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-Read/Write HPFS 2.09
-1998-2004, Mikulas Patocka
-
-email: mikulas@artax.karlin.mff.cuni.cz
-homepage: http://artax.karlin.mff.cuni.cz/~mikulas/vyplody/hpfs/index-e.cgi
-
-CREDITS:
-Chris Smith, 1993, original read-only HPFS, some code and hpfs structures file
- is taken from it
-Jacques Gelinas, MSDos mmap, Inspired by fs/nfs/mmap.c (Jon Tombs 15 Aug 1993)
-Werner Almesberger, 1992, 1993, MSDos option parser & CR/LF conversion
-
-Mount options
-
-uid=xxx,gid=xxx,umask=xxx (default uid=gid=0 umask=default_system_umask)
- Set owner/group/mode for files that do not have it specified in extended
- attributes. Mode is inverted umask - for example umask 027 gives owner
- all permission, group read permission and anybody else no access. Note
- that for files mode is anded with 0666. If you want files to have 'x'
- rights, you must use extended attributes.
-case=lower,asis (default asis)
- File name lowercasing in readdir.
-conv=binary,text,auto (default binary)
- CR/LF -> LF conversion, if auto, decision is made according to extension
- - there is a list of text extensions (I thing it's better to not convert
- text file than to damage binary file). If you want to change that list,
- change it in the source. Original readonly HPFS contained some strange
- heuristic algorithm that I removed. I thing it's danger to let the
- computer decide whether file is text or binary. For example, DJGPP
- binaries contain small text message at the beginning and they could be
- misidentified and damaged under some circumstances.
-check=none,normal,strict (default normal)
- Check level. Selecting none will cause only little speedup and big
- danger. I tried to write it so that it won't crash if check=normal on
- corrupted filesystems. check=strict means many superfluous checks -
- used for debugging (for example it checks if file is allocated in
- bitmaps when accessing it).
-errors=continue,remount-ro,panic (default remount-ro)
- Behaviour when filesystem errors found.
-chkdsk=no,errors,always (default errors)
- When to mark filesystem dirty so that OS/2 checks it.
-eas=no,ro,rw (default rw)
- What to do with extended attributes. 'no' - ignore them and use always
- values specified in uid/gid/mode options. 'ro' - read extended
- attributes but do not create them. 'rw' - create extended attributes
- when you use chmod/chown/chgrp/mknod/ln -s on the filesystem.
-timeshift=(-)nnn (default 0)
- Shifts the time by nnn seconds. For example, if you see under linux
- one hour more, than under os/2, use timeshift=-3600.
-
-
-File names
-
-As in OS/2, filenames are case insensitive. However, shell thinks that names
-are case sensitive, so for example when you create a file FOO, you can use
-'cat FOO', 'cat Foo', 'cat foo' or 'cat F*' but not 'cat f*'. Note, that you
-also won't be able to compile linux kernel (and maybe other things) on HPFS
-because kernel creates different files with names like bootsect.S and
-bootsect.s. When searching for file thats name has characters >= 128, codepages
-are used - see below.
-OS/2 ignores dots and spaces at the end of file name, so this driver does as
-well. If you create 'a. ...', the file 'a' will be created, but you can still
-access it under names 'a.', 'a..', 'a . . . ' etc.
-
-
-Extended attributes
-
-On HPFS partitions, OS/2 can associate to each file a special information called
-extended attributes. Extended attributes are pairs of (key,value) where key is
-an ascii string identifying that attribute and value is any string of bytes of
-variable length. OS/2 stores window and icon positions and file types there. So
-why not use it for unix-specific info like file owner or access rights? This
-driver can do it. If you chown/chgrp/chmod on a hpfs partition, extended
-attributes with keys "UID", "GID" or "MODE" and 2-byte values are created. Only
-that extended attributes those value differs from defaults specified in mount
-options are created. Once created, the extended attributes are never deleted,
-they're just changed. It means that when your default uid=0 and you type
-something like 'chown luser file; chown root file' the file will contain
-extended attribute UID=0. And when you umount the fs and mount it again with
-uid=luser_uid, the file will be still owned by root! If you chmod file to 444,
-extended attribute "MODE" will not be set, this special case is done by setting
-read-only flag. When you mknod a block or char device, besides "MODE", the
-special 4-byte extended attribute "DEV" will be created containing the device
-number. Currently this driver cannot resize extended attributes - it means
-that if somebody (I don't know who?) has set "UID", "GID", "MODE" or "DEV"
-attributes with different sizes, they won't be rewritten and changing these
-values doesn't work.
-
-
-Symlinks
-
-You can do symlinks on HPFS partition, symlinks are achieved by setting extended
-attribute named "SYMLINK" with symlink value. Like on ext2, you can chown and
-chgrp symlinks but I don't know what is it good for. chmoding symlink results
-in chmoding file where symlink points. These symlinks are just for Linux use and
-incompatible with OS/2. OS/2 PmShell symlinks are not supported because they are
-stored in very crazy way. They tried to do it so that link changes when file is
-moved ... sometimes it works. But the link is partly stored in directory
-extended attributes and partly in OS2SYS.INI. I don't want (and don't know how)
-to analyze or change OS2SYS.INI.
-
-
-Codepages
-
-HPFS can contain several uppercasing tables for several codepages and each
-file has a pointer to codepage its name is in. However OS/2 was created in
-America where people don't care much about codepages and so multiple codepages
-support is quite buggy. I have Czech OS/2 working in codepage 852 on my disk.
-Once I booted English OS/2 working in cp 850 and I created a file on my 852
-partition. It marked file name codepage as 850 - good. But when I again booted
-Czech OS/2, the file was completely inaccessible under any name. It seems that
-OS/2 uppercases the search pattern with its system code page (852) and file
-name it's comparing to with its code page (850). These could never match. Is it
-really what IBM developers wanted? But problems continued. When I created in
-Czech OS/2 another file in that directory, that file was inaccessible too. OS/2
-probably uses different uppercasing method when searching where to place a file
-(note, that files in HPFS directory must be sorted) and when searching for
-a file. Finally when I opened this directory in PmShell, PmShell crashed (the
-funny thing was that, when rebooted, PmShell tried to reopen this directory
-again :-). chkdsk happily ignores these errors and only low-level disk
-modification saved me. Never mix different language versions of OS/2 on one
-system although HPFS was designed to allow that.
-OK, I could implement complex codepage support to this driver but I think it
-would cause more problems than benefit with such buggy implementation in OS/2.
-So this driver simply uses first codepage it finds for uppercasing and
-lowercasing no matter what's file codepage index. Usually all file names are in
-this codepage - if you don't try to do what I described above :-)
-
-
-Known bugs
-
-HPFS386 on OS/2 server is not supported. HPFS386 installed on normal OS/2 client
-should work. If you have OS/2 server, use only read-only mode. I don't know how
-to handle some HPFS386 structures like access control list or extended perm
-list, I don't know how to delete them when file is deleted and how to not
-overwrite them with extended attributes. Send me some info on these structures
-and I'll make it. However, this driver should detect presence of HPFS386
-structures, remount read-only and not destroy them (I hope).
-
-When there's not enough space for extended attributes, they will be truncated
-and no error is returned.
-
-OS/2 can't access files if the path is longer than about 256 chars but this
-driver allows you to do it. chkdsk ignores such errors.
-
-Sometimes you won't be able to delete some files on a very full filesystem
-(returning error ENOSPC). That's because file in non-leaf node in directory tree
-(one directory, if it's large, has dirents in tree on HPFS) must be replaced
-with another node when deleted. And that new file might have larger name than
-the old one so the new name doesn't fit in directory node (dnode). And that
-would result in directory tree splitting, that takes disk space. Workaround is
-to delete other files that are leaf (probability that the file is non-leaf is
-about 1/50) or to truncate file first to make some space.
-You encounter this problem only if you have many directories so that
-preallocated directory band is full i.e.
- number_of_directories / size_of_filesystem_in_mb > 4.
-
-You can't delete open directories.
-
-You can't rename over directories (what is it good for?).
-
-Renaming files so that only case changes doesn't work. This driver supports it
-but vfs doesn't. Something like 'mv file FILE' won't work.
-
-All atimes and directory mtimes are not updated. That's because of performance
-reasons. If you extremely wish to update them, let me know, I'll write it (but
-it will be slow).
-
-When the system is out of memory and swap, it may slightly corrupt filesystem
-(lost files, unbalanced directories). (I guess all filesystem may do it).
-
-When compiled, you get warning: function declaration isn't a prototype. Does
-anybody know what does it mean?
-
-
-What does "unbalanced tree" message mean?
-
-Old versions of this driver created sometimes unbalanced dnode trees. OS/2
-chkdsk doesn't scream if the tree is unbalanced (and sometimes creates
-unbalanced trees too :-) but both HPFS and HPFS386 contain bug that it rarely
-crashes when the tree is not balanced. This driver handles unbalanced trees
-correctly and writes warning if it finds them. If you see this message, this is
-probably because of directories created with old version of this driver.
-Workaround is to move all files from that directory to another and then back
-again. Do it in Linux, not OS/2! If you see this message in directory that is
-whole created by this driver, it is BUG - let me know about it.
-
-
-Bugs in OS/2
-
-When you have two (or more) lost directories pointing each to other, chkdsk
-locks up when repairing filesystem.
-
-Sometimes (I think it's random) when you create a file with one-char name under
-OS/2, OS/2 marks it as 'long'. chkdsk then removes this flag saying "Minor fs
-error corrected".
-
-File names like "a .b" are marked as 'long' by OS/2 but chkdsk "corrects" it and
-marks them as short (and writes "minor fs error corrected"). This bug is not in
-HPFS386.
-
-Codepage bugs described above.
-
-If you don't install fixpacks, there are many, many more...
-
-
-History
-
-0.90 First public release
-0.91 Fixed bug that caused shooting to memory when write_inode was called on
- open inode (rarely happened)
-0.92 Fixed a little memory leak in freeing directory inodes
-0.93 Fixed bug that locked up the machine when there were too many filenames
- with first 15 characters same
- Fixed write_file to zero file when writing behind file end
-0.94 Fixed a little memory leak when trying to delete busy file or directory
-0.95 Fixed a bug that i_hpfs_parent_dir was not updated when moving files
-1.90 First version for 2.1.1xx kernels
-1.91 Fixed a bug that chk_sectors failed when sectors were at the end of disk
- Fixed a race-condition when write_inode is called while deleting file
- Fixed a bug that could possibly happen (with very low probability) when
- using 0xff in filenames
- Rewritten locking to avoid race-conditions
- Mount option 'eas' now works
- Fsync no longer returns error
- Files beginning with '.' are marked hidden
- Remount support added
- Alloc is not so slow when filesystem becomes full
- Atimes are no more updated because it slows down operation
- Code cleanup (removed all commented debug prints)
-1.92 Corrected a bug when sync was called just before closing file
-1.93 Modified, so that it works with kernels >= 2.1.131, I don't know if it
- works with previous versions
- Fixed a possible problem with disks > 64G (but I don't have one, so I can't
- test it)
- Fixed a file overflow at 2G
- Added new option 'timeshift'
- Changed behaviour on HPFS386: It is now possible to operate on HPFS386 in
- read-only mode
- Fixed a bug that slowed down alloc and prevented allocating 100% space
- (this bug was not destructive)
-1.94 Added workaround for one bug in Linux
- Fixed one buffer leak
- Fixed some incompatibilities with large extended attributes (but it's still
- not 100% ok, I have no info on it and OS/2 doesn't want to create them)
- Rewritten allocation
- Fixed a bug with i_blocks (du sometimes didn't display correct values)
- Directories have no longer archive attribute set (some programs don't like
- it)
- Fixed a bug that it set badly one flag in large anode tree (it was not
- destructive)
-1.95 Fixed one buffer leak, that could happen on corrupted filesystem
- Fixed one bug in allocation in 1.94
-1.96 Added workaround for one bug in OS/2 (HPFS locked up, HPFS386 reported
- error sometimes when opening directories in PMSHELL)
- Fixed a possible bitmap race
- Fixed possible problem on large disks
- You can now delete open files
- Fixed a nondestructive race in rename
-1.97 Support for HPFS v3 (on large partitions)
- Fixed a bug that it didn't allow creation of files > 128M (it should be 2G)
-1.97.1 Changed names of global symbols
- Fixed a bug when chmoding or chowning root directory
-1.98 Fixed a deadlock when using old_readdir
- Better directory handling; workaround for "unbalanced tree" bug in OS/2
-1.99 Corrected a possible problem when there's not enough space while deleting
- file
- Now it tries to truncate the file if there's not enough space when deleting
- Removed a lot of redundant code
-2.00 Fixed a bug in rename (it was there since 1.96)
- Better anti-fragmentation strategy
-2.01 Fixed problem with directory listing over NFS
- Directory lseek now checks for proper parameters
- Fixed race-condition in buffer code - it is in all filesystems in Linux;
- when reading device (cat /dev/hda) while creating files on it, files
- could be damaged
-2.02 Workaround for bug in breada in Linux. breada could cause accesses beyond
- end of partition
-2.03 Char, block devices and pipes are correctly created
- Fixed non-crashing race in unlink (Alexander Viro)
- Now it works with Japanese version of OS/2
-2.04 Fixed error when ftruncate used to extend file
-2.05 Fixed crash when got mount parameters without =
- Fixed crash when allocation of anode failed due to full disk
- Fixed some crashes when block io or inode allocation failed
-2.06 Fixed some crash on corrupted disk structures
- Better allocation strategy
- Reschedule points added so that it doesn't lock CPU long time
- It should work in read-only mode on Warp Server
-2.07 More fixes for Warp Server. Now it really works
-2.08 Creating new files is not so slow on large disks
- An attempt to sync deleted file does not generate filesystem error
-2.09 Fixed error on extremely fragmented files
-
-
- vim: set textwidth=80: