root/morphix/trunk/mini_fo/README.mini_fo

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Initial import, branching from morphix svn

Line 
1 Little README for the mini_fo overlay filesystem.
2
3 Compiling:
4
5         The new mini_fo overlay filesystem currently works only for 2.6
6         kernels, 2.4 is no more supported.
7
8         Edit the Makefile and adjust the location of the kernel
9         headers. If cross compiling set $CROSS_COMPILE.
10
11         "make" compiles the module.
12
13 Using:
14         There are three scripts to do the work (only tqm860l)
15
16               lmod will do an "insmod -m <module>" what creates the mapfile,
17               which is needed for debugging later.
18
19               mount_hda will mount two hard disk partitions hda2 and
20               hda3 onto /mnt/base respectively /mnt/storage .
21
22               load will actually mount the overlay filesystem, using
23               the two hard disk partitions as base and storage
24               filesystems.
25
26               The do_all script will perform the three steps from
27               above.
28
29
30         The module should work plattform independently with different
31         filesystem types for base and storage.
32         WARNING: Do not export a mounted overlay filesystem via NFS. This
33         will cause unpredictable results.
34
35         The general mount syntax is:
36
37         mount -t mini_fo -o dir=<base directory>\
38                             dir2=<storage directory>\
39                             <base directory> <mount directory>
40
41         You can turn on the debugging messages by passing the option
42         ",debug=N" after the dir2 option, where N is the debug level
43         ranging from 1 (little information) to 18 (a lot of
44         information). Check print.c for details.
45
46         Alternatively the debug level can be set using fist_ioctl:
47
48         turn off all debugging: fist_ioctl -d <mount dir> 0
49         turn on all debugging:  fist_ioctl -d <mount dir> 18
50
51         Its worth mentioning that the debug messages are not always
52         usefull and normally its better to keep them turned off
53         (which is default).
54
55
56 Files:
57
58         The most interesting files concerning the overlay behaviour
59         are:
60
61         main.c:
62         contains the mini_fo_read_super funtions for reading
63         the superblock, mini_fo_[tri]_interpose for interposing inodes
64         and the parse_options that parses the mount options.
65
66         file.c:
67         contains the file operations like mini_fo_read,
68         mini_fo_open and mini_fo_readdir.
69
70         inode.c:
71         contains the inodes operations like the important
72         mini_fo_lookup function called by "ls".
73
74         dentry.c:
75         The dentry operations.
76
77         super.c:
78         The super operations.
79
80         mini_fo:
81         important definitions of structures like the private
82         data structures for mini_fo objects Macros to access them.
83
84         aux.c:
85         Contains a lot of helper functions used by the overlay fs, like
86         the build_sto_structure function, the wol and ndl - list
87         functions and more.
88
89
90 Other information:
91
92         General Overview of the VFS in
93         Documentation/filesystems/vfs.txt
94
95         VFS Kernel API:
96         http://kernelnewbies.org/documents/kdoc/kernel-api/vfs.html
97
98
99 Copyright (C) 2004 Markus Klotzbuecher <mk@creamnet.de>
100 new implementation by Olivier Evalet  <evaleto at programmers.ch>
101
102 This program is free software; you can redistribute it and/or
103 modify it under the terms of the GNU General Public License
104 as published by the Free Software Foundation; either version
105 2 of the License, or (at your option) any later version.
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