view Documentation/filesystems/hpfs.txt @ 524:7f8b544237bf

netfront: Allow netfront in domain 0.

This is useful if your physical network device is in a utility domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Apr 15 15:18:58 2008 +0100 (2008-04-15)
parents 831230e53067
line source
1 Read/Write HPFS 2.09
2 1998-2004, Mikulas Patocka
4 email: mikulas@artax.karlin.mff.cuni.cz
5 homepage: http://artax.karlin.mff.cuni.cz/~mikulas/vyplody/hpfs/index-e.cgi
8 Chris Smith, 1993, original read-only HPFS, some code and hpfs structures file
9 is taken from it
10 Jacques Gelinas, MSDos mmap, Inspired by fs/nfs/mmap.c (Jon Tombs 15 Aug 1993)
11 Werner Almesberger, 1992, 1993, MSDos option parser & CR/LF conversion
13 Mount options
15 uid=xxx,gid=xxx,umask=xxx (default uid=gid=0 umask=default_system_umask)
16 Set owner/group/mode for files that do not have it specified in extended
17 attributes. Mode is inverted umask - for example umask 027 gives owner
18 all permission, group read permission and anybody else no access. Note
19 that for files mode is anded with 0666. If you want files to have 'x'
20 rights, you must use extended attributes.
21 case=lower,asis (default asis)
22 File name lowercasing in readdir.
23 conv=binary,text,auto (default binary)
24 CR/LF -> LF conversion, if auto, decision is made according to extension
25 - there is a list of text extensions (I thing it's better to not convert
26 text file than to damage binary file). If you want to change that list,
27 change it in the source. Original readonly HPFS contained some strange
28 heuristic algorithm that I removed. I thing it's danger to let the
29 computer decide whether file is text or binary. For example, DJGPP
30 binaries contain small text message at the beginning and they could be
31 misidentified and damaged under some circumstances.
32 check=none,normal,strict (default normal)
33 Check level. Selecting none will cause only little speedup and big
34 danger. I tried to write it so that it won't crash if check=normal on
35 corrupted filesystems. check=strict means many superfluous checks -
36 used for debugging (for example it checks if file is allocated in
37 bitmaps when accessing it).
38 errors=continue,remount-ro,panic (default remount-ro)
39 Behaviour when filesystem errors found.
40 chkdsk=no,errors,always (default errors)
41 When to mark filesystem dirty so that OS/2 checks it.
42 eas=no,ro,rw (default rw)
43 What to do with extended attributes. 'no' - ignore them and use always
44 values specified in uid/gid/mode options. 'ro' - read extended
45 attributes but do not create them. 'rw' - create extended attributes
46 when you use chmod/chown/chgrp/mknod/ln -s on the filesystem.
47 timeshift=(-)nnn (default 0)
48 Shifts the time by nnn seconds. For example, if you see under linux
49 one hour more, than under os/2, use timeshift=-3600.
52 File names
54 As in OS/2, filenames are case insensitive. However, shell thinks that names
55 are case sensitive, so for example when you create a file FOO, you can use
56 'cat FOO', 'cat Foo', 'cat foo' or 'cat F*' but not 'cat f*'. Note, that you
57 also won't be able to compile linux kernel (and maybe other things) on HPFS
58 because kernel creates different files with names like bootsect.S and
59 bootsect.s. When searching for file thats name has characters >= 128, codepages
60 are used - see below.
61 OS/2 ignores dots and spaces at the end of file name, so this driver does as
62 well. If you create 'a. ...', the file 'a' will be created, but you can still
63 access it under names 'a.', 'a..', 'a . . . ' etc.
66 Extended attributes
68 On HPFS partitions, OS/2 can associate to each file a special information called
69 extended attributes. Extended attributes are pairs of (key,value) where key is
70 an ascii string identifying that attribute and value is any string of bytes of
71 variable length. OS/2 stores window and icon positions and file types there. So
72 why not use it for unix-specific info like file owner or access rights? This
73 driver can do it. If you chown/chgrp/chmod on a hpfs partition, extended
74 attributes with keys "UID", "GID" or "MODE" and 2-byte values are created. Only
75 that extended attributes those value differs from defaults specified in mount
76 options are created. Once created, the extended attributes are never deleted,
77 they're just changed. It means that when your default uid=0 and you type
78 something like 'chown luser file; chown root file' the file will contain
79 extended attribute UID=0. And when you umount the fs and mount it again with
80 uid=luser_uid, the file will be still owned by root! If you chmod file to 444,
81 extended attribute "MODE" will not be set, this special case is done by setting
82 read-only flag. When you mknod a block or char device, besides "MODE", the
83 special 4-byte extended attribute "DEV" will be created containing the device
84 number. Currently this driver cannot resize extended attributes - it means
85 that if somebody (I don't know who?) has set "UID", "GID", "MODE" or "DEV"
86 attributes with different sizes, they won't be rewritten and changing these
87 values doesn't work.
90 Symlinks
92 You can do symlinks on HPFS partition, symlinks are achieved by setting extended
93 attribute named "SYMLINK" with symlink value. Like on ext2, you can chown and
94 chgrp symlinks but I don't know what is it good for. chmoding symlink results
95 in chmoding file where symlink points. These symlinks are just for Linux use and
96 incompatible with OS/2. OS/2 PmShell symlinks are not supported because they are
97 stored in very crazy way. They tried to do it so that link changes when file is
98 moved ... sometimes it works. But the link is partly stored in directory
99 extended attributes and partly in OS2SYS.INI. I don't want (and don't know how)
100 to analyze or change OS2SYS.INI.
103 Codepages
105 HPFS can contain several uppercasing tables for several codepages and each
106 file has a pointer to codepage it's name is in. However OS/2 was created in
107 America where people don't care much about codepages and so multiple codepages
108 support is quite buggy. I have Czech OS/2 working in codepage 852 on my disk.
109 Once I booted English OS/2 working in cp 850 and I created a file on my 852
110 partition. It marked file name codepage as 850 - good. But when I again booted
111 Czech OS/2, the file was completely inaccessible under any name. It seems that
112 OS/2 uppercases the search pattern with its system code page (852) and file
113 name it's comparing to with its code page (850). These could never match. Is it
114 really what IBM developers wanted? But problems continued. When I created in
115 Czech OS/2 another file in that directory, that file was inaccessible too. OS/2
116 probably uses different uppercasing method when searching where to place a file
117 (note, that files in HPFS directory must be sorted) and when searching for
118 a file. Finally when I opened this directory in PmShell, PmShell crashed (the
119 funny thing was that, when rebooted, PmShell tried to reopen this directory
120 again :-). chkdsk happily ignores these errors and only low-level disk
121 modification saved me. Never mix different language versions of OS/2 on one
122 system although HPFS was designed to allow that.
123 OK, I could implement complex codepage support to this driver but I think it
124 would cause more problems than benefit with such buggy implementation in OS/2.
125 So this driver simply uses first codepage it finds for uppercasing and
126 lowercasing no matter what's file codepage index. Usually all file names are in
127 this codepage - if you don't try to do what I described above :-)
130 Known bugs
132 HPFS386 on OS/2 server is not supported. HPFS386 installed on normal OS/2 client
133 should work. If you have OS/2 server, use only read-only mode. I don't know how
134 to handle some HPFS386 structures like access control list or extended perm
135 list, I don't know how to delete them when file is deleted and how to not
136 overwrite them with extended attributes. Send me some info on these structures
137 and I'll make it. However, this driver should detect presence of HPFS386
138 structures, remount read-only and not destroy them (I hope).
140 When there's not enough space for extended attributes, they will be truncated
141 and no error is returned.
143 OS/2 can't access files if the path is longer than about 256 chars but this
144 driver allows you to do it. chkdsk ignores such errors.
146 Sometimes you won't be able to delete some files on a very full filesystem
147 (returning error ENOSPC). That's because file in non-leaf node in directory tree
148 (one directory, if it's large, has dirents in tree on HPFS) must be replaced
149 with another node when deleted. And that new file might have larger name than
150 the old one so the new name doesn't fit in directory node (dnode). And that
151 would result in directory tree splitting, that takes disk space. Workaround is
152 to delete other files that are leaf (probability that the file is non-leaf is
153 about 1/50) or to truncate file first to make some space.
154 You encounter this problem only if you have many directories so that
155 preallocated directory band is full i.e.
156 number_of_directories / size_of_filesystem_in_mb > 4.
158 You can't delete open directories.
160 You can't rename over directories (what is it good for?).
162 Renaming files so that only case changes doesn't work. This driver supports it
163 but vfs doesn't. Something like 'mv file FILE' won't work.
165 All atimes and directory mtimes are not updated. That's because of performance
166 reasons. If you extremely wish to update them, let me know, I'll write it (but
167 it will be slow).
169 When the system is out of memory and swap, it may slightly corrupt filesystem
170 (lost files, unbalanced directories). (I guess all filesystem may do it).
172 When compiled, you get warning: function declaration isn't a prototype. Does
173 anybody know what does it mean?
176 What does "unbalanced tree" message mean?
178 Old versions of this driver created sometimes unbalanced dnode trees. OS/2
179 chkdsk doesn't scream if the tree is unbalanced (and sometimes creates
180 unbalanced trees too :-) but both HPFS and HPFS386 contain bug that it rarely
181 crashes when the tree is not balanced. This driver handles unbalanced trees
182 correctly and writes warning if it finds them. If you see this message, this is
183 probably because of directories created with old version of this driver.
184 Workaround is to move all files from that directory to another and then back
185 again. Do it in Linux, not OS/2! If you see this message in directory that is
186 whole created by this driver, it is BUG - let me know about it.
189 Bugs in OS/2
191 When you have two (or more) lost directories pointing each to other, chkdsk
192 locks up when repairing filesystem.
194 Sometimes (I think it's random) when you create a file with one-char name under
195 OS/2, OS/2 marks it as 'long'. chkdsk then removes this flag saying "Minor fs
196 error corrected".
198 File names like "a .b" are marked as 'long' by OS/2 but chkdsk "corrects" it and
199 marks them as short (and writes "minor fs error corrected"). This bug is not in
200 HPFS386.
202 Codepage bugs described above.
204 If you don't install fixpacks, there are many, many more...
207 History
209 0.90 First public release
210 0.91 Fixed bug that caused shooting to memory when write_inode was called on
211 open inode (rarely happened)
212 0.92 Fixed a little memory leak in freeing directory inodes
213 0.93 Fixed bug that locked up the machine when there were too many filenames
214 with first 15 characters same
215 Fixed write_file to zero file when writing behind file end
216 0.94 Fixed a little memory leak when trying to delete busy file or directory
217 0.95 Fixed a bug that i_hpfs_parent_dir was not updated when moving files
218 1.90 First version for 2.1.1xx kernels
219 1.91 Fixed a bug that chk_sectors failed when sectors were at the end of disk
220 Fixed a race-condition when write_inode is called while deleting file
221 Fixed a bug that could possibly happen (with very low probability) when
222 using 0xff in filenames
223 Rewritten locking to avoid race-conditions
224 Mount option 'eas' now works
225 Fsync no longer returns error
226 Files beginning with '.' are marked hidden
227 Remount support added
228 Alloc is not so slow when filesystem becomes full
229 Atimes are no more updated because it slows down operation
230 Code cleanup (removed all commented debug prints)
231 1.92 Corrected a bug when sync was called just before closing file
232 1.93 Modified, so that it works with kernels >= 2.1.131, I don't know if it
233 works with previous versions
234 Fixed a possible problem with disks > 64G (but I don't have one, so I can't
235 test it)
236 Fixed a file overflow at 2G
237 Added new option 'timeshift'
238 Changed behaviour on HPFS386: It is now possible to operate on HPFS386 in
239 read-only mode
240 Fixed a bug that slowed down alloc and prevented allocating 100% space
241 (this bug was not destructive)
242 1.94 Added workaround for one bug in Linux
243 Fixed one buffer leak
244 Fixed some incompatibilities with large extended attributes (but it's still
245 not 100% ok, I have no info on it and OS/2 doesn't want to create them)
246 Rewritten allocation
247 Fixed a bug with i_blocks (du sometimes didn't display correct values)
248 Directories have no longer archive attribute set (some programs don't like
249 it)
250 Fixed a bug that it set badly one flag in large anode tree (it was not
251 destructive)
252 1.95 Fixed one buffer leak, that could happen on corrupted filesystem
253 Fixed one bug in allocation in 1.94
254 1.96 Added workaround for one bug in OS/2 (HPFS locked up, HPFS386 reported
255 error sometimes when opening directories in PMSHELL)
256 Fixed a possible bitmap race
257 Fixed possible problem on large disks
258 You can now delete open files
259 Fixed a nondestructive race in rename
260 1.97 Support for HPFS v3 (on large partitions)
261 Fixed a bug that it didn't allow creation of files > 128M (it should be 2G)
262 1.97.1 Changed names of global symbols
263 Fixed a bug when chmoding or chowning root directory
264 1.98 Fixed a deadlock when using old_readdir
265 Better directory handling; workaround for "unbalanced tree" bug in OS/2
266 1.99 Corrected a possible problem when there's not enough space while deleting
267 file
268 Now it tries to truncate the file if there's not enough space when deleting
269 Removed a lot of redundant code
270 2.00 Fixed a bug in rename (it was there since 1.96)
271 Better anti-fragmentation strategy
272 2.01 Fixed problem with directory listing over NFS
273 Directory lseek now checks for proper parameters
274 Fixed race-condition in buffer code - it is in all filesystems in Linux;
275 when reading device (cat /dev/hda) while creating files on it, files
276 could be damaged
277 2.02 Woraround for bug in breada in Linux. breada could cause accesses beyond
278 end of partition
279 2.03 Char, block devices and pipes are correctly created
280 Fixed non-crashing race in unlink (Alexander Viro)
281 Now it works with Japanese version of OS/2
282 2.04 Fixed error when ftruncate used to extend file
283 2.05 Fixed crash when got mount parameters without =
284 Fixed crash when allocation of anode failed due to full disk
285 Fixed some crashes when block io or inode allocation failed
286 2.06 Fixed some crash on corrupted disk structures
287 Better allocation strategy
288 Reschedule points added so that it doesn't lock CPU long time
289 It should work in read-only mode on Warp Server
290 2.07 More fixes for Warp Server. Now it really works
291 2.08 Creating new files is not so slow on large disks
292 An attempt to sync deleted file does not generate filesystem error
293 2.09 Fixed error on extremly fragmented files
296 vim: set textwidth=80: