docs: filesystems: convert omfs.txt to ReST
- Add a SPDX header; - Adjust document title; - Mark literal blocks as such; - Add table markups; - Add it to filesystems/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Acked-by: Bob Copeland <me@bobcopeland.com> Link: https://lore.kernel.org/r/0c125c7c971d81a557ca954992b8d770a9d1e3e8.1581955849.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Mauro Carvalho Chehab
Jonathan Corbet
parent
fa95e087ff
commit
7cbb468f0c
@ -78,6 +78,7 @@ Documentation for filesystem implementations.
|
|||||||
ntfs
|
ntfs
|
||||||
ocfs2
|
ocfs2
|
||||||
ocfs2-online-filecheck
|
ocfs2-online-filecheck
|
||||||
|
omfs
|
||||||
overlayfs
|
overlayfs
|
||||||
virtiofs
|
virtiofs
|
||||||
vfat
|
vfat
|
||||||
|
|||||||
112
Documentation/filesystems/omfs.rst
Normal file
112
Documentation/filesystems/omfs.rst
Normal file
@ -0,0 +1,112 @@
|
|||||||
|
.. SPDX-License-Identifier: GPL-2.0
|
||||||
|
|
||||||
|
================================
|
||||||
|
Optimized MPEG Filesystem (OMFS)
|
||||||
|
================================
|
||||||
|
|
||||||
|
Overview
|
||||||
|
========
|
||||||
|
|
||||||
|
OMFS is a filesystem created by SonicBlue for use in the ReplayTV DVR
|
||||||
|
and Rio Karma MP3 player. The filesystem is extent-based, utilizing
|
||||||
|
block sizes from 2k to 8k, with hash-based directories. This
|
||||||
|
filesystem driver may be used to read and write disks from these
|
||||||
|
devices.
|
||||||
|
|
||||||
|
Note, it is not recommended that this FS be used in place of a general
|
||||||
|
filesystem for your own streaming media device. Native Linux filesystems
|
||||||
|
will likely perform better.
|
||||||
|
|
||||||
|
More information is available at:
|
||||||
|
|
||||||
|
http://linux-karma.sf.net/
|
||||||
|
|
||||||
|
Various utilities, including mkomfs and omfsck, are included with
|
||||||
|
omfsprogs, available at:
|
||||||
|
|
||||||
|
http://bobcopeland.com/karma/
|
||||||
|
|
||||||
|
Instructions are included in its README.
|
||||||
|
|
||||||
|
Options
|
||||||
|
=======
|
||||||
|
|
||||||
|
OMFS supports the following mount-time options:
|
||||||
|
|
||||||
|
============ ========================================
|
||||||
|
uid=n make all files owned by specified user
|
||||||
|
gid=n make all files owned by specified group
|
||||||
|
umask=xxx set permission umask to xxx
|
||||||
|
fmask=xxx set umask to xxx for files
|
||||||
|
dmask=xxx set umask to xxx for directories
|
||||||
|
============ ========================================
|
||||||
|
|
||||||
|
Disk format
|
||||||
|
===========
|
||||||
|
|
||||||
|
OMFS discriminates between "sysblocks" and normal data blocks. The sysblock
|
||||||
|
group consists of super block information, file metadata, directory structures,
|
||||||
|
and extents. Each sysblock has a header containing CRCs of the entire
|
||||||
|
sysblock, and may be mirrored in successive blocks on the disk. A sysblock may
|
||||||
|
have a smaller size than a data block, but since they are both addressed by the
|
||||||
|
same 64-bit block number, any remaining space in the smaller sysblock is
|
||||||
|
unused.
|
||||||
|
|
||||||
|
Sysblock header information::
|
||||||
|
|
||||||
|
struct omfs_header {
|
||||||
|
__be64 h_self; /* FS block where this is located */
|
||||||
|
__be32 h_body_size; /* size of useful data after header */
|
||||||
|
__be16 h_crc; /* crc-ccitt of body_size bytes */
|
||||||
|
char h_fill1[2];
|
||||||
|
u8 h_version; /* version, always 1 */
|
||||||
|
char h_type; /* OMFS_INODE_X */
|
||||||
|
u8 h_magic; /* OMFS_IMAGIC */
|
||||||
|
u8 h_check_xor; /* XOR of header bytes before this */
|
||||||
|
__be32 h_fill2;
|
||||||
|
};
|
||||||
|
|
||||||
|
Files and directories are both represented by omfs_inode::
|
||||||
|
|
||||||
|
struct omfs_inode {
|
||||||
|
struct omfs_header i_head; /* header */
|
||||||
|
__be64 i_parent; /* parent containing this inode */
|
||||||
|
__be64 i_sibling; /* next inode in hash bucket */
|
||||||
|
__be64 i_ctime; /* ctime, in milliseconds */
|
||||||
|
char i_fill1[35];
|
||||||
|
char i_type; /* OMFS_[DIR,FILE] */
|
||||||
|
__be32 i_fill2;
|
||||||
|
char i_fill3[64];
|
||||||
|
char i_name[OMFS_NAMELEN]; /* filename */
|
||||||
|
__be64 i_size; /* size of file, in bytes */
|
||||||
|
};
|
||||||
|
|
||||||
|
Directories in OMFS are implemented as a large hash table. Filenames are
|
||||||
|
hashed then prepended into the bucket list beginning at OMFS_DIR_START.
|
||||||
|
Lookup requires hashing the filename, then seeking across i_sibling pointers
|
||||||
|
until a match is found on i_name. Empty buckets are represented by block
|
||||||
|
pointers with all-1s (~0).
|
||||||
|
|
||||||
|
A file is an omfs_inode structure followed by an extent table beginning at
|
||||||
|
OMFS_EXTENT_START::
|
||||||
|
|
||||||
|
struct omfs_extent_entry {
|
||||||
|
__be64 e_cluster; /* start location of a set of blocks */
|
||||||
|
__be64 e_blocks; /* number of blocks after e_cluster */
|
||||||
|
};
|
||||||
|
|
||||||
|
struct omfs_extent {
|
||||||
|
__be64 e_next; /* next extent table location */
|
||||||
|
__be32 e_extent_count; /* total # extents in this table */
|
||||||
|
__be32 e_fill;
|
||||||
|
struct omfs_extent_entry e_entry; /* start of extent entries */
|
||||||
|
};
|
||||||
|
|
||||||
|
Each extent holds the block offset followed by number of blocks allocated to
|
||||||
|
the extent. The final extent in each table is a terminator with e_cluster
|
||||||
|
being ~0 and e_blocks being ones'-complement of the total number of blocks
|
||||||
|
in the table.
|
||||||
|
|
||||||
|
If this table overflows, a continuation inode is written and pointed to by
|
||||||
|
e_next. These have a header but lack the rest of the inode structure.
|
||||||
|
|
||||||
@ -1,106 +0,0 @@
|
|||||||
Optimized MPEG Filesystem (OMFS)
|
|
||||||
|
|
||||||
Overview
|
|
||||||
========
|
|
||||||
|
|
||||||
OMFS is a filesystem created by SonicBlue for use in the ReplayTV DVR
|
|
||||||
and Rio Karma MP3 player. The filesystem is extent-based, utilizing
|
|
||||||
block sizes from 2k to 8k, with hash-based directories. This
|
|
||||||
filesystem driver may be used to read and write disks from these
|
|
||||||
devices.
|
|
||||||
|
|
||||||
Note, it is not recommended that this FS be used in place of a general
|
|
||||||
filesystem for your own streaming media device. Native Linux filesystems
|
|
||||||
will likely perform better.
|
|
||||||
|
|
||||||
More information is available at:
|
|
||||||
|
|
||||||
http://linux-karma.sf.net/
|
|
||||||
|
|
||||||
Various utilities, including mkomfs and omfsck, are included with
|
|
||||||
omfsprogs, available at:
|
|
||||||
|
|
||||||
http://bobcopeland.com/karma/
|
|
||||||
|
|
||||||
Instructions are included in its README.
|
|
||||||
|
|
||||||
Options
|
|
||||||
=======
|
|
||||||
|
|
||||||
OMFS supports the following mount-time options:
|
|
||||||
|
|
||||||
uid=n - make all files owned by specified user
|
|
||||||
gid=n - make all files owned by specified group
|
|
||||||
umask=xxx - set permission umask to xxx
|
|
||||||
fmask=xxx - set umask to xxx for files
|
|
||||||
dmask=xxx - set umask to xxx for directories
|
|
||||||
|
|
||||||
Disk format
|
|
||||||
===========
|
|
||||||
|
|
||||||
OMFS discriminates between "sysblocks" and normal data blocks. The sysblock
|
|
||||||
group consists of super block information, file metadata, directory structures,
|
|
||||||
and extents. Each sysblock has a header containing CRCs of the entire
|
|
||||||
sysblock, and may be mirrored in successive blocks on the disk. A sysblock may
|
|
||||||
have a smaller size than a data block, but since they are both addressed by the
|
|
||||||
same 64-bit block number, any remaining space in the smaller sysblock is
|
|
||||||
unused.
|
|
||||||
|
|
||||||
Sysblock header information:
|
|
||||||
|
|
||||||
struct omfs_header {
|
|
||||||
__be64 h_self; /* FS block where this is located */
|
|
||||||
__be32 h_body_size; /* size of useful data after header */
|
|
||||||
__be16 h_crc; /* crc-ccitt of body_size bytes */
|
|
||||||
char h_fill1[2];
|
|
||||||
u8 h_version; /* version, always 1 */
|
|
||||||
char h_type; /* OMFS_INODE_X */
|
|
||||||
u8 h_magic; /* OMFS_IMAGIC */
|
|
||||||
u8 h_check_xor; /* XOR of header bytes before this */
|
|
||||||
__be32 h_fill2;
|
|
||||||
};
|
|
||||||
|
|
||||||
Files and directories are both represented by omfs_inode:
|
|
||||||
|
|
||||||
struct omfs_inode {
|
|
||||||
struct omfs_header i_head; /* header */
|
|
||||||
__be64 i_parent; /* parent containing this inode */
|
|
||||||
__be64 i_sibling; /* next inode in hash bucket */
|
|
||||||
__be64 i_ctime; /* ctime, in milliseconds */
|
|
||||||
char i_fill1[35];
|
|
||||||
char i_type; /* OMFS_[DIR,FILE] */
|
|
||||||
__be32 i_fill2;
|
|
||||||
char i_fill3[64];
|
|
||||||
char i_name[OMFS_NAMELEN]; /* filename */
|
|
||||||
__be64 i_size; /* size of file, in bytes */
|
|
||||||
};
|
|
||||||
|
|
||||||
Directories in OMFS are implemented as a large hash table. Filenames are
|
|
||||||
hashed then prepended into the bucket list beginning at OMFS_DIR_START.
|
|
||||||
Lookup requires hashing the filename, then seeking across i_sibling pointers
|
|
||||||
until a match is found on i_name. Empty buckets are represented by block
|
|
||||||
pointers with all-1s (~0).
|
|
||||||
|
|
||||||
A file is an omfs_inode structure followed by an extent table beginning at
|
|
||||||
OMFS_EXTENT_START:
|
|
||||||
|
|
||||||
struct omfs_extent_entry {
|
|
||||||
__be64 e_cluster; /* start location of a set of blocks */
|
|
||||||
__be64 e_blocks; /* number of blocks after e_cluster */
|
|
||||||
};
|
|
||||||
|
|
||||||
struct omfs_extent {
|
|
||||||
__be64 e_next; /* next extent table location */
|
|
||||||
__be32 e_extent_count; /* total # extents in this table */
|
|
||||||
__be32 e_fill;
|
|
||||||
struct omfs_extent_entry e_entry; /* start of extent entries */
|
|
||||||
};
|
|
||||||
|
|
||||||
Each extent holds the block offset followed by number of blocks allocated to
|
|
||||||
the extent. The final extent in each table is a terminator with e_cluster
|
|
||||||
being ~0 and e_blocks being ones'-complement of the total number of blocks
|
|
||||||
in the table.
|
|
||||||
|
|
||||||
If this table overflows, a continuation inode is written and pointed to by
|
|
||||||
e_next. These have a header but lack the rest of the inode structure.
|
|
||||||
|
|
||||||
Loading…
Reference in New Issue
Block a user