path: root/doc/filesystem/mounting.t

@c
@c  COPYRIGHT (c) 1988-1998.
@c  On-Line Applications Research Corporation (OAR).
@c  All rights reserved.
@c
@c  $Id$
@c

@chapter Mounting and Unmounting Filesystems

@section Mount Points

The following is the list of the characteristics of a mount point:

@itemize @bullet

@item The mount point must be a directory. It may have files and other
directories under it. These files and directories will be hidden when the
file system is mounted.

@item The task must have read/write/execute permissions to the mount point
or the mount attempt will be rejected.

@item Only one file system can be mounted to a single mount point.

@item The Root of the mountable file system will be referenced by the name
of the mount point after the mount is complete.

@end itemize

@section Mount Table Chain

Each entry in the mount table chain is of the following type:

@example
struct rtems_filesystem_mount_table_entry_tt
@{
   Chain_Node                             Node;
   rtems_filesystem_location_info_t       mt_point_node;
   rtems_filesystem_location_info_t       mt_fs_root;
   int                                    options;
   void                                  *fs_info;

   rtems_filesystem_limits_and_options_t  pathconf_limits_and_options;

  /*
   *  When someone adds a mounted filesystem on a real device,
   *  this will need to be used.
   *
   *  The best option long term for this is probably an
   *  open file descriptor.
   */
   char                                  *dev;
@};
@end example

@section Adding entries to the chain during mount

When a file system is mounted, its presence and location in the file
system hierarchy is recorded in a dynamic list structure known as a chain.
A unique rtems_filesystem_mount_table_entry_tt structure is logged for
each file system that is mounted. This includes the base file system.

@section Removing entries from the chain during unmount

When a file system is dismounted its entry in the mount table chain is
extracted and the memory for this entry is freed.