fs: Add VirtualBox guest shared folder (vboxsf) support

VirtualBox hosts can share folders with guests, this commit adds a
VFS driver implementing the Linux-guest side of this, allowing folders
exported by the host to be mounted under Linux.

This driver depends on the guest <-> host IPC functions exported by
the vboxguest driver.
Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

MAINTAINERS

@@ -17610,6 +17610,12 @@ F:	include/linux/vbox_utils.h
 F:	include/uapi/linux/vbox*.h
 F:	drivers/virt/vboxguest/
 
+VIRTUAL BOX SHARED FOLDER VFS DRIVER:
+M:	Hans de Goede <hdegoede@redhat.com>
+L:	linux-fsdevel@vger.kernel.org
+S:	Maintained
+F:	fs/vboxsf/*
+
 VIRTUAL SERIO DEVICE DRIVER
 M:	Stephen Chandler Paul <thatslyude@gmail.com>
 S:	Maintained

fs/Kconfig

@@ -264,6 +264,7 @@ source "fs/pstore/Kconfig"
 source "fs/sysv/Kconfig"
 source "fs/ufs/Kconfig"
 source "fs/erofs/Kconfig"
+source "fs/vboxsf/Kconfig"
 
 endif # MISC_FILESYSTEMS
 

fs/Makefile

@@ -133,3 +133,4 @@ obj-$(CONFIG_CEPH_FS)		+= ceph/
 obj-$(CONFIG_PSTORE)		+= pstore/
 obj-$(CONFIG_EFIVAR_FS)		+= efivarfs/
 obj-$(CONFIG_EROFS_FS)		+= erofs/
+obj-$(CONFIG_VBOXSF_FS)		+= vboxsf/

fs/vboxsf/Kconfig

+config VBOXSF_FS
+	tristate "VirtualBox guest shared folder (vboxsf) support"
+	depends on X86 && VBOXGUEST
+	select NLS
+	help
+	  VirtualBox hosts can share folders with guests, this driver
+	  implements the Linux-guest side of this allowing folders exported
+	  by the host to be mounted under Linux.
+
+	  If you want to use shared folders in VirtualBox guests, answer Y or M.

fs/vboxsf/Makefile

+# SPDX-License-Identifier: MIT
+
+obj-$(CONFIG_VBOXSF_FS) += vboxsf.o
+
+vboxsf-y := dir.o file.o utils.o vboxsf_wrappers.o super.o

fs/vboxsf/vfsmod.h

+/* SPDX-License-Identifier: MIT */
+/*
+ * VirtualBox Guest Shared Folders support: module header.
+ *
+ * Copyright (C) 2006-2018 Oracle Corporation
+ */
+
+#ifndef VFSMOD_H
+#define VFSMOD_H
+
+#include <linux/backing-dev.h>
+#include <linux/idr.h>
+#include "shfl_hostintf.h"
+
+#define DIR_BUFFER_SIZE SZ_16K
+
+/* The cast is to prevent assignment of void * to pointers of arbitrary type */
+#define VBOXSF_SBI(sb)	((struct vboxsf_sbi *)(sb)->s_fs_info)
+#define VBOXSF_I(i)	container_of(i, struct vboxsf_inode, vfs_inode)
+
+struct vboxsf_options {
+	unsigned long ttl;
+	kuid_t uid;
+	kgid_t gid;
+	bool dmode_set;
+	bool fmode_set;
+	umode_t dmode;
+	umode_t fmode;
+	umode_t dmask;
+	umode_t fmask;
+};
+
+struct vboxsf_fs_context {
+	struct vboxsf_options o;
+	char *nls_name;
+};
+
+/* per-shared folder information */
+struct vboxsf_sbi {
+	struct vboxsf_options o;
+	struct shfl_fsobjinfo root_info;
+	struct idr ino_idr;
+	spinlock_t ino_idr_lock; /* This protects ino_idr */
+	struct nls_table *nls;
+	u32 next_generation;
+	u32 root;
+	int bdi_id;
+};
+
+/* per-inode information */
+struct vboxsf_inode {
+	/* some information was changed, update data on next revalidate */
+	int force_restat;
+	/* list of open handles for this inode + lock protecting it */
+	struct list_head handle_list;
+	/* This mutex protects handle_list accesses */
+	struct mutex handle_list_mutex;
+	/* The VFS inode struct */
+	struct inode vfs_inode;
+};
+
+struct vboxsf_dir_info {
+	struct list_head info_list;
+};
+
+struct vboxsf_dir_buf {
+	size_t entries;
+	size_t free;
+	size_t used;
+	void *buf;
+	struct list_head head;
+};
+
+/* globals */
+extern const struct inode_operations vboxsf_dir_iops;
+extern const struct inode_operations vboxsf_lnk_iops;
+extern const struct inode_operations vboxsf_reg_iops;
+extern const struct file_operations vboxsf_dir_fops;
+extern const struct file_operations vboxsf_reg_fops;
+extern const struct address_space_operations vboxsf_reg_aops;
+extern const struct dentry_operations vboxsf_dentry_ops;
+
+/* from utils.c */
+struct inode *vboxsf_new_inode(struct super_block *sb);
+void vboxsf_init_inode(struct vboxsf_sbi *sbi, struct inode *inode,
+		       const struct shfl_fsobjinfo *info);
+int vboxsf_create_at_dentry(struct dentry *dentry,
+			    struct shfl_createparms *params);
+int vboxsf_stat(struct vboxsf_sbi *sbi, struct shfl_string *path,
+		struct shfl_fsobjinfo *info);
+int vboxsf_stat_dentry(struct dentry *dentry, struct shfl_fsobjinfo *info);
+int vboxsf_inode_revalidate(struct dentry *dentry);
+int vboxsf_getattr(const struct path *path, struct kstat *kstat,
+		   u32 request_mask, unsigned int query_flags);
+int vboxsf_setattr(struct dentry *dentry, struct iattr *iattr);
+struct shfl_string *vboxsf_path_from_dentry(struct vboxsf_sbi *sbi,
+					    struct dentry *dentry);
+int vboxsf_nlscpy(struct vboxsf_sbi *sbi, char *name, size_t name_bound_len,
+		  const unsigned char *utf8_name, size_t utf8_len);
+struct vboxsf_dir_info *vboxsf_dir_info_alloc(void);
+void vboxsf_dir_info_free(struct vboxsf_dir_info *p);
+int vboxsf_dir_read_all(struct vboxsf_sbi *sbi, struct vboxsf_dir_info *sf_d,
+			u64 handle);
+
+/* from vboxsf_wrappers.c */
+int vboxsf_connect(void);
+void vboxsf_disconnect(void);
+
+int vboxsf_create(u32 root, struct shfl_string *parsed_path,
+		  struct shfl_createparms *create_parms);
+
+int vboxsf_close(u32 root, u64 handle);
+int vboxsf_remove(u32 root, struct shfl_string *parsed_path, u32 flags);
+int vboxsf_rename(u32 root, struct shfl_string *src_path,
+		  struct shfl_string *dest_path, u32 flags);
+
+int vboxsf_read(u32 root, u64 handle, u64 offset, u32 *buf_len, u8 *buf);
+int vboxsf_write(u32 root, u64 handle, u64 offset, u32 *buf_len, u8 *buf);
+
+int vboxsf_dirinfo(u32 root, u64 handle,
+		   struct shfl_string *parsed_path, u32 flags, u32 index,
+		   u32 *buf_len, struct shfl_dirinfo *buf, u32 *file_count);
+int vboxsf_fsinfo(u32 root, u64 handle, u32 flags,
+		  u32 *buf_len, void *buf);
+
+int vboxsf_map_folder(struct shfl_string *folder_name, u32 *root);
+int vboxsf_unmap_folder(u32 root);
+
+int vboxsf_readlink(u32 root, struct shfl_string *parsed_path,
+		    u32 buf_len, u8 *buf);
+int vboxsf_symlink(u32 root, struct shfl_string *new_path,
+		   struct shfl_string *old_path, struct shfl_fsobjinfo *buf);
+
+int vboxsf_set_utf8(void);
+int vboxsf_set_symlinks(void);
+
+#endif