fs_context *fc)
 {
 	struct proc_fs_context *ctx = fc->fs_private;
 
-	put_user_ns(fc->user_ns);
-	fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);
 	fc->s_fs_info = ctx->pid_ns;
 	return vfs_get_super(fc, vfs_get_keyed_super, proc_fill_super);
 }
@@ -167,8 +165,7 @@ static void proc_fs_context_free(struct fs_context *fc)
 {
 	struct proc_fs_context *ctx = fc->fs_private;
 
-	if (ctx->pid_ns)
-		put_pid_ns(ctx->pid_ns);
+	put_pid_ns(ctx->pid_ns);
 	kfree(ctx);
 }
 
@@ -188,6 +185,8 @@ static int proc_init_fs_context(struct fs_context *fc)
 		return -ENOMEM;
 
 	ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));
+	put_user_ns(fc->user_ns);
+	fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);
 	fc->fs_private = ctx;
 	fc->ops = &proc_fs_context_ops;
 	return 0;
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index 11201b2d06b9..733c6b4193dc 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -266,12 +266,8 @@ static struct file_system_type ramfs_fs_type = {
 	.fs_flags	= FS_USERNS_MOUNT,
 };
 
-int __init init_ramfs_fs(void)
+static int __init init_ramfs_fs(void)
 {
-	static unsigned long once;
-
-	if (test_and_set_bit(0, &once))
-		return 0;
 	return register_filesystem(&ramfs_fs_type);
 }
 fs_initcall(init_ramfs_fs);
diff --git a/fs/super.c b/fs/super.c
index 2739f57515f8..113c58f19425 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -476,6 +476,17 @@ void generic_shutdown_super(struct super_block *sb)
 
 EXPORT_SYMBOL(generic_shutdown_super);
 
+bool mount_capable(struct fs_context *fc)
+{
+	struct user_namespace *user_ns = fc->global ? &init_user_ns
+						    : fc->user_ns;
+
+	if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
+		return capable(CAP_SYS_ADMIN);
+	else
+		return ns_capable(user_ns, CAP_SYS_ADMIN);
+}
+
 /**
  * sget_fc - Find or create a superblock
  * @fc:	Filesystem context.
@@ -503,20 +514,6 @@ struct super_block *sget_fc(struct fs_context *fc,
 	struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
 	int err;
 
-	if (!(fc->sb_flags & SB_KERNMOUNT) &&
-	    fc->purpose != FS_CONTEXT_FOR_SUBMOUNT) {
-		/* Don't allow mounting unless the caller has CAP_SYS_ADMIN
-		 * over the namespace.
-		 */
-		if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT)) {
-			if (!capable(CAP_SYS_ADMIN))
-				return ERR_PTR(-EPERM);
-		} else {
-			if (!ns_capable(fc->user_ns, CAP_SYS_ADMIN))
-				return ERR_PTR(-EPERM);
-		}
-	}
-
 retry:
 	spin_lock(&sb_lock);
 	if (test) {
@@ -543,6 +540,7 @@ retry:
 	}
 	fc->s_fs_info = NULL;
 	s->s_type = fc->fs_type;
+	s->s_iflags |= fc->s_iflags;
 	strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id));
 	list_add_tail(&s->s_list, &super_blocks);
 	hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
@@ -565,28 +563,31 @@ share_extant_sb:
 EXPORT_SYMBOL(sget_fc);
 
 /**
- *	sget_userns -	find or create a superblock
- *	@type:	filesystem type superblock should belong to
- *	@test:	comparison callback
- *	@set:	setup callback
- *	@flags:	mount flags
- *	@user_ns: User namespace for the super_block
- *	@data:	argument to each of them
+ *	sget	-	find or create a superblock
+ *	@type:	  filesystem type superblock should belong to
+ *	@test:	  comparison callback
+ *	@set:	  setup callback
+ *	@flags:	  mount flags
+ *	@data:	  argument to each of them
  */
-struct super_block *sget_userns(struct file_system_type *type,
+struct super_block *sget(struct file_system_type *type,
 			int (*test)(struct super_block *,void *),
 			int (*set)(struct super_block *,void *),
-			int flags, struct user_namespace *user_ns,
+			int flags,
 			void *data)
 {
+	struct user_namespace *user_ns = current_user_ns();
 	struct super_block *s = NULL;
 	struct super_block *old;
 	int err;
 
-	if (!(flags & (SB_KERNMOUNT|SB_SUBMOUNT)) &&
-	    !(type->fs_flags & FS_USERNS_MOUNT) &&
-	    !capable(CAP_SYS_ADMIN))
-		return ERR_PTR(-EPERM);
+	/* We don't yet pass the user namespace of the parent
+	 * mount through to here so always use &init_user_ns
+	 * until that changes.
+	 */
+	if (flags & SB_SUBMOUNT)
+		user_ns = &init_user_ns;
+
 retry:
 	spin_lock(&sb_lock);
 	if (test) {
@@ -627,39 +628,6 @@ retry:
 	register_shrinker_prepared(&s->s_shrink);
 	return s;
 }
-
-EXPORT_SYMBOL(sget_userns);
-
-/**
- *	sget	-	find or create a superblock
- *	@type:	  filesystem type superblock should belong to
- *	@test:	  comparison callback
- *	@set:	  setup callback
- *	@flags:	  mount flags
- *	@data:	  argument to each of them
- */
-struct super_block *sget(struct file_system_type *type,
-			int (*test)(struct super_block *,void *),
-			int (*set)(struct super_block *,void *),
-			int flags,
-			void *data)
-{
-	struct user_namespace *user_ns = current_user_ns();
-
-	/* We don't yet pass the user namespace of the parent
-	 * mount through to here so always use &init_user_ns
-	 * until that changes.
-	 */
-	if (flags & SB_SUBMOUNT)
-		user_ns = &init_user_ns;
-
-	/* Ensure the requestor has permissions over the target filesystem */
-	if (!(flags & (SB_KERNMOUNT|SB_SUBMOUNT)) && !ns_capable(user_ns, CAP_SYS_ADMIN))
-		return ERR_PTR(-EPERM);
-
-	return sget_userns(type, test, set, flags, user_ns, data);
-}
-
 EXPORT_SYMBOL(sget);
 
 void drop_super(struct super_block *sb)
@@ -1147,50 +1115,6 @@ void kill_litter_super(struct super_block *sb)
 }
 EXPORT_SYMBOL(kill_litter_super);
 
-static int ns_test_super(struct super_block *sb, void *data)
-{
-	return sb->s_fs_info == data;
-}
-
-static int ns_set_super(struct super_block *sb, void *data)
-{
-	sb->s_fs_info = data;
-	return set_anon_super(sb, NULL);
-}
-
-struct dentry *mount_ns(struct file_system_type *fs_type,
-	int flags, void *data, void *ns, struct user_namespace *user_ns,
-	int (*fill_super)(struct super_block *, void *, int))
-{
-	struct super_block *sb;
-
-	/* Don't allow mounting unless the caller has CAP_SYS_ADMIN
-	 * over the namespace.
-	 */
-	if (!(flags & SB_KERNMOUNT) && !ns_capable(user_ns, CAP_SYS_ADMIN))
-		return ERR_PTR(-EPERM);
-
-	sb = sget_userns(fs_type, ns_test_super, ns_set_super, flags,
-			 user_ns, ns);
-	if (IS_ERR(sb))
-		return ERR_CAST(sb);
-
-	if (!sb->s_root) {
-		int err;
-		err = fill_super(sb, data, flags & SB_SILENT ? 1 : 0);
-		if (err) {
-			deactivate_locked_super(sb);
-			return ERR_PTR(err);
-		}
-
-		sb->s_flags |= SB_ACTIVE;
-	}
-
-	return dget(sb->s_root);
-}
-
-EXPORT_SYMBOL(mount_ns);
-
 int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
 {
 	return set_anon_super(sb, NULL);
@@ -1274,6 +1198,22 @@ int vfs_get_super(struct fs_context *fc,
 }
 EXPORT_SYMBOL(vfs_get_super);
 
+int get_tree_nodev(struct fs_context *fc,
+		  int (*fill_super)(struct super_block *sb,
+				    struct fs_context *fc))
+{
+	return vfs_get_super(fc, vfs_get_independent_super, fill_super);
+}
+EXPORT_SYMBOL(get_tree_nodev);
+
+int get_tree_single(struct fs_context *fc,
+		  int (*fill_super)(struct super_block *sb,
+				    struct fs_context *fc))
+{
+	return vfs_get_super(fc, vfs_get_single_super, fill_super);
+}
+EXPORT_SYMBOL(get_tree_single);
+
 #ifdef CONFIG_BLOCK
 static int set_bdev_super(struct super_block *s, void *data)
 {
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 1b56686ab178..db81cfbab9d6 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -72,8 +72,7 @@ static int sysfs_init_fs_context(struct fs_context *fc)
 	fc->fs_private = kfc;
 	fc->ops = &sysfs_fs_context_ops;
 	if (netns) {
-		if (fc->user_ns)
-			put_user_ns(fc->user_ns);
+		put_user_ns(fc->user_ns);
 		fc->user_ns = get_user_ns(netns->user_ns);
 	}
 	fc->global = true;