/* Copyright (C) 2005,2006 David Decotigny
    Copyright (C) 2000-2005 The KOS Team (Thomas Petazzoni, David
                            Decotigny, Julien Munier)
 
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.
    
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
    
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
    USA. 
 */
 #ifndef _SOS_FS_H_
 #define _SOS_FS_H_
 
 
 /**
  * @file fs.h
  *
  * (Virtual) Filesystem management.
  *
  * SOS provides a complete Unix-like file system service. Supported
  * features of this service are:
  *   - mountpoints
  *   - generic file system support (FS) through object-oriented
  *     specialization (so-called VFS)
  *   - hard & symbolic links
  *   - regular files and directories
  *   - block and character device special files (from article 9 onward)
  *   - file mapping
  *   - basic permission management ("rwx" only, no notion of owner)
  *   - chroot
  *   - separation of disk node and namespace notions allowing hard links
  *     and to move/rename/remove files or directories that are in use
  *   - basic FS interface (open/read/seek/creat/mkdir/rename/link
  *     / symlink/chmod/mount/fcntl/ioctl...)
  *   - deferred writes (ie file caching). @see sync(3)
  *
  * Among the unsupported features:
  *   - no user-based permission (uid/gid, ACLS)
  *   - no modification / access time accounting
  *   - no Fifo/socket special files (yet)
  *   - no generic support library for common fcntl commands
  *     (F_SETOWN/GETLEASE/NOTIFY, etc.)
  *   - no flock-style functions
  *
  * Rationale
  * =========
  * The VFS layer is based on 3 central concepts:
  *
  *  - The meta-information for each file stored on disk: size,
  *    permissions, ... (struct sos_fs_node for SOS, inode for Unix)
  *
  *    It is sufficient to know where this meta-information is located
  *    on disk (a simple sector number most of the time) to build the
  *    corresponding struct sos_fs_node into memory and to retrieve the
  *    data of the file from the disk
  *
  *    For example, consider that we know a sector that holds the meta
  *    information is located at sector 64589 on disk. By retrieving
  *    this meta information directly from disk, we can build the
  *    struct sos_fs_node, which would (for example) tell that the
  *    corresponding file spans (for example) over sectors 4345, 5645,
  *    4539 and 6575, is 1.7kB long
  *
  *    Everything is stored this way on the disk, even the
  *    directories. From the disk contents' point of view, a directory
  *    is simply a file whose contents represent a list of mappings
  *    "name" -> meta-information location
  *
  *  - One or many nodes in the file hierarchy pointing to this data
  *    (struct sos_fs_nscache_node for SOS, struct dentry for Linux). This
  *    tells that the entry "toto" in directory "/home/zorglub"
  *    corresponds to the given struct sos_fs_node
  *
  *    Actually, with the struct sos_fs_node above, we can reach any
  *    file in the system. However, dealing with mountpoints requires
  *    an intermediary data structure because a directory on a disk
  *    cannot make reference to children struct sos_fs_node on other
  *    disk. This is one of the reasons why there is this struct
  *    sos_fs_nscache_node. Another reason is that we kind-of "cache" the
  *    most used struct sos_fs_node: those that lead from the global
  *    root ("/") to the files and directories currently being used
  *    (hence the name "nscache" for "namespace cache"). This speeds-up
  *    the path-resolving process (aka "lookup"), as the most-used path
  *    are already in-memory and the struct sos_fs_node are already
  *    in-memory too.
  *
  *    A struct sos_fs_nscache_node can have at most 1 parent (the ".."
  *    entry). It can also have 0 parent in case the node is being used
  *    by a process (file is opened or mapped), but the file is
  *    actually "removed", ie un-reachable from any directory.
  *
  *    Many such structures can reference the same underlying struct
  *    sos_fs_node, which enables the support of "hard links".
  *
  *  - The "opened file" strucures. They store the information
  *    pertaining to a particular usage of a file. The most important
  *    thing they store is the "file pointer", which holds the
  *    location in the file where the next read/write operation should
  *    start
  *
  *    Each process has at least 2 such opened files: its "current
  *    working directory" (RTFM chdir) and its "process root" (RTFM
  *    chroot). Those are heritated across fork() and can be changed by
  *    appropriate syscalls (resp. chdir/chroot). The main "root" of
  *    the system is the process root of the "init" process. The usual
  *    opened files (think of open() and opendir()) are stored in the
  *    file descriptor array (fds[]). This is the index in this array
  *    that is commonly called a "file descriptor".
  *
  *
  * The whole VFS layer comprises a series of objects that can be
  * specialized to implement different FS support (fat, ext2, ffs, ...):
  *
  *  - The notion of "file system manager", which basically is a
  *    container to a FS name (eg "FAT", "EXT2", etc...) and a series of
  *    functions responsible for initializing a particular "mounting" of
  *    a FS (the "mount" method). This is SOS's struct sos_fs_manager_type
  *
  *  - The notion of "file system instance" which contains the data
  *    proper to a particular mounting of an FS. Its most important job
  *    is to allocate new struct sos_fs_node on disk, or to retrieve the
  *    meta-information (ie struct sos_fs_node) located at the given
  *    location on disk. This is roughly THE primary physical interface
  *    between the VFS and the disks. This is SOS's struct
  *    sos_fs_manager_instance, aka the Linux's superblock
  *
  *    For each struct sos_fs_node that it allocates, or that is loads
  *    from disk into memory, this "instance manager" is responsible
  *    for inidicating the functions that implement the FS-dedicated
  *    routine such as read/write/mmap/ioctl/... for this precise node.
  *
  *    The nodes (struct sos_fs_node) of a struct
  *    sos_fs_manager_instance that are currently loaded in memory are
  *    stored in a hash-table. The key of this map is the location of the
  *    meta-information on disk. That way, it is very fast to look for
  *    the given meta-information whose location on disk is knows: if
  *    it has already been loaded into memory, its memory address is
  *    quickly resolved thanks to this hash table.
  */
 
 #include <sos/types.h>
 #include <sos/errno.h>
 #include <sos/hash.h>
 #include <sos/umem_vmm.h>
 
 /* Forward declarations (structures defined in this file) */
 struct sos_fs_manager_type;
 struct sos_fs_manager_instance;
 struct sos_fs_statfs;
 struct sos_fs_node;
 struct sos_fs_opened_file;
 struct sos_fs_stat;
 
 #include "fs_nscache.h"
 #include <sos/blkdev.h>
 
 /**
  * The type of filesystem object.
  *
  * Each struct sos_fs_node has a type. Here are the supported types.
  */
 typedef enum {
   SOS_FS_NODE_REGULAR_FILE = 0x42,
   SOS_FS_NODE_DIRECTORY    = 0x24,
   SOS_FS_NODE_SYMLINK      = 0x84,
   SOS_FS_NODE_DEVICE_CHAR  = 0x48,
   SOS_FS_NODE_DEVICE_BLOCK = 0x12
 } sos_fs_node_type_t;
 
 
 #define SOS_FS_MANAGER_NAME_MAXLEN 32
 /**
  * Description of a supported Filesystem type.
  *
  * These descriptions are listed in an internal list (see
  * fs.c:fs_list), and each time we want to mount a FS, we precise a
  * name (eg "FAT", "EXT2", ...). The VFS will look for this name into
  * the list of supported filesystem types, and, when found, call its
  * sos_fs_manager_type::mount() method.
  *
  * New filesystem types are registered using sos_fs_register_fs_type()
  */
 struct sos_fs_manager_type
 {
   char name[SOS_FS_MANAGER_NAME_MAXLEN];
 
   /**
    * Responsible for making sure the underlying device (if any) really
    * stores the correct filesystem format, for creating the hash of fs
    * nodes and for calling sos_fs_register_fs_instance
    *
    * @param device May be NULL
    *
    * @note mandatory, may block
    */
   sos_ret_t (*mount)(struct sos_fs_manager_type * this,
                      struct sos_fs_node * device,
                      const char * args,
                      struct sos_fs_manager_instance ** mounted_fs);
   
   /**
    * Responsible for de-allocating the hash of fs nodes and for
    * calling sos_fs_unregister_fs_instance
    *
    * @note mandatory, may block
    */
   sos_ret_t (*umount)(struct sos_fs_manager_type * this,
                       struct sos_fs_manager_instance * mounted_fs);
 
   /** Free of use */
   void * custom_data;
 
   /** List of filesystem instances of this type currently mounted
       somewhere in the system */
   struct sos_fs_manager_instance * instances;
 
   /** Linkage for the list of filesystem types registered in the
       system */
   struct sos_fs_manager_type *prev, *next;
 };
 
 
 /**
  * Data related to a particular "mounting" of a file system. A
  * so-called "superblock" under Linux
  *
  * This holds the FUNDAMENTAL functions responsible for loading struct
  * sos_fs_node from disk, or for allocating thom on disk. It also
  * holds the hash-table of struct sos_fs_node already loaded into
  * memory.
  */
 struct sos_fs_manager_instance
 {
   /**
    * @note Publicly readable. Written only by sos_fs_manager_type::mount()
    */
   struct sos_fs_manager_type * fs_type;
 
   /**
    * Usually, a filesystem relies on a device (disk, network, ram,
    * ...) to fetch its data. This is the location of the device.
    *
    * @note Publicly readable. Written only by fs.c
    */
   struct sos_fs_node * device;
 
 #define SOS_FS_MOUNT_SYNC     (1 << 0)
 #define SOS_FS_MOUNT_READONLY (1 << 1)
 #define SOS_FS_MOUNT_NOEXEC   (1 << 2)
   /**
    * Is this FS read-only, without EXEC file permission, write-through
    * ? Or-red combination of the SOS_FS_MOUNT_ flags
    *
    * @note Publicly readable. Written only by fs.c
    */
   sos_ui32_t flags;
 
   /**
    * The namespace node that is the root of THIS file system mounting
    *
    * @note Publicly readable. Written only by fs.c
    */
   struct sos_fs_nscache_node * root;
 
   /**
    * List of dirty nodes. These are the nodes that need to be written
    * back to disk. With FS supporting deferred-writes, the
    * sos_fs_sync() function will use this list to flush the dirty
    * nodes back to disk.
    *
    * @note Reserved to fs.c
    */
   struct sos_fs_node * dirty_nodes;
 
   /**
    * Build a fresh new FS node at the given location. This implies
    * the allocation of a new sos_fs_node structure in memory
    *
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    */
   sos_ret_t (*fetch_node_from_disk)(struct sos_fs_manager_instance * this,
                                     sos_ui64_t storage_location,
                                     struct sos_fs_node ** result);
 
   /**
    * Build a fresh new FS node ON THE DISK of the given type (dir,
    * plain file, symlink, ...), completely empty ; return a newly
    * allocated IN-MEMORY node structure representing it
    *
    * @param open_creat_flags is the open_flags parameter passed to
    * sos_fs_open() when O_CREAT is set. 0 when allocated trough
    * creat/mkdir/mknod/symlink
    *
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    */
   sos_ret_t (*allocate_new_node)(struct sos_fs_manager_instance * this,
                                  sos_fs_node_type_t type,
                                  const struct sos_process * creator,
                                  sos_ui32_t access_rights,
                                  sos_ui32_t open_creat_flags,
                                  struct sos_fs_node ** result);
 
   /**
    * Return filesystem status (RTFM df)
    *
    * @note Optional, may block. Appropriate locking MUST be implemented
    */
   sos_ret_t (*statfs)(struct sos_fs_manager_instance * this,
                       struct sos_fs_statfs * result);
 
   /**
    * Comparison callback called when looking for file/dirs in the
    * namespace cache. Normally, a usual lexicographical comparison is
    * done (when this function points to NULL). But for some FS, it
    * might be useful to use another comparison function (eg for
    * case-insensitive FS)
    *
    * @note Optional (may be NULL), must NOT block
    */
   sos_bool_t (*nsnode_same_name)(const char * name1, sos_ui16_t namelen1,
                                  const char * name2, sos_ui16_t namelen2);
 
   /**
    * Hash table of the struct sos_fs_node of this filesystem instance
    * loaded in memory: key=storage_location, element=sos_fs_node
    */
   struct sos_hash_table * nodecache;
 
   /**
    * Unique identifier of this FS (used in sync method, updated by
    * fs.c). This enables sync_all_fs to be resilient to mount/umount
    * and (un)register_fs_type/instance
    */
   sos_ui64_t uid;
 
   void * custom_data;
 
   /** Linkage for the list of instances for the underlying fs type */
   struct sos_fs_manager_instance * prev, * next;
 };
 
 
 /**
  * The CENTRAL data structure of the whole thing. A so-called "inode"
  *
  * This represents the meta-information related to a file on disk: its
  * permission, where its data is located. Actually, in SOS, these
  * information are not stored in this structure. Instead, we define a
  * series of methods in this structure that MUST be implemented by the
  * FS and that realize the higher level operations needed by the
  * OS. These operations will rely on the meta-information that the FS
  * code MUST define and manage by itself (hence the
  * sos_fs_node::custom_data field).
  */
 struct sos_fs_node
 {
   /**
    * An struct sos_fs_node always belong to exactly ONE file system
    */
   struct sos_fs_manager_instance * fs;
 
   /**
    * The so-called "inode": location of this node inside the FS
    * instance. Updated by struct
    * sos_fs_manager_instance::fetch_node_from_disk()
    */
   sos_ui64_t storage_location;
 
   /**
    * Number of ON-DISK links to this node.
    *
    * - For everything but directories: the number of hard links to the file
    * - For directories: 1 + the number of children nodes
    *
    * @note Publicly readable. Written only by
    * sos_fs_node_ops_dir::link() and sos_fs_node_ops_dir::unlink()
    */
   sos_count_t ondisk_lnk_cnt;
 
   /**
    * Number of IN-MEMORY nscache_nodes referencing this FS node.
    *
    * Corresponds to the number of struct sos_fs_nscache_node pointing
    * to this node. This could be as much as ondisk_lnk_cnt + 1, but is
    * usually less
    *
    * @note Reserved to fs.c
    */
   sos_count_t inmem_ref_cnt;
 
   /**
    * Directory, symlink, ...
    *
    * @see sos_fs_node_type_t
    *
    * @note Publicly readable. Written only by fs.c
    */
   sos_fs_node_type_t type;
 
 #define SOS_FS_READABLE          00400
 #define SOS_FS_WRITABLE          00200
 #define SOS_FS_EXECUTABLE        00100
   /**
    * read/write, ... @see the SOS_FS_*ABLE flags
    * @note Publicly readable. Written only by fs.c
    */
   sos_ui32_t access_rights;
 
   /**
    * @note Reserved to fs.c
    */
   sos_bool_t dirty;
 
   /**
    * Incremented each time one of the opened files for this node is
    * modified
    * @note Publicly readable. Written only by fs.c
    */
   sos_lcount_t generation;
 
   /**
    * @note Available only for device files (char/block)
    * @note Publicly readable. Written only by
    * sos_fs_manager_instance::fetch_node_from_disk() and mknod()
    */
   struct sos_fs_dev_id_t
   {
     sos_ui32_t device_class;    /**< aka "major" */
     sos_ui32_t device_instance; /**< aka "minor" */
   } dev_id;
 
   /** Operations common to all node types */
   struct sos_fs_node_ops_file  *ops_file;
 
   /** Operations specific to some node types */
   union
   {
     /** when type == SOS_FS_NODE_DIRECTORY */
     struct sos_fs_node_ops_dir      *ops_dir;
 
     /**
      * when type == SOS_FS_NODE_DEVICE_BLOCK
      * The FS node has a link to some data pertaining to the device,
      * not to any special operations
      * @see blkdev.c for a definition of this structure
      */
     struct sos_blockdev_instance *block_device;
 
     /** when type == SOS_FS_NODE_SYMLINK */
     struct sos_fs_node_ops_symlink  *ops_symlink;
   }; /* Anonymous union (gcc extension) */
 
 
   /**
    * Simply free this FS node from the kernel memory: it does NOT
    * mean that the corresponding on-disk node is free ! Actually, the
    * corresponding ON-DISK node is free iff ondisk_lnk_cnt == 0. No
    * need to sync anything to disk, as the VFS will sync the node
    * before calling this method
    *
    * @note Mandatory, may block, no special locking needed
    */
   sos_ret_t (*destructor)(struct sos_fs_node * this);
 
   /**
    * Called when a process opens the node
    *
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    * @note FS-specific EXCPET for device special files (char &
    * block) because they are handled in an uniform way by the
    * chardev/blockdev subsystems
    * @note As a consequence, FS code can safely assume that "this" is
    * never a character or block device
    */
   sos_ret_t (*new_opened_file)(struct sos_fs_node * this,
                                const struct sos_process * owner,
                                sos_ui32_t open_flags,
                                struct sos_fs_opened_file ** result_of);
 
   /**
    * Called when a process opens the node
    *
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    * @note FS-specific EXCEPT for device special files (char &
    * block) because they are handled in an uniform way by the
    * chardev/blockdev subsystems
    * @note As a consequence, FS code can safely assume that "this" is
    * never a character or block device
    */
   sos_ret_t (*close_opened_file)(struct sos_fs_node * this,
                                  struct sos_fs_opened_file * of);
 
   /**
    * This should hold the meta information for this node as needed by
    * the FS instance.
    */
   void * custom_data;
 
   /** Hash linkage entry for this FS node in the nodecache
      dictionary */
   struct sos_hash_linkage hlink_nodecache;
 
   /** Linkage to list the dirty nodes of the given FS */
   struct sos_fs_node *prev_dirty, *next_dirty;
 };
 
 
 
 /**
  * The list of methods implementing the basic VFS operations on the
  * given struct sos_fs_node
  *
  * @see sos_fs_node::ops_file
  */
 struct sos_fs_node_ops_file
 {
   /**
    * Change size of file
    *
    * @note Optional, may block. Appropriate locking MUST be implemented
    */
   sos_ret_t (*truncate)(struct sos_fs_node *this,
                         sos_lsoffset_t length);
 
   /**
    * Retrieve the status (eg size) of the file
    *
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    */
   sos_ret_t (*stat)(struct sos_fs_node * this,
                     struct sos_fs_stat * result);
 
   /**
    * Change the sos_fs_node::access_rights attribute
    *
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    */
   sos_ret_t (*chmod)(struct sos_fs_node * this,
                      sos_ui32_t new_access_rights);
 
 
   /**
    * Flush any change to the node back to the file system backing store
    *
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    */
   sos_ret_t (*sync)(struct sos_fs_node *this);
 };
 
 
 /**
  * The list of methods implementing the basic VFS symlink operations
  *
  * @see sos_fs_node::ops_symlink
  */
 struct sos_fs_node_ops_symlink
 {
   /**
    * Used by the _kernel_ to resolve the symlinks. To change/create a
    * symlink target, it is needed only from userland: the read/write
    * methods are made for this
    *
    * @param target Pointer to the string representing the target's
    * path, allocated for the fs_node's lifetime !
    *
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    */
   sos_ret_t (*expand)(struct sos_fs_node *this,
                       char const  ** target,
                       sos_size_t * target_len);
 };
 
 
 /**
  * The list of methods implementing the basic VFS directory operations
  *
  * @see sos_fs_node::ops_dir
  */
 struct sos_fs_node_ops_dir
 {
   /**
    * Look for the on-disk location of the sos_fs_node having the given
    * name
    *
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    */
   sos_ret_t (*lookup)(struct sos_fs_node *this,
                       const char * name, sos_ui16_t namelen,
                       sos_ui64_t * result_storage_location);
 
   /**
    * Add a new reference in the current sos_fs_node to the on-disk
    * location of the given sos_fs_node
    *
    * @note Responsible for updating this->ondisk_lnk_cnt
    * @note Mandatory for writable directories, may block. Appropriate
    * locking MUST be implemented
    */
   sos_ret_t (*link)(struct sos_fs_node *this,
                     const struct sos_process *actor,
                     const char * entry_name, sos_ui16_t entry_namelen,
                     struct sos_fs_node * node);
 
   /**
    * Remove the entry in the current sos_fs_node for the on-disk
    * location with the given name
    *
    * @note Responsible for updating this->ondisk_lnk_cnt
    * @note Mandatory for writable directories, may block. Appropriate
    * locking MUST be implemented
    */
   sos_ret_t (*unlink)(struct sos_fs_node *this,
                       const struct sos_process *actor,
                       const char * entry_name, sos_ui16_t entry_namelen);
 };
 
 
 /**
  * The data structure holding information and method related to a
  * particular usage of a file. A so-called "struct file"
  *
  * This represents the kernel structure behind a "file descriptor" or
  * behind a chdir/chroot. Among other things, it holds the methods
  * responsible for reading/writing into the file, and for moving the
  * file pointer (see @sos_fs_opened_file::position) inside it.
  */
 struct sos_fs_opened_file
 {
   /** The process that opened the file/dir */
   const struct sos_process * owner;
 
   /**
    * The reference to the sos_fs_nscache_node and, hence, to the underlying sos_fs_node.
    *
    * Used to cache the in-memory fs nodes
    */
   struct sos_fs_nscache_node * direntry;
 
   /** Use for memory-management */
   sos_count_t ref_cnt;
 
   /**
    * Always > 0 (ie max size = 2^63-1 = 9.2 10^18). We make it
    * "signed" here to limit its range. Because we must be able to
    * seek to the begining of the file with SEEK_END and a negative
    * offset, so the max size of the file must be reachable by a lseek
    * offset
    *
    * @note reserved to filesystem instance code. Not modified nor used
    * by fs.c
    */
   sos_lsoffset_t     position;
 
   /**
    * Incremented each time this opened file is modified
    *
    * Used to implement a readdir method resilient to
    * creat/mkdir/rmdir/unlink
    */
   sos_lcount_t generation;
 
   /**
    * @see SOS_FS_OPEN_* flags
    */
   sos_ui32_t open_flags;
 
   /** Operations common to all node types */
   struct sos_fs_ops_opened_file * ops_file;
 
   /** Operations specific to some node types */
   union
   {
     /** when direntry->fs_node->type == SOS_FS_NODE_DIRECTORY */
     struct sos_fs_ops_opened_dir      * ops_dir;
 
     /** when direntry->fs_node->type == SOS_FS_NODE_DEVICE_CHAR */
     struct sos_fs_ops_opened_chardev  * ops_chardev;
 
     /** when direntry->fs_node->type == SOS_FS_NODE_DEVICE_BLOCK */
     struct sos_fs_ops_opened_blockdev * ops_blockdev;
   }; /* Anonymous union (gcc extension) */
 
   /**
    * Called upon fork() to duplicate all the opened files
    *
    * @note FS-specific EXCEPT for device special files (char &
    * block) because they are handled in an uniform way by the
    * chardev/blockdev subsystems
    * @note As a consequence, FS code can safely assume that "this" is
    * never a character or block device
    */
   sos_ret_t (*duplicate)(struct sos_fs_opened_file *this,
                          const struct sos_process  * for_owner,
                          struct sos_fs_opened_file **result);
 
   void * custom_data;
 };
 
 
 /**
  * Reference position for sos_fs_seek
  */
 typedef enum { SOS_SEEK_SET=42,
                SOS_SEEK_CUR=24,
                SOS_SEEK_END=84 } sos_seek_whence_t;
 /**
  * The list of methods implementing the basic VFS opened file
  * operations
  *
  * See the Unix manual pages, they basically form the interfaces to to
  * these functions
  *
  * @see sos_fs_opened_file::ops_file
  */
 struct sos_fs_ops_opened_file
 {
   /**
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    * @note Please call sos_fs_mark_dirty() if disk contents is changed
    */
   sos_ret_t (*seek)(struct sos_fs_opened_file *this,
                     sos_lsoffset_t offset,
                     sos_seek_whence_t whence,
                     /* out */ sos_lsoffset_t * result_position);
 
   /**
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    * @note Please call sos_fs_mark_dirty() if disk contents is changed
    */
   sos_ret_t (*read)(struct sos_fs_opened_file *this,
                     sos_uaddr_t dest_buf,
                     sos_size_t * /* in/out */len);
 
   /**
    * @note Optional (might be NULL), may block. Appropriate locking
    * MUST be implemented
    * @note Please call sos_fs_mark_dirty() if disk contents is changed
    */
   sos_ret_t (*write)(struct sos_fs_opened_file *this,
                      sos_uaddr_t src_buf,
                      sos_size_t * /* in/out */len);
 
   /**
    * @note Optional (might be NULL), may block. Appropriate locking
    * MUST be implemented
    * @note Please call sos_fs_mark_dirty() if disk contents is changed
    */
   sos_ret_t (*mmap)(struct sos_fs_opened_file *this,
                     sos_uaddr_t *uaddr, sos_size_t size,
                     sos_ui32_t access_rights,
                     sos_ui32_t flags,
                     sos_luoffset_t offset);
 
   /**
    * @note Optional (might be NULL), may block. Appropriate locking
    * MUST be implemented
    * @note Please call sos_fs_mark_dirty() if disk contents is changed
    */
   sos_ret_t (*fcntl)(struct sos_fs_opened_file *this,
                      int req_id,
                      sos_ui32_t req_arg /* Usually: sos_uaddr_t */);
 };
 
 
 /**
  * The list of methods implementing the basic VFS opened character device
  * operations
  *
  * @see sos_fs_opened_file::ops_file
  */
 struct sos_fs_ops_opened_chardev
 {
   /**
    * @note Optional (might be NULL), may block. Appropriate locking
    * MUST be implemented
    * @note Please call sos_fs_mark_dirty() if disk contents is changed
    */
   sos_ret_t (*ioctl)(struct sos_fs_opened_file *this,
                      int req_id,
                      sos_ui32_t req_arg /* Usually: sos_uaddr_t */);
 };
 
 
 /**
  * The list of methods implementing the basic VFS opened block device
  * operations
  *
  * @see sos_fs_opened_file::ops_file
  */
 struct sos_fs_ops_opened_blockdev
 {
   /**
    * @note Optional (might be NULL), may block. Appropriate locking
    * MUST be implemented
    * @note Please call sos_fs_mark_dirty() if disk contents is changed
    */
   sos_ret_t (*ioctl)(struct sos_fs_opened_file *this,
                      int req_id,
                      sos_ui32_t req_arg /* Usually: sos_uaddr_t */);
 };
 
 
 /** Data structure that is to be filled by readdir */
 struct sos_fs_dirent
 {
   sos_ui64_t storage_location;
   sos_si64_t offset_in_dirfile;
   sos_ui32_t type;
   sos_ui16_t namelen;
 
 #define SOS_FS_DIRENT_NAME_MAXLEN 128
   char       name[SOS_FS_DIRENT_NAME_MAXLEN];
 };
 
 
 /**
  * The list of methods implementing the basic VFS opened directory
  * operations
  *
  * @see sos_fs_opened_file::ops_file
  */
 struct sos_fs_ops_opened_dir
 {
   /**
    * Each time it is called, responsible for filling the sos_fs_dirent
    * structure, return -SOS_ENOENT when done.
    *
    * @note Mandatory, may block. Appropriate locking MUST be implemented
    * @note Please call sos_fs_mark_dirty() if disk contents is changed
    */
   sos_ret_t (*readdir)(struct sos_fs_opened_file *this,
                        struct sos_fs_dirent * result);
 };
 
 
 
 /**
  * Used by the stat calls
  *
  * @see sos_fs_node_ops_file::stat
  */
 struct sos_fs_stat
 {
   struct sos_fs_dev_id_t st_rdev;
   sos_fs_node_type_t     st_type;
   sos_ui64_t             st_storage_location;
   sos_ui32_t             st_access_rights;
   sos_count_t            st_nlink;
   sos_si64_t             st_size;
 };
 
 
 /**
  * Used by the statvfs calls
  *
  * @see sos_fs_manager_instance::statfs
  */
 struct sos_fs_statfs
 {
   struct sos_fs_dev_id_t f_rdev;
   sos_size_t             f_sz_total;  /**< Total size */
   sos_size_t             f_sz_free;   /**< Size left on device */
   sos_count_t            f_node_total;/**< Total allocatable FS nodes */
   sos_count_t            f_node_avail;/**< Number of available free FS nodes */
   sos_ui32_t             f_flags;
 };
 
 
 /**
  * Must be called AFTER the FS manager types needed to mount the root
  * filesystem have been registered
  */
 sos_ret_t sos_fs_subsystem_setup(const char * root_device,
                                  const char * fs_type,
                                  const char * mount_args,
                                  struct sos_fs_manager_instance ** result_rootfs);
 
 
 /*  ***************************************************************
  * The Following functions are relatively standard
  *
  * @see Unix manual pages for details
  */
 
 
 /**
  * mount a file system
  *
  * @param actor process calling mount
  * @param _src_path(len) may be NULL (as for virtfs or /proc)
  * @fsname the name of the filesystem type to mount
  * @args any args passed to the sos_fs_manager_type::mount method
  * @result_fs the resulting filesystem instance
  */
 sos_ret_t sos_fs_mount(struct sos_process * actor,
                        const char * _src_path,
                        sos_size_t _src_pathlen,
                        const char * _dst_path,
                        sos_size_t _dst_pathlen,
                        const char * fsname,
                        sos_ui32_t mountflags,
                        const char * args,
                        struct sos_fs_manager_instance ** /*out*/result_fs);
 
 /**
  * unmount the filesystem at the given location
  */
 sos_ret_t sos_fs_umount(struct sos_process * actor,
                         const char * _mountpoint_path,
                         sos_size_t _mountpoint_pathlen);
 
 /**
  * Flush all the dirty nodes of all the FS to disk
  */
 sos_ret_t sos_fs_sync_all_fs(void);
 
 /**
  * Retrieve filesystem status, or return -SOS_ENOSYS if filesystem
  * cannot report this
  */
 sos_ret_t sos_fs_vfstat(const struct sos_process * actor,
                         const char * _path,
                         sos_size_t _pathlen,
                         struct sos_fs_statfs * result);
 
 /**
  * Open flags
  */
 #define SOS_FS_OPEN_EXCL        (1 << 0)
 #define SOS_FS_OPEN_CREAT       (1 << 1)
 #define SOS_FS_OPEN_TRUNC       (1 << 2)
 #define SOS_FS_OPEN_NOFOLLOW    (1 << 3)
 #define SOS_FS_OPEN_DIRECTORY   (1 << 4) /* Incompatible with CREAT/TRUNC */
 #define SOS_FS_OPEN_SYNC        (1 << 5)
 #define SOS_FS_OPEN_CLOSEONEXEC (1 << 6) /* By default, files are kept
                                             open upon an exec() */
 
 #define SOS_FS_OPEN_READ        (1 << 16)
 #define SOS_FS_OPEN_WRITE       (1 << 17)
 
 
 /**
  * FS access rights
  */
 #define SOS_FS_S_IRUSR   00400
 #define SOS_FS_S_IWUSR   00200
 #define SOS_FS_S_IXUSR   00100
 
 #define SOS_FS_S_IRWXALL 07777 /* For symlinks */
 
 sos_ret_t sos_fs_open(const struct sos_process *owner,
                       const char *_path,
                       sos_size_t _pathlen,
                       sos_ui32_t open_flags,
                       sos_ui32_t creat_access_rights,
                       struct sos_fs_opened_file ** of);
 
 sos_ret_t sos_fs_close(struct sos_fs_opened_file * of);
 
 sos_ret_t sos_fs_read(struct sos_fs_opened_file * of,
                       sos_uaddr_t dest_buf,
                       sos_size_t * /* in/ou */len);
 
 sos_ret_t sos_fs_readdir(struct sos_fs_opened_file * of,
                          struct sos_fs_dirent * result);
 
 sos_ret_t sos_fs_write(struct sos_fs_opened_file * of,
                        sos_uaddr_t src_buf,
                        sos_size_t * /* in/out */len);
 
 sos_ret_t sos_fs_seek(struct sos_fs_opened_file *of,
                       sos_lsoffset_t offset,
                       sos_seek_whence_t whence,
                       sos_lsoffset_t * result_position);
 
 sos_ret_t sos_fs_ftruncate(struct sos_fs_opened_file *of,
                            sos_lsoffset_t length);
 
 sos_ret_t sos_fs_mmap(struct sos_fs_opened_file *of,
                       sos_uaddr_t *uaddr, sos_size_t size,
                       sos_ui32_t access_rights,
                       sos_ui32_t flags,
                       sos_luoffset_t offset);
 
 sos_ret_t sos_fs_fsync(struct sos_fs_opened_file * of);
 
 sos_ret_t sos_fs_fcntl(struct sos_fs_opened_file *of,
                        int req_id,
                        sos_ui32_t req_arg /* Usually: sos_uaddr_t */);
 
 sos_ret_t sos_fs_ioctl(struct sos_fs_opened_file *of,
                        int req_id,
                        sos_ui32_t req_arg /* Usually: sos_uaddr_t */);
 
 sos_ret_t sos_fs_creat(const struct sos_process * creator,
                        const char * _path,
                        sos_size_t _pathlen,
                        sos_ui32_t access_rights);
 
 sos_ret_t sos_fs_link(const struct sos_process * creator,
                       const char * _old_path,
                       sos_size_t _old_pathlen,
                       const char * _dest_path,
                       sos_size_t _dest_pathlen);
 
 sos_ret_t sos_fs_rename(const struct sos_process * creator,
                         const char * _old_path,
                         sos_size_t _old_pathlen,
                         const char * _dest_path,
                         sos_size_t _dest_pathlen);
 
 sos_ret_t sos_fs_unlink(const struct sos_process * actor,
                         const char * _path,
                         sos_size_t _pathlen);
 
 sos_ret_t sos_fs_symlink(const struct sos_process * creator,
                          const char * _path,
                          sos_size_t _pathlen,
                          sos_uaddr_t symlink_target,
                          sos_size_t symlink_target_len);
 
 sos_ret_t sos_fs_mknod(const struct sos_process * creator,
                        const char * _path,
                        sos_size_t _pathlen,
                        sos_fs_node_type_t type /* only block/char allowed */,
                        sos_ui32_t access_rights,
                        const struct sos_fs_dev_id_t * devid);
 
 sos_ret_t sos_fs_mkdir(const struct sos_process * creator,
                        const char * _path,
                        sos_size_t _pathlen,
                        sos_ui32_t access_rights);
 
 sos_ret_t sos_fs_rmdir(const struct sos_process * actor,
                        const char * _path,
                        sos_size_t _pathlen);
 
 sos_ret_t sos_fs_chmod(const struct sos_process * actor,
                        const char * _path,
                        sos_size_t _pathlen,
                        sos_ui32_t access_rights);
 
 sos_ret_t sos_fs_stat(const struct sos_process * actor,
                       const char * _path,
                       sos_size_t _pathlen,
                       int nofollow,
                       struct sos_fs_stat * result);
 
 
 /* ***************************************************************
  * Restricted functions reserved to FS code and block/char devices
  */
 
 /**
  * Function to be called when proposing a new File system type
  */
 sos_ret_t sos_fs_register_fs_type(struct sos_fs_manager_type * fstype);
 sos_ret_t sos_fs_unregister_fs_type(struct sos_fs_manager_type * fstype);
 
 /**
  * Marthe given file as dirty, for FS supporting deferred write access
  * mode
  */
 sos_ret_t sos_fs_mark_dirty(struct sos_fs_opened_file * of);
 
 /**
  * Helper function to be called from the mount() method of the FS
  * instance code. Responsible for creating and updating the "root"
  * field of the FS instance structure and for connecting this FS in
  * the nscache
  * @param root_fsnode The root of the FS being mounted
  */
 sos_ret_t sos_fs_register_fs_instance(struct sos_fs_manager_instance * fs,
                                       struct sos_fs_node * root_fsnode);
 
 /**
  * Helper function to be called from the umount() method of the FS
  * instance code. Responsible for unregistering the instance from the
  * FS type's instances list and for disconnecting this mountpoint in
  * the nscache.
  */
 sos_ret_t sos_fs_unregister_fs_instance(struct sos_fs_manager_instance * fs);
 
 
 /* ***************************************************************
  * Restricted functions reserved to syscall.c
  */
 sos_ret_t sos_fs_ref_opened_file(struct sos_fs_opened_file * of);
 sos_ret_t _sos_fs_unref_opened_file(struct sos_fs_opened_file ** of);
 #define sos_fs_unref_opened_file(f) _sos_fs_unref_opened_file(&(f))
 
 
 /* ***************************************************************
  * Restricted functions to be used only by fs_nscache.c
  */
 
 sos_ret_t sos_fs_ref_fsnode(struct sos_fs_node * fsnode);
 
 sos_ret_t _sos_fs_unref_fsnode(struct sos_fs_node * fsnode);
 #define sos_fs_unref_fsnode(n) \
   ({ sos_ret_t __retval = _sos_fs_unref_fsnode(n); (n)=NULL; __retval; })
 
 
 /* ***************************************************************
  * Restricted functions reserved to process.c and main.c:start_init()
  */
 sos_ret_t sos_fs_new_opened_file(const struct sos_process * proc,
                                  struct sos_fs_nscache_node * nsnode,
                                  sos_ui32_t open_flags,
                                  struct sos_fs_opened_file ** result_of);
 
 
 sos_ret_t sos_fs_duplicate_opened_file(struct sos_fs_opened_file * src_of,
                                        const struct sos_process * dst_proc,
                                        struct sos_fs_opened_file ** result_of);
 
 
 
 #endif /* _SOS_FS_H_ */