Documentation/filesystems/hpfs.rst

1 .. SPDX-License-Identifier: GPL-2.0
7 1998-2004, Mikulas Patocka
10 :homepage: https://artax.karlin.mff.cuni.cz/~mikulas/vyplody/hpfs/index-e.cgi
14 Chris Smith, 1993, original read-only HPFS, some code and hpfs structures file
25 	attributes. Mode is inverted umask - for example umask 027 gives owner
27 	that for files mode is anded with 0666. If you want files to have 'x'
32 	CR/LF -> LF conversion, if auto, decision is made according to extension
33 	- there is a list of text extensions (I thing it's better to not convert
34 	text file than to damage binary file). If you want to change that list,
36 	heuristic algorithm that I removed. I thing it's danger to let the
42 	danger. I tried to write it so that it won't crash if check=normal on
43 	corrupted filesystems. check=strict means many superfluous checks -
46 errors=continue,remount-ro,panic (default remount-ro)
49 	When to mark filesystem dirty so that OS/2 checks it.
51 	What to do with extended attributes. 'no' - ignore them and use always
52 	values specified in uid/gid/mode options. 'ro' - read extended
53 	attributes but do not create them. 'rw' - create extended attributes
54 	when you use chmod/chown/chgrp/mknod/ln -s on the filesystem.
55 timeshift=(-)nnn (default 0)
57 	one hour more, than under os/2, use timeshift=-3600.
66 also won't be able to compile linux kernel (and maybe other things) on HPFS
69 are used - see below.
78 On HPFS partitions, OS/2 can associate to each file a special information called
82 why not use it for unix-specific info like file owner or access rights? This
84 attributes with keys "UID", "GID" or "MODE" and 2-byte values are created. Only
90 uid=luser_uid, the file will be still owned by root! If you chmod file to 444,
92 read-only flag. When you mknod a block or char device, besides "MODE", the
93 special 4-byte extended attribute "DEV" will be created containing the device
94 number. Currently this driver cannot resize extended attributes - it means
108 stored in very crazy way. They tried to do it so that link changes when file is
111 to analyze or change OS2SYS.INI.
118 file has a pointer to codepage its name is in. However OS/2 was created in
122 partition. It marked file name codepage as 850 - good. But when I again booted
125 name it's comparing to with its code page (850). These could never match. Is it
128 probably uses different uppercasing method when searching where to place a file
131 funny thing was that, when rebooted, PmShell tried to reopen this directory
132 again :-). chkdsk happily ignores these errors and only low-level disk
133 modification saved me.  Never mix different language versions of OS/2 on one
134 system although HPFS was designed to allow that.
135 OK, I could implement complex codepage support to this driver but I think it
139 this codepage - if you don't try to do what I described above :-)
146 should work. If you have OS/2 server, use only read-only mode. I don't know how
147 to handle some HPFS386 structures like access control list or extended perm
148 list, I don't know how to delete them when file is deleted and how to not
151 structures, remount read-only and not destroy them (I hope).
157 driver allows you to do it. chkdsk ignores such errors.
159 Sometimes you won't be able to delete some files on a very full filesystem
160 (returning error ENOSPC). That's because file in non-leaf node in directory tree
161 (one directory, if it's large, has dirents in tree on HPFS) must be replaced
163 the old one so the new name doesn't fit in directory node (dnode). And that
165 to delete other files that are leaf (probability that the file is non-leaf is
166 about 1/50) or to truncate file first to make some space.
167 You encounter this problem only if you have many directories so that
180 reasons. If you extremely wish to update them, let me know, I'll write it (but
195 unbalanced trees too :-) but both HPFS and HPFS386 contain bug that it rarely
199 Workaround is to move all files from that directory to another and then back
201 whole created by this driver, it is BUG - let me know about it.
207 When you have two (or more) lost directories pointing each to other, chkdsk
210 Sometimes (I think it's random) when you create a file with one-char name under
221 If you don't install fixpacks, there are many, many more...
229 0.91   Fixed bug that caused shooting to memory when write_inode was called on
232 0.93   Fixed bug that locked up the machine when there were too many filenames
234        Fixed write_file to zero file when writing behind file end
235 0.94   Fixed a little memory leak when trying to delete busy file or directory
239        Fixed a race-condition when write_inode is called while deleting file
243        Rewritten locking to avoid race-conditions
262        Fixed a possible problem with disks > 64G (but I don't have one, so I can't
269        Changed behaviour on HPFS386: It is now possible to operate on HPFS386 in
270        read-only mode
274 1.94   Added workaround for one bug in Linux
276        Fixed one buffer leak
279        not 100% ok, I have no info on it and OS/2 doesn't want to create them)
288        Fixed a bug that it set badly one flag in large anode tree (it was not
290 1.95   Fixed one buffer leak, that could happen on corrupted filesystem
292        Fixed one bug in allocation in 1.94
293 1.96   Added workaround for one bug in OS/2 (HPFS locked up, HPFS386 reported
315        Now it tries to truncate the file if there's not enough space when
320        Better anti-fragmentation strategy
325        Fixed race-condition in buffer code - it is in all filesystems in Linux;
332        Fixed non-crashing race in unlink (Alexander Viro)
335 2.04   Fixed error when ftruncate used to extend file
338        Fixed crash when allocation of anode failed due to full disk
347        It should work in read-only mode on Warp Server
351        An attempt to sync deleted file does not generate filesystem error