vfs: split off vfsmount-related parts of vfs_kern_mount()

new function: mount_fs().  Does all work done by vfs_kern_mount()
except the allocation and filling of vfsmount; returns root dentry
or ERR_PTR().

vfs_kern_mount() switched to using it and taken to fs/namespace.c,
along with its wrappers.

alloc_vfsmnt()/free_vfsmnt() made static.

functions in namespace.c slightly reordered.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/internal.h

@@ -12,6 +12,7 @@
 #include <linux/lglock.h>
 
 struct super_block;
+struct file_system_type;
 struct linux_binprm;
 struct path;
 
@@ -61,8 +62,6 @@ extern int check_unsafe_exec(struct linux_binprm *);
 extern int copy_mount_options(const void __user *, unsigned long *);
 extern int copy_mount_string(const void __user *, char **);
 
-extern void free_vfsmnt(struct vfsmount *);
-extern struct vfsmount *alloc_vfsmnt(const char *);
 extern unsigned int mnt_get_count(struct vfsmount *mnt);
 extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
 extern void mnt_set_mountpoint(struct vfsmount *, struct dentry *,
@@ -99,6 +98,8 @@ extern struct file *get_empty_filp(void);
 extern int do_remount_sb(struct super_block *, int, void *, int);
 extern void __put_super(struct super_block *sb);
 extern void put_super(struct super_block *sb);
+extern struct dentry *mount_fs(struct file_system_type *,
+			       int, const char *, void *);
 
 /*
  * open.c

fs/namespace.c

@@ -196,7 +196,7 @@ unsigned int mnt_get_count(struct vfsmount *mnt)
 #endif
 }
 
-struct vfsmount *alloc_vfsmnt(const char *name)
+static struct vfsmount *alloc_vfsmnt(const char *name)
 {
 	struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
 	if (mnt) {
@@ -466,7 +466,7 @@ static void __mnt_unmake_readonly(struct vfsmount *mnt)
 	br_write_unlock(vfsmount_lock);
 }
 
-void free_vfsmnt(struct vfsmount *mnt)
+static void free_vfsmnt(struct vfsmount *mnt)
 {
 	kfree(mnt->mnt_devname);
 	mnt_free_id(mnt);
@@ -670,6 +670,36 @@ static struct vfsmount *skip_mnt_tree(struct vfsmount *p)
 	return p;
 }
 
+struct vfsmount *
+vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
+{
+	struct vfsmount *mnt;
+	struct dentry *root;
+
+	if (!type)
+		return ERR_PTR(-ENODEV);
+
+	mnt = alloc_vfsmnt(name);
+	if (!mnt)
+		return ERR_PTR(-ENOMEM);
+
+	if (flags & MS_KERNMOUNT)
+		mnt->mnt_flags = MNT_INTERNAL;
+
+	root = mount_fs(type, flags, name, data);
+	if (IS_ERR(root)) {
+		free_vfsmnt(mnt);
+		return ERR_CAST(root);
+	}
+
+	mnt->mnt_root = root;
+	mnt->mnt_sb = root->d_sb;
+	mnt->mnt_mountpoint = mnt->mnt_root;
+	mnt->mnt_parent = mnt;
+	return mnt;
+}
+EXPORT_SYMBOL_GPL(vfs_kern_mount);
+
 static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
 					int flag)
 {
@@ -1905,7 +1935,81 @@ out:
 	return err;
 }
 
-static int do_add_mount(struct vfsmount *, struct path *, int);
+static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
+{
+	int err;
+	const char *subtype = strchr(fstype, '.');
+	if (subtype) {
+		subtype++;
+		err = -EINVAL;
+		if (!subtype[0])
+			goto err;
+	} else
+		subtype = "";
+
+	mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
+	err = -ENOMEM;
+	if (!mnt->mnt_sb->s_subtype)
+		goto err;
+	return mnt;
+
+ err:
+	mntput(mnt);
+	return ERR_PTR(err);
+}
+
+struct vfsmount *
+do_kern_mount(const char *fstype, int flags, const char *name, void *data)
+{
+	struct file_system_type *type = get_fs_type(fstype);
+	struct vfsmount *mnt;
+	if (!type)
+		return ERR_PTR(-ENODEV);
+	mnt = vfs_kern_mount(type, flags, name, data);
+	if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
+	    !mnt->mnt_sb->s_subtype)
+		mnt = fs_set_subtype(mnt, fstype);
+	put_filesystem(type);
+	return mnt;
+}
+EXPORT_SYMBOL_GPL(do_kern_mount);
+
+/*
+ * add a mount into a namespace's mount tree
+ */
+static int do_add_mount(struct vfsmount *newmnt, struct path *path, int mnt_flags)
+{
+	int err;
+
+	mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
+
+	down_write(&namespace_sem);
+	/* Something was mounted here while we slept */
+	err = follow_down(path, true);
+	if (err < 0)
+		goto unlock;
+
+	err = -EINVAL;
+	if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt))
+		goto unlock;
+
+	/* Refuse the same filesystem on the same mount point */
+	err = -EBUSY;
+	if (path->mnt->mnt_sb == newmnt->mnt_sb &&
+	    path->mnt->mnt_root == path->dentry)
+		goto unlock;
+
+	err = -EINVAL;
+	if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
+		goto unlock;
+
+	newmnt->mnt_flags = mnt_flags;
+	err = graft_tree(newmnt, path);
+
+unlock:
+	up_write(&namespace_sem);
+	return err;
+}
 
 /*
  * create a new mount for userspace and request it to be added into the
@@ -1965,43 +2069,6 @@ fail:
 	return err;
 }
 
-/*
- * add a mount into a namespace's mount tree
- */
-static int do_add_mount(struct vfsmount *newmnt, struct path *path, int mnt_flags)
-{
-	int err;
-
-	mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
-
-	down_write(&namespace_sem);
-	/* Something was mounted here while we slept */
-	err = follow_down(path, true);
-	if (err < 0)
-		goto unlock;
-
-	err = -EINVAL;
-	if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt))
-		goto unlock;
-
-	/* Refuse the same filesystem on the same mount point */
-	err = -EBUSY;
-	if (path->mnt->mnt_sb == newmnt->mnt_sb &&
-	    path->mnt->mnt_root == path->dentry)
-		goto unlock;
-
-	err = -EINVAL;
-	if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
-		goto unlock;
-
-	newmnt->mnt_flags = mnt_flags;
-	err = graft_tree(newmnt, path);
-
-unlock:
-	up_write(&namespace_sem);
-	return err;
-}
-
 /**
  * mnt_set_expiry - Put a mount on an expiration list
  * @mnt: The mount to list.
@@ -2660,3 +2727,9 @@ void put_mnt_ns(struct mnt_namespace *ns)
 	kfree(ns);
 }
 EXPORT_SYMBOL(put_mnt_ns);
+
+struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
+{
+	return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
+}
+EXPORT_SYMBOL_GPL(kern_mount_data);

fs/super.c

@@ -910,29 +910,18 @@ struct dentry *mount_single(struct file_system_type *fs_type,
 }
 EXPORT_SYMBOL(mount_single);
 
-struct vfsmount *
-vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
+struct dentry *
+mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
 {
-	struct vfsmount *mnt;
 	struct dentry *root;
+	struct super_block *sb;
 	char *secdata = NULL;
-	int error;
-
-	if (!type)
-		return ERR_PTR(-ENODEV);
-
-	error = -ENOMEM;
-	mnt = alloc_vfsmnt(name);
-	if (!mnt)
-		goto out;
-
-	if (flags & MS_KERNMOUNT)
-		mnt->mnt_flags = MNT_INTERNAL;
+	int error = -ENOMEM;
 
 	if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
 		secdata = alloc_secdata();
 		if (!secdata)
-			goto out_mnt;
+			goto out;
 
 		error = security_sb_copy_data(data, secdata);
 		if (error)
@@ -944,13 +933,12 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
 		error = PTR_ERR(root);
 		goto out_free_secdata;
 	}
-	mnt->mnt_root = root;
-	mnt->mnt_sb = root->d_sb;
-	BUG_ON(!mnt->mnt_sb);
-	WARN_ON(!mnt->mnt_sb->s_bdi);
-	mnt->mnt_sb->s_flags |= MS_BORN;
+	sb = root->d_sb;
+	BUG_ON(!sb);
+	WARN_ON(!sb->s_bdi);
+	sb->s_flags |= MS_BORN;
 
-	error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata);
+	error = security_sb_kern_mount(sb, flags, secdata);
 	if (error)
 		goto out_sb;
 
@@ -961,27 +949,21 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
 	 * violate this rule. This warning should be either removed or
 	 * converted to a BUG() in 2.6.34.
 	 */
-	WARN((mnt->mnt_sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
-		"negative value (%lld)\n", type->name, mnt->mnt_sb->s_maxbytes);
+	WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
+		"negative value (%lld)\n", type->name, sb->s_maxbytes);
 
-	mnt->mnt_mountpoint = mnt->mnt_root;
-	mnt->mnt_parent = mnt;
-	up_write(&mnt->mnt_sb->s_umount);
+	up_write(&sb->s_umount);
 	free_secdata(secdata);
-	return mnt;
+	return root;
 out_sb:
-	dput(mnt->mnt_root);
-	deactivate_locked_super(mnt->mnt_sb);
+	dput(root);
+	deactivate_locked_super(sb);
 out_free_secdata:
 	free_secdata(secdata);
-out_mnt:
-	free_vfsmnt(mnt);
 out:
 	return ERR_PTR(error);
 }
 
-EXPORT_SYMBOL_GPL(vfs_kern_mount);
-
 /**
  * freeze_super - lock the filesystem and force it into a consistent state
  * @sb: the super to lock
@@ -1071,49 +1053,3 @@ out:
 	return 0;
 }
 EXPORT_SYMBOL(thaw_super);
-
-static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
-{
-	int err;
-	const char *subtype = strchr(fstype, '.');
-	if (subtype) {
-		subtype++;
-		err = -EINVAL;
-		if (!subtype[0])
-			goto err;
-	} else
-		subtype = "";
-
-	mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
-	err = -ENOMEM;
-	if (!mnt->mnt_sb->s_subtype)
-		goto err;
-	return mnt;
-
- err:
-	mntput(mnt);
-	return ERR_PTR(err);
-}
-
-struct vfsmount *
-do_kern_mount(const char *fstype, int flags, const char *name, void *data)
-{
-	struct file_system_type *type = get_fs_type(fstype);
-	struct vfsmount *mnt;
-	if (!type)
-		return ERR_PTR(-ENODEV);
-	mnt = vfs_kern_mount(type, flags, name, data);
-	if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
-	    !mnt->mnt_sb->s_subtype)
-		mnt = fs_set_subtype(mnt, fstype);
-	put_filesystem(type);
-	return mnt;
-}
-EXPORT_SYMBOL_GPL(do_kern_mount);
-
-struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
-{
-	return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
-}
-
-EXPORT_SYMBOL_GPL(kern_mount_data);