ext4: import on-disk layout book from wiki page
Create the basic structure of the "new" data structures & algorithms book to be ported over from the on-disk format wiki, and then start by pulling in the introductory information. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
parent
489fcb9124
commit
b2e60723c1
|
@ -14,3 +14,4 @@ the ext4 community.
|
|||
:numbered:
|
||||
|
||||
ext4
|
||||
ondisk/index
|
||||
|
|
|
@ -0,0 +1,44 @@
|
|||
.. SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
About this Book
|
||||
===============
|
||||
|
||||
This document attempts to describe the on-disk format for ext4
|
||||
filesystems. The same general ideas should apply to ext2/3 filesystems
|
||||
as well, though they do not support all the features that ext4 supports,
|
||||
and the fields will be shorter.
|
||||
|
||||
**NOTE**: This is a work in progress, based on notes that the author
|
||||
(djwong) made while picking apart a filesystem by hand. The data
|
||||
structure definitions should be current as of Linux 4.18 and
|
||||
e2fsprogs-1.44. All comments and corrections are welcome, since there is
|
||||
undoubtedly plenty of lore that might not be reflected in freshly
|
||||
created demonstration filesystems.
|
||||
|
||||
License
|
||||
-------
|
||||
This book is licensed under the terms of the GNU Public License, v2.
|
||||
|
||||
Terminology
|
||||
-----------
|
||||
|
||||
ext4 divides a storage device into an array of logical blocks both to
|
||||
reduce bookkeeping overhead and to increase throughput by forcing larger
|
||||
transfer sizes. Generally, the block size will be 4KiB (the same size as
|
||||
pages on x86 and the block layer's default block size), though the
|
||||
actual size is calculated as 2 ^ (10 + ``sb.s_log_block_size``) bytes.
|
||||
Throughout this document, disk locations are given in terms of these
|
||||
logical blocks, not raw LBAs, and not 1024-byte blocks. For the sake of
|
||||
convenience, the logical block size will be referred to as
|
||||
``$block_size`` throughout the rest of the document.
|
||||
|
||||
When referenced in ``preformatted text`` blocks, ``sb`` refers to fields
|
||||
in the super block, and ``inode`` refers to fields in an inode table
|
||||
entry.
|
||||
|
||||
Other References
|
||||
----------------
|
||||
|
||||
Also see http://www.nongnu.org/ext2-doc/ for quite a collection of
|
||||
information about ext2/3. Here's another old reference:
|
||||
http://wiki.osdev.org/Ext2
|
|
@ -0,0 +1,6 @@
|
|||
.. SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
==============================
|
||||
Data Structures and Algorithms
|
||||
==============================
|
||||
.. include:: about.rst
|
Loading…
Reference in New Issue