|
|
@@ -1,11 +1,8 @@
|
|
|
-This is the implementation of the SystemV/Coherent filesystem for Linux.
|
|
|
It implements all of
|
|
|
- Xenix FS,
|
|
|
- SystemV/386 FS,
|
|
|
- Coherent FS.
|
|
|
|
|
|
-This is version beta 4.
|
|
|
-
|
|
|
To install:
|
|
|
* Answer the 'System V and Coherent filesystem support' question with 'y'
|
|
|
when configuring the kernel.
|
|
|
@@ -28,11 +25,173 @@ Bugs in the present implementation:
|
|
|
for this FS on hard disk yet.
|
|
|
|
|
|
|
|
|
-Please report any bugs and suggestions to
|
|
|
- Bruno Haible <haible@ma2s2.mathematik.uni-karlsruhe.de>
|
|
|
- Pascal Haible <haible@izfm.uni-stuttgart.de>
|
|
|
- Krzysztof G. Baranowski <kgb@manjak.knm.org.pl>
|
|
|
+These filesystems are rather similar. Here is a comparison with Minix FS:
|
|
|
+
|
|
|
+* Linux fdisk reports on partitions
|
|
|
+ - Minix FS 0x81 Linux/Minix
|
|
|
+ - Xenix FS ??
|
|
|
+ - SystemV FS ??
|
|
|
+ - Coherent FS 0x08 AIX bootable
|
|
|
+
|
|
|
+* Size of a block or zone (data allocation unit on disk)
|
|
|
+ - Minix FS 1024
|
|
|
+ - Xenix FS 1024 (also 512 ??)
|
|
|
+ - SystemV FS 1024 (also 512 and 2048)
|
|
|
+ - Coherent FS 512
|
|
|
+
|
|
|
+* General layout: all have one boot block, one super block and
|
|
|
+ separate areas for inodes and for directories/data.
|
|
|
+ On SystemV Release 2 FS (e.g. Microport) the first track is reserved and
|
|
|
+ all the block numbers (including the super block) are offset by one track.
|
|
|
+
|
|
|
+* Byte ordering of "short" (16 bit entities) on disk:
|
|
|
+ - Minix FS little endian 0 1
|
|
|
+ - Xenix FS little endian 0 1
|
|
|
+ - SystemV FS little endian 0 1
|
|
|
+ - Coherent FS little endian 0 1
|
|
|
+ Of course, this affects only the file system, not the data of files on it!
|
|
|
+
|
|
|
+* Byte ordering of "long" (32 bit entities) on disk:
|
|
|
+ - Minix FS little endian 0 1 2 3
|
|
|
+ - Xenix FS little endian 0 1 2 3
|
|
|
+ - SystemV FS little endian 0 1 2 3
|
|
|
+ - Coherent FS PDP-11 2 3 0 1
|
|
|
+ Of course, this affects only the file system, not the data of files on it!
|
|
|
+
|
|
|
+* Inode on disk: "short", 0 means non-existent, the root dir ino is:
|
|
|
+ - Minix FS 1
|
|
|
+ - Xenix FS, SystemV FS, Coherent FS 2
|
|
|
+
|
|
|
+* Maximum number of hard links to a file:
|
|
|
+ - Minix FS 250
|
|
|
+ - Xenix FS ??
|
|
|
+ - SystemV FS ??
|
|
|
+ - Coherent FS >=10000
|
|
|
+
|
|
|
+* Free inode management:
|
|
|
+ - Minix FS a bitmap
|
|
|
+ - Xenix FS, SystemV FS, Coherent FS
|
|
|
+ There is a cache of a certain number of free inodes in the super-block.
|
|
|
+ When it is exhausted, new free inodes are found using a linear search.
|
|
|
+
|
|
|
+* Free block management:
|
|
|
+ - Minix FS a bitmap
|
|
|
+ - Xenix FS, SystemV FS, Coherent FS
|
|
|
+ Free blocks are organized in a "free list". Maybe a misleading term,
|
|
|
+ since it is not true that every free block contains a pointer to
|
|
|
+ the next free block. Rather, the free blocks are organized in chunks
|
|
|
+ of limited size, and every now and then a free block contains pointers
|
|
|
+ to the free blocks pertaining to the next chunk; the first of these
|
|
|
+ contains pointers and so on. The list terminates with a "block number"
|
|
|
+ 0 on Xenix FS and SystemV FS, with a block zeroed out on Coherent FS.
|
|
|
+
|
|
|
+* Super-block location:
|
|
|
+ - Minix FS block 1 = bytes 1024..2047
|
|
|
+ - Xenix FS block 1 = bytes 1024..2047
|
|
|
+ - SystemV FS bytes 512..1023
|
|
|
+ - Coherent FS block 1 = bytes 512..1023
|
|
|
+
|
|
|
+* Super-block layout:
|
|
|
+ - Minix FS
|
|
|
+ unsigned short s_ninodes;
|
|
|
+ unsigned short s_nzones;
|
|
|
+ unsigned short s_imap_blocks;
|
|
|
+ unsigned short s_zmap_blocks;
|
|
|
+ unsigned short s_firstdatazone;
|
|
|
+ unsigned short s_log_zone_size;
|
|
|
+ unsigned long s_max_size;
|
|
|
+ unsigned short s_magic;
|
|
|
+ - Xenix FS, SystemV FS, Coherent FS
|
|
|
+ unsigned short s_firstdatazone;
|
|
|
+ unsigned long s_nzones;
|
|
|
+ unsigned short s_fzone_count;
|
|
|
+ unsigned long s_fzones[NICFREE];
|
|
|
+ unsigned short s_finode_count;
|
|
|
+ unsigned short s_finodes[NICINOD];
|
|
|
+ char s_flock;
|
|
|
+ char s_ilock;
|
|
|
+ char s_modified;
|
|
|
+ char s_rdonly;
|
|
|
+ unsigned long s_time;
|
|
|
+ short s_dinfo[4]; -- SystemV FS only
|
|
|
+ unsigned long s_free_zones;
|
|
|
+ unsigned short s_free_inodes;
|
|
|
+ short s_dinfo[4]; -- Xenix FS only
|
|
|
+ unsigned short s_interleave_m,s_interleave_n; -- Coherent FS only
|
|
|
+ char s_fname[6];
|
|
|
+ char s_fpack[6];
|
|
|
+ then they differ considerably:
|
|
|
+ Xenix FS
|
|
|
+ char s_clean;
|
|
|
+ char s_fill[371];
|
|
|
+ long s_magic;
|
|
|
+ long s_type;
|
|
|
+ SystemV FS
|
|
|
+ long s_fill[12 or 14];
|
|
|
+ long s_state;
|
|
|
+ long s_magic;
|
|
|
+ long s_type;
|
|
|
+ Coherent FS
|
|
|
+ unsigned long s_unique;
|
|
|
+ Note that Coherent FS has no magic.
|
|
|
+
|
|
|
+* Inode layout:
|
|
|
+ - Minix FS
|
|
|
+ unsigned short i_mode;
|
|
|
+ unsigned short i_uid;
|
|
|
+ unsigned long i_size;
|
|
|
+ unsigned long i_time;
|
|
|
+ unsigned char i_gid;
|
|
|
+ unsigned char i_nlinks;
|
|
|
+ unsigned short i_zone[7+1+1];
|
|
|
+ - Xenix FS, SystemV FS, Coherent FS
|
|
|
+ unsigned short i_mode;
|
|
|
+ unsigned short i_nlink;
|
|
|
+ unsigned short i_uid;
|
|
|
+ unsigned short i_gid;
|
|
|
+ unsigned long i_size;
|
|
|
+ unsigned char i_zone[3*(10+1+1+1)];
|
|
|
+ unsigned long i_atime;
|
|
|
+ unsigned long i_mtime;
|
|
|
+ unsigned long i_ctime;
|
|
|
+
|
|
|
+* Regular file data blocks are organized as
|
|
|
+ - Minix FS
|
|
|
+ 7 direct blocks
|
|
|
+ 1 indirect block (pointers to blocks)
|
|
|
+ 1 double-indirect block (pointer to pointers to blocks)
|
|
|
+ - Xenix FS, SystemV FS, Coherent FS
|
|
|
+ 10 direct blocks
|
|
|
+ 1 indirect block (pointers to blocks)
|
|
|
+ 1 double-indirect block (pointer to pointers to blocks)
|
|
|
+ 1 triple-indirect block (pointer to pointers to pointers to blocks)
|
|
|
+
|
|
|
+* Inode size, inodes per block
|
|
|
+ - Minix FS 32 32
|
|
|
+ - Xenix FS 64 16
|
|
|
+ - SystemV FS 64 16
|
|
|
+ - Coherent FS 64 8
|
|
|
+
|
|
|
+* Directory entry on disk
|
|
|
+ - Minix FS
|
|
|
+ unsigned short inode;
|
|
|
+ char name[14/30];
|
|
|
+ - Xenix FS, SystemV FS, Coherent FS
|
|
|
+ unsigned short inode;
|
|
|
+ char name[14];
|
|
|
+
|
|
|
+* Dir entry size, dir entries per block
|
|
|
+ - Minix FS 16/32 64/32
|
|
|
+ - Xenix FS 16 64
|
|
|
+ - SystemV FS 16 64
|
|
|
+ - Coherent FS 16 32
|
|
|
+
|
|
|
+* How to implement symbolic links such that the host fsck doesn't scream:
|
|
|
+ - Minix FS normal
|
|
|
+ - Xenix FS kludge: as regular files with chmod 1000
|
|
|
+ - SystemV FS ??
|
|
|
+ - Coherent FS kludge: as regular files with chmod 1000
|
|
|
|
|
|
-Bruno Haible
|
|
|
-<haible@ma2s2.mathematik.uni-karlsruhe.de>
|
|
|
|
|
|
+Notation: We often speak of a "block" but mean a zone (the allocation unit)
|
|
|
+and not the disk driver's notion of "block".
|
Adrian Bunk