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Diffstat (limited to 'kernel/Documentation/filesystems/hpfs.txt')
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diff --git a/kernel/Documentation/filesystems/hpfs.txt b/kernel/Documentation/filesystems/hpfs.txt new file mode 100644 index 000000000..74630bd50 --- /dev/null +++ b/kernel/Documentation/filesystems/hpfs.txt @@ -0,0 +1,296 @@ +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: |