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docs: filesystems: convert squashfs.txt to ReST

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- Add a SPDX header;
- Adjust document and section titles;
- Mark literal blocks as such;
- Add table markups;
- Add it to filesystems/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/cec30862c7ee7de7f9cd903e35e6c8bf74cc928a.1581955849.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Mauro Carvalho Chehab 2020-02-17 17:12:23 +01:00 committed by Jonathan Corbet
parent 6db0a480aa
commit 31771f45c8
2 changed files with 34 additions and 27 deletions
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1
Documentation/filesystems/index.rst
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@ -86,5 +86,6 @@ Documentation for filesystem implementations.
ramfs-rootfs-initramfs
relay
romfs
squashfs
virtiofs
vfat

60
Documentation/filesystems/squashfs.txt → Documentation/filesystems/squashfs.rst
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@ -1,7 +1,11 @@
SQUASHFS 4.0 FILESYSTEM
.. SPDX-License-Identifier: GPL-2.0
=======================
Squashfs 4.0 Filesystem
=======================
Squashfs is a compressed read-only filesystem for Linux.
It uses zlib, lz4, lzo, or xz compression to compress files, inodes and
directories. Inodes in the system are very small and all blocks are packed to
minimise data overhead. Block sizes greater than 4K are supported up to a
@ -15,31 +19,33 @@ needed.
Mailing list: squashfs-devel@lists.sourceforge.net
Web site: www.squashfs.org
1. FILESYSTEM FEATURES
1. Filesystem Features
----------------------
Squashfs filesystem features versus Cramfs:
============================== ========= ==========
Squashfs Cramfs
Max filesystem size: 2^64 256 MiB
Max file size: ~ 2 TiB 16 MiB
Max files: unlimited unlimited
Max directories: unlimited unlimited
Max entries per directory: unlimited unlimited
Max block size: 1 MiB 4 KiB
Metadata compression: yes no
Directory indexes: yes no
Sparse file support: yes no
Tail-end packing (fragments): yes no
Exportable (NFS etc.): yes no
Hard link support: yes no
"." and ".." in readdir: yes no
Real inode numbers: yes no
32-bit uids/gids: yes no
File creation time: yes no
Xattr support: yes no
ACL support: no no
============================== ========= ==========
Max filesystem size 2^64 256 MiB
Max file size ~ 2 TiB 16 MiB
Max files unlimited unlimited
Max directories unlimited unlimited
Max entries per directory unlimited unlimited
Max block size 1 MiB 4 KiB
Metadata compression yes no
Directory indexes yes no
Sparse file support yes no
Tail-end packing (fragments) yes no
Exportable (NFS etc.) yes no
Hard link support yes no
"." and ".." in readdir yes no
Real inode numbers yes no
32-bit uids/gids yes no
File creation time yes no
Xattr support yes no
ACL support no no
============================== ========= ==========
Squashfs compresses data, inodes and directories. In addition, inode and
directory data are highly compacted, and packed on byte boundaries. Each
@ -47,7 +53,7 @@ compressed inode is on average 8 bytes in length (the exact length varies on
file type, i.e. regular file, directory, symbolic link, and block/char device
inodes have different sizes).
2. USING SQUASHFS
2. Using Squashfs
-----------------
As squashfs is a read-only filesystem, the mksquashfs program must be used to
@ -58,11 +64,11 @@ obtained from this site also.
The squashfs-tools development tree is now located on kernel.org
git://git.kernel.org/pub/scm/fs/squashfs/squashfs-tools.git
3. SQUASHFS FILESYSTEM DESIGN
3. Squashfs Filesystem Design
-----------------------------
A squashfs filesystem consists of a maximum of nine parts, packed together on a
byte alignment:
byte alignment::
---------------
| superblock |
@ -229,15 +235,15 @@ location of the xattr list inside each inode, a 32-bit xattr id
is stored. This xattr id is mapped into the location of the xattr
list using a second xattr id lookup table.
4. TODOS AND OUTSTANDING ISSUES
4. TODOs and Outstanding Issues
-------------------------------
4.1 Todo list
4.1 TODO list
-------------
Implement ACL support.
4.2 Squashfs internal cache
4.2 Squashfs Internal Cache
---------------------------
Blocks in Squashfs are compressed. To avoid repeatedly decompressing