@@ -88,5 +88,6 @@ Documentation for filesystem implementations.
romfs
squashfs
sysfs
+ sysv-fs
virtiofs
vfat
similarity index 73%
rename from Documentation/filesystems/sysv-fs.txt
rename to Documentation/filesystems/sysv-fs.rst
@@ -1,25 +1,40 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================
+SystemV Filesystem
+==================
+
It implements all of
- Xenix FS,
- SystemV/386 FS,
- Coherent FS.
To install:
+
* Answer the 'System V and Coherent filesystem support' question with 'y'
when configuring the kernel.
-* To mount a disk or a partition, use
+* To mount a disk or a partition, use::
+
mount [-r] -t sysv device mountpoint
- The file system type names
+
+ The file system type names::
+
-t sysv
-t xenix
-t coherent
+
may be used interchangeably, but the last two will eventually disappear.
Bugs in the present implementation:
+
- Coherent FS:
+
- The "free list interleave" n:m is currently ignored.
- Only file systems with no filesystem name and no pack name are recognized.
- (See Coherent "man mkfs" for a description of these features.)
+ (See Coherent "man mkfs" for a description of these features.)
+
- SystemV Release 2 FS:
+
The superblock is only searched in the blocks 9, 15, 18, which
corresponds to the beginning of track 1 on floppy disks. No support
for this FS on hard disk yet.
@@ -28,12 +43,14 @@ Bugs in the present implementation:
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)
@@ -45,37 +62,51 @@ These filesystems are rather similar. Here is a comparison with Minix FS:
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
+
+ ================================= ==
+ 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
+
+ =========== =========
+ Minix FS 250
+ Xenix FS ??
+ SystemV FS ??
+ Coherent FS >=10000
+ =========== =========
* Free inode management:
- - Minix FS a bitmap
+
+ - 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
+
+ - 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
@@ -86,13 +117,18 @@ These filesystems are rather similar. Here is a comparison with Minix FS:
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
+
+ =========== ==========================
+ 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
+
+ - Minix FS::
+
unsigned short s_ninodes;
unsigned short s_nzones;
unsigned short s_imap_blocks;
@@ -101,7 +137,9 @@ These filesystems are rather similar. Here is a comparison with Minix FS:
unsigned short s_log_zone_size;
unsigned long s_max_size;
unsigned short s_magic;
- - Xenix FS, SystemV FS, Coherent FS
+
+ - Xenix FS, SystemV FS, Coherent FS::
+
unsigned short s_firstdatazone;
unsigned long s_nzones;
unsigned short s_fzone_count;
@@ -120,23 +158,33 @@ These filesystems are rather similar. Here is a comparison with Minix FS:
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
+
+ Xenix FS::
+
char s_clean;
char s_fill[371];
long s_magic;
long s_type;
- SystemV FS
+
+ SystemV FS::
+
long s_fill[12 or 14];
long s_state;
long s_magic;
long s_type;
- Coherent FS
+
+ Coherent FS::
+
unsigned long s_unique;
+
Note that Coherent FS has no magic.
* Inode layout:
- - Minix FS
+
+ - Minix FS::
+
unsigned short i_mode;
unsigned short i_uid;
unsigned long i_size;
@@ -144,7 +192,9 @@ These filesystems are rather similar. Here is a comparison with Minix FS:
unsigned char i_gid;
unsigned char i_nlinks;
unsigned short i_zone[7+1+1];
- - Xenix FS, SystemV FS, Coherent FS
+
+ - Xenix FS, SystemV FS, Coherent FS::
+
unsigned short i_mode;
unsigned short i_nlink;
unsigned short i_uid;
@@ -155,38 +205,55 @@ These filesystems are rather similar. Here is a comparison with Minix FS:
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
+
+ - 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
+
+ - Minix FS::
+
unsigned short inode;
char name[14/30];
- - Xenix FS, SystemV FS, Coherent FS
+
+ - 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
+ =========== ============== =====================
+ 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 ??
- Add a SPDX header; - Add a document title; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add table markups; - Add it to filesystems/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> --- Documentation/filesystems/index.rst | 1 + .../filesystems/{sysv-fs.txt => sysv-fs.rst} | 155 +++++++++++++----- 2 files changed, 112 insertions(+), 44 deletions(-) rename Documentation/filesystems/{sysv-fs.txt => sysv-fs.rst} (73%)