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Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.

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 its 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 Workaround 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 extremely fragmented files
296	 vim: set textwidth=80:
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