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source | linux | .. SPDX-License-Identifier: GPL-2.0
===============
Ext3 Filesystem
===============
Ext3 was originally released in September 1999. Written by Stephen Tweedie
for the 2.2 branch, and ported to 2.4 kernels by Peter Braam, Andreas Dilger,
Andrew Morton, Alexander Viro, Ted Ts'o and Stephen Tweedie.
Ext3 is the ext2 fi... | Documentation/filesystems/ext3.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=================================
Flash-Friendly File System (F2FS)
=================================
Overview
========
NAND flash memory-based storage devices, such as SSD, eMMC, and SD cards, have
been equipped on a variety systems ranging from mobile to server systems. Since
th... | Documentation/filesystems/f2fs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
============
Fiemap Ioctl
============
The fiemap ioctl is an efficient method for userspace to get file
extent mappings. Instead of block-by-block mapping (such as bmap), fiemap
returns a list of extents.
Request Basics
--------------
A fiemap request is encoded within struct f... | Documentation/filesystems/fiemap.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
===================================
File management in the Linux kernel
===================================
This document describes how locking for files (struct file)
and file descriptor table (struct files) works.
Up until 2.6.12, the file descriptor table has been protected
wit... | Documentation/filesystems/files.rst | null | null | null | null | null |
source | linux | =====================================
Filesystem-level encryption (fscrypt)
=====================================
Introduction
============
fscrypt is a library which filesystems can hook into to support
transparent encryption of files and directories.
Note: "fscrypt" in this document refers to the kernel-level port... | Documentation/filesystems/fscrypt.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
.. _fsverity:
=======================================================
fs-verity: read-only file-based authenticity protection
=======================================================
Introduction
============
fs-verity (``fs/verity/``) is a support layer that filesystems can
hook ... | Documentation/filesystems/fsverity.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
==================================
Macintosh HFS Filesystem for Linux
==================================
.. Note:: This filesystem doesn't have a maintainer.
HFS stands for ``Hierarchical File System`` and is the filesystem used
by the Mac Plus and all later Macintosh models. E... | Documentation/filesystems/hfs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
======================================
Macintosh HFSPlus Filesystem for Linux
======================================
HFSPlus is a filesystem first introduced in MacOS 8.1.
HFSPlus has several extensions to HFS, including 32-bit allocation
blocks, 255-character unicode filenames, an... | Documentation/filesystems/hfsplus.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
====================
Read/Write HPFS 2.09
====================
1998-2004, Mikulas Patocka
:email: mikulas@artax.karlin.mff.cuni.cz
:homepage: https://artax.karlin.mff.cuni.cz/~mikulas/vyplody/hpfs/index-e.cgi
Credits
=======
Chris Smith, 1993, original read-only HPFS, some code a... | Documentation/filesystems/hpfs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Idmappings
==========
Most filesystem developers will have encountered idmappings. They are used when
reading from or writing ownership to disk, reporting ownership to userspace, or
for permission checking. This document is aimed at filesystem developers that
want to know how idmap... | Documentation/filesystems/idmappings.rst | null | null | null | null | null |
source | linux | .. _filesystems_index:
===============================
Filesystems in the Linux kernel
===============================
This under-development manual will, some glorious day, provide
comprehensive information on how the Linux virtual filesystem (VFS) layer
works, along with the filesystems that sit below it. For now,... | Documentation/filesystems/index.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
===============================================================
Inotify - A Powerful yet Simple File Change Notification System
===============================================================
Document started 15 Mar 2005 by Robert Love <rml@novell.com>
Document updated 4 Jan 201... | Documentation/filesystems/inotify.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
==================
ISO9660 Filesystem
==================
Mount options that are the same as for msdos and vfat partitions.
========= ========================================================
gid=nnn All files in the partition will be in group nnn.
uid=nnn All files in the par... | Documentation/filesystems/isofs.rst | null | null | null | null | null |
source | linux | The Linux Journalling API
=========================
Overview
--------
Details
~~~~~~~
The journalling layer is easy to use. You need to first of all create a
journal_t data structure. There are two calls to do this dependent on
how you decide to allocate the physical media on which the journal
resides. The jbd2_jour... | Documentation/filesystems/journalling.rst | null | null | null | null | null |
source | linux | =======
Locking
=======
The text below describes the locking rules for VFS-related methods.
It is (believed to be) up-to-date. *Please*, if you change anything in
prototypes or locking protocols - update this file. And update the relevant
instances in the tree, don't leave that to maintainers of filesystems/devices/
e... | Documentation/filesystems/locking.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
==========================
File Locking Release Notes
==========================
Andy Walker <andy@lysaker.kvaerner.no>
12 May 1997
1. What's New?
==============
1.1 Broken Flock Emulation
--------------------------
The old flock(2) emulation in the kernel was swapped... | Documentation/filesystems/locks.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
====================
Filesystem Mount API
====================
.. CONTENTS
(1) Overview.
(2) The filesystem context.
(3) The filesystem context operations.
(4) Filesystem context security.
(5) VFS filesystem context API.
(6) Superblock creation helpers.
(7) Parameter ... | Documentation/filesystems/mount_api.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=====================
Multigrain Timestamps
=====================
Introduction
============
Historically, the kernel has always used coarse time values to stamp inodes.
This value is updated every jiffy, so any change that happens within that jiffy
will end up with the same timesta... | Documentation/filesystems/multigrain-ts.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
===================================
Network Filesystem Services Library
===================================
.. Contents:
- Overview.
- Requests and streams.
- Subrequests.
- Result collection and retry.
- Local caching.
- Content encryption (fscrypt).
- Per-inode ... | Documentation/filesystems/netfs_library.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
======
NILFS2
======
NILFS2 is a log-structured file system (LFS) supporting continuous
snapshotting. In addition to versioning capability of the entire file
system, users can even restore files mistakenly overwritten or
destroyed just a few seconds ago. Since NILFS2 can keep con... | Documentation/filesystems/nilfs2.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=====
NTFS3
=====
Summary and Features
====================
NTFS3 is fully functional NTFS Read-Write driver. The driver works with NTFS
versions up to 3.1. File system type to use on mount is *ntfs3*.
- This driver implements NTFS read/write support for normal, sparse and
comp... | Documentation/filesystems/ntfs3.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=====================================
OCFS2 file system - online file check
=====================================
This document will describe OCFS2 online file check feature.
Introduction
============
OCFS2 is often used in high-availability systems. However, OCFS2 usually
convert... | Documentation/filesystems/ocfs2-online-filecheck.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
================
OCFS2 filesystem
================
OCFS2 is a general purpose extent based shared disk cluster file
system with many similarities to ext3. It supports 64 bit inode
numbers, and has automatically extending metadata groups which may
also make it attractive for non-clu... | Documentation/filesystems/ocfs2.rst | null | null | null | null | null |
source | linux | .. 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... | Documentation/filesystems/omfs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
========
ORANGEFS
========
OrangeFS is an LGPL userspace scale-out parallel storage system. It is ideal
for large storage problems faced by HPC, BigData, Streaming Video,
Genomics, Bioinformatics.
Orangefs, originally called PVFS, was first developed in 1993 by
Walt Ligon and Eric... | Documentation/filesystems/orangefs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Written by: Neil Brown
Please see MAINTAINERS file for where to send questions.
Overlay Filesystem
==================
This document describes a prototype for a new approach to providing
overlay-filesystem functionality in Linux (sometimes referred to as
union-filesystems). An ove... | Documentation/filesystems/overlayfs.rst | null | null | null | null | null |
source | linux | ===============
Pathname lookup
===============
This write-up is based on three articles published at lwn.net:
- <https://lwn.net/Articles/649115/> Pathname lookup in Linux
- <https://lwn.net/Articles/649729/> RCU-walk: faster pathname lookup in Linux
- <https://lwn.net/Articles/650786/> A walk among the symlinks
Wr... | Documentation/filesystems/path-lookup.rst | null | null | null | null | null |
source | linux | Path walking and name lookup locking
====================================
Path resolution is the finding a dentry corresponding to a path name string, by
performing a path walk. Typically, for every open(), stat() etc., the path name
will be resolved. Paths are resolved by walking the namespace tree, starting
with the... | Documentation/filesystems/path-lookup.txt | null | null | null | null | null |
source | linux | ====================
Changes since 2.5.0:
====================
---
**recommended**
New helpers: sb_bread(), sb_getblk(), sb_find_get_block(), set_bh(),
sb_set_blocksize() and sb_min_blocksize().
Use them.
(sb_find_get_block() replaces 2.4's get_hash_table())
---
**recommended**
New methods: ->alloc_inode() and ... | Documentation/filesystems/porting.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
====================
The /proc Filesystem
====================
===================== ======================================= ================
/proc/sys Terrehon Bowden <terrehon@pacbell.net>, October 7 1999
Bodo Bauer <bb@ricochet.net>
2.4.x u... | Documentation/filesystems/proc.rst | null | null | null | null | null |
source | linux | Notes on propagate_umount()
Umount propagation starts with a set of mounts we are already going to
take out. Ideally, we would like to add all downstream cognates to
that set - anything with the same mountpoint as one of the removed
mounts and with parent that would receive events from the parent of that
mount. Howe... | Documentation/filesystems/propagate_umount.txt | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
===================
The QNX6 Filesystem
===================
The qnx6fs is used by newer QNX operating system versions. (e.g. Neutrino)
It got introduced in QNX 6.4.0 and is used default since 6.4.1.
Option
======
mmi_fs Mount filesystem as used for example by Audi MMI 3G system
... | Documentation/filesystems/qnx6.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
===============
Quota subsystem
===============
Quota subsystem allows system administrator to set limits on used space and
number of used inodes (inode is a filesystem structure which is associated with
each file or directory) for users and/or groups. For both used space and numbe... | Documentation/filesystems/quota.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
===========================
Ramfs, rootfs and initramfs
===========================
October 17, 2005
:Author: Rob Landley <rob@landley.net>
What is ramfs?
--------------
Ramfs is a very simple filesystem that exports Linux's disk caching
mechanisms (the page cache and dentry cac... | Documentation/filesystems/ramfs-rootfs-initramfs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
==================================
relay interface (formerly relayfs)
==================================
The relay interface provides a means for kernel applications to
efficiently log and transfer large quantities of data from the kernel
to userspace via user-defined 'relay channe... | Documentation/filesystems/relay.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
.. include:: <isonum.txt>
=====================================================
User Interface for Resource Control feature (resctrl)
=====================================================
:Copyright: |copy| 2016 Intel Corporation
:Authors: - Fenghua Yu <fenghua.yu@intel.com>
... | Documentation/filesystems/resctrl.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=======================
ROMFS - ROM File System
=======================
This is a quite dumb, read only filesystem, mainly for initial RAM
disks of installation disks. It has grown up by the need of having
modules linked at boot time. Using this filesystem, you get a very
similar... | Documentation/filesystems/romfs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
======================
The seq_file Interface
======================
Copyright 2003 Jonathan Corbet <corbet@lwn.net>
This file is originally from the LWN.net Driver Porting series at
https://lwn.net/Articles/driver-porting/
There are numerous ways for a device driver (or othe... | Documentation/filesystems/seq_file.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
===============
Shared Subtrees
===============
.. Contents:
1) Overview
2) Features
3) Setting mount states
4) Use-case
5) Detailed semantics
6) Quiz
7) FAQ
8) Implementation
1) Overview
-----------
Consider the following situation:
A process wants to clone its own nam... | Documentation/filesystems/sharedsubtree.rst | null | null | null | null | null |
source | linux | ================
splice and pipes
================
splice API
==========
splice is a method for moving blocks of data around inside the kernel,
without continually transferring them between the kernel and user space.
.. kernel-doc:: fs/splice.c
pipes API
=========
Pipe interfaces are all for in-kernel (builtin ima... | Documentation/filesystems/splice.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=======================
Squashfs 4.0 Filesystem
=======================
Squashfs is a compressed read-only filesystem for Linux.
It uses zlib, lz4, lzo, xz or zstd compression to compress files, inodes and
directories. Inodes in the system are very small and all blocks are packed... | Documentation/filesystems/squashfs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=====================================================
sysfs - _The_ filesystem for exporting kernel objects
=====================================================
Patrick Mochel <mochel@osdl.org>
Mike Murphy <mamurph@cs.clemson.edu>
:Revised: 16 August 2011
:Original: 10 Janu... | Documentation/filesystems/sysfs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=====
Tmpfs
=====
Tmpfs is a file system which keeps all of its files in virtual memory.
Everything in tmpfs is temporary in the sense that no files will be
created on your hard drive. If you unmount a tmpfs instance,
everything stored therein is lost.
tmpfs puts everything into... | Documentation/filesystems/tmpfs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
.. UBIFS Authentication
.. sigma star gmbh
.. 2018
============================
UBIFS Authentication Support
============================
Introduction
============
UBIFS utilizes the fscrypt framework to provide confidentiality for file
contents and file names. This prevents atta... | Documentation/filesystems/ubifs-authentication.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
===============
UBI File System
===============
Introduction
============
UBIFS file-system stands for UBI File System. UBI stands for "Unsorted
Block Images". UBIFS is a flash file system, which means it is designed
to work with flash devices. It is important to understand, that ... | Documentation/filesystems/ubifs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
===============
UDF file system
===============
If you encounter problems with reading UDF discs using this driver,
please report them according to MAINTAINERS file.
Write support requires a block driver which supports writing. Currently
dvd+rw drives and media support true rando... | Documentation/filesystems/udf.rst | null | null | null | null | null |
source | linux | ====
VFAT
====
USING VFAT
==========
To use the vfat filesystem, use the filesystem type 'vfat'. i.e.::
mount -t vfat /dev/fd0 /mnt
No special partition formatter is required,
'mkdosfs' will work fine if you want to format from within Linux.
VFAT MOUNT OPTIONS
==================
**uid=###**
Set the owner of ... | Documentation/filesystems/vfat.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=========================================
Overview of the Linux Virtual File System
=========================================
Original author: Richard Gooch <rgooch@atnf.csiro.au>
- Copyright (C) 1999 Richard Gooch
- Copyright (C) 2005 Pekka Enberg
Introduction
============
The... | Documentation/filesystems/vfs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
.. _virtiofs_index:
===================================================
virtiofs: virtio-fs host<->guest shared file system
===================================================
- Copyright (C) 2019 Red Hat, Inc.
Introduction
============
The virtiofs file system for Linux implemen... | Documentation/filesystems/virtiofs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
================================================
ZoneFS - Zone filesystem for Zoned block devices
================================================
Introduction
============
zonefs is a very simple file system exposing each zone of a zoned block device
as a file. Unlike a regular P... | Documentation/filesystems/zonefs.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=================
Cache Backend API
=================
The FS-Cache system provides an API by which actual caches can be supplied to
FS-Cache for it to then serve out to network filesystems and other interested
parties. This API is used by::
#include <linux/fscache-cache.h>.
Ov... | Documentation/filesystems/caching/backend-api.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
===================================
Cache on Already Mounted Filesystem
===================================
.. Contents:
(*) Overview.
(*) Requirements.
(*) Configuration.
(*) Starting the cache.
(*) Things to avoid.
(*) Cache culling.
(*) Cache structure.
(*) Secur... | Documentation/filesystems/caching/cachefiles.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
==========================
General Filesystem Caching
==========================
Overview
========
This facility is a general purpose cache for network filesystems, though it
could be used for caching other things such as ISO9660 filesystems too.
FS-Cache mediates between cache b... | Documentation/filesystems/caching/fscache.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Filesystem Caching
==================
.. toctree::
:maxdepth: 2
fscache
netfs-api
backend-api
cachefiles | Documentation/filesystems/caching/index.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
==============================
Network Filesystem Caching API
==============================
Fscache provides an API by which a network filesystem can make use of local
caching facilities. The API is arranged around a number of principles:
(1) A cache is logically organised into... | Documentation/filesystems/caching/netfs-api.rst | null | null | null | null | null |
source | linux | .. 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**: ... | Documentation/filesystems/ext4/about.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Block and Inode Allocation Policy
---------------------------------
ext4 recognizes (better than ext3, anyway) that data locality is
generally a desirably quality of a filesystem. On a spinning disk,
keeping related blocks near each other reduces the amount of movement
that the hea... | Documentation/filesystems/ext4/allocators.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
.. _atomic_writes:
Atomic Block Writes
-------------------------
Introduction
~~~~~~~~~~~~
Atomic (untorn) block writes ensure that either the entire write is committed
to disk or none of it is. This prevents "torn writes" during power loss or
system crashes. The ext4 filesystem s... | Documentation/filesystems/ext4/atomic_writes.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Extended Attributes
-------------------
Extended attributes (xattrs) are typically stored in a separate data
block on the disk and referenced from inodes via ``inode.i_file_acl*``.
The first use of extended attributes seems to have been for storing file
ACLs and other security data... | Documentation/filesystems/ext4/attributes.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Bigalloc
--------
At the moment, the default size of a block is 4KiB, which is a commonly
supported page size on most MMU-capable hardware. This is fortunate, as
ext4 code is not prepared to handle the case where the block size
exceeds the page size. However, for a filesystem of mo... | Documentation/filesystems/ext4/bigalloc.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Block and inode Bitmaps
-----------------------
The data block bitmap tracks the usage of data blocks within the block
group.
The inode bitmap records which entries in the inode table are in use.
As with most bitmaps, one bit represents the usage status of one data
block or inode... | Documentation/filesystems/ext4/bitmaps.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Block Groups
------------
Layout
~~~~~~
The layout of a standard block group is approximately as follows (each
of these fields is discussed in a separate section below):
.. list-table::
:widths: 1 1 1 1 1 1 1 1
:header-rows: 1
* - Group 0 Padding
- ext4 Super Block... | Documentation/filesystems/ext4/blockgroup.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| i.i_block Offset | Where It Poi... | Documentation/filesystems/ext4/blockmap.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Blocks
------
ext4 allocates storage space in units of “blocks”. A block is a group of
sectors between 1KiB and 64KiB, and the number of sectors must be an
integral power of 2. Blocks are in turn grouped into larger units called
block groups. Block size is specified at mkfs time an... | Documentation/filesystems/ext4/blocks.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Checksums
---------
Starting in early 2012, metadata checksums were added to all major ext4
and jbd2 data structures. The associated feature flag is metadata_csum.
The desired checksum algorithm is indicated in the superblock, though as
of October 2012 the only supported algorithm ... | Documentation/filesystems/ext4/checksums.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Directory Entries
-----------------
In an ext4 filesystem, a directory is more or less a flat file that maps
an arbitrary byte string (usually ASCII) to an inode number on the
filesystem. There can be many directory entries across the filesystem
that reference the same inode number... | Documentation/filesystems/ext4/directory.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Dynamic Structures
==================
Dynamic metadata are created on the fly when files and blocks are
allocated to files.
.. toctree::
inodes
ifork
directory
attributes | Documentation/filesystems/ext4/dynamic.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Large Extended Attribute Values
-------------------------------
To enable ext4 to store extended attribute values that do not fit in the
inode or in the single extended attribute block attached to an inode,
the EA_INODE feature allows us to store the value in the data blocks of
a r... | Documentation/filesystems/ext4/eainode.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Global Structures
=================
The filesystem is sharded into a number of block groups, each of which
have static metadata at fixed locations.
.. toctree::
super
group_descr
bitmaps
inode_table
mmp
journal
orphan | Documentation/filesystems/ext4/globals.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Block Group Descriptors
-----------------------
Each block group on the filesystem has one of these descriptors
associated with it. As noted in the Layout section above, the group
descriptors (if present) are the second item in the block group. The
standard configuration is for eac... | Documentation/filesystems/ext4/group_descr.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
The Contents of inode.i_block
------------------------------
Depending on the type of file an inode describes, the 60 bytes of
storage in ``inode.i_block`` can be used in different ways. In general,
regular files and directories will use it for file block indexing
information, and ... | Documentation/filesystems/ext4/ifork.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
===================================
ext4 Data Structures and Algorithms
===================================
.. toctree::
:maxdepth: 2
:numbered:
about
overview
globals
dynamic | Documentation/filesystems/ext4/index.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Inline Data
-----------
The inline data feature was designed to handle the case that a file's
data is so tiny that it readily fits inside the inode, which
(theoretically) reduces disk block consumption and reduces seeks. If the
file is smaller than 60 bytes, then the data are store... | Documentation/filesystems/ext4/inlinedata.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Inode Table
-----------
Inode tables are statically allocated at mkfs time. Each block group
descriptor points to the start of the table, and the superblock records
the number of inodes per group. See :doc:`inode documentation <inodes>`
for more information on inode table layout. | Documentation/filesystems/ext4/inode_table.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Index Nodes
-----------
In a regular UNIX filesystem, the inode stores all the metadata
pertaining to the file (time stamps, block maps, extended attributes,
etc), not the directory entry. To find the information associated with a
file, one must traverse the directory files to find... | Documentation/filesystems/ext4/inodes.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Journal (jbd2)
--------------
Introduced in ext3, the ext4 filesystem employs a journal to protect the
filesystem against metadata inconsistencies in the case of a system crash. Up
to 10,240,000 file system blocks (see man mke2fs(8) for more details on journal
size limits) can be r... | Documentation/filesystems/ext4/journal.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Multiple Mount Protection
-------------------------
Multiple mount protection (MMP) is a feature that protects the
filesystem against multiple hosts trying to use the filesystem
simultaneously. When a filesystem is opened (for mounting, or fsck,
etc.), the MMP code running on the n... | Documentation/filesystems/ext4/mmp.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Orphan file
-----------
In unix there can inodes that are unlinked from directory hierarchy but that
are still alive because they are open. In case of crash the filesystem has to
clean up these inodes as otherwise they (and the blocks referenced from them)
would leak. Similarly if ... | Documentation/filesystems/ext4/orphan.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
High Level Design
=================
An ext4 file system is split into a series of block groups. To reduce
performance difficulties due to fragmentation, the block allocator tries
very hard to keep each file's blocks within the same group, thereby
reducing seek times. The size of a ... | Documentation/filesystems/ext4/overview.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Special inodes
--------------
ext4 reserves some inode for special features, as follows:
.. list-table::
:widths: 6 70
:header-rows: 1
* - inode Number
- Purpose
* - 0
- Doesn't exist; there is no inode 0.
* - 1
- List of defective blocks.
* - 2
... | Documentation/filesystems/ext4/special_inodes.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Super Block
-----------
The superblock records various information about the enclosing
filesystem, such as block counts, inode counts, supported features,
maintenance information, and more.
If the sparse_super feature flag is set, redundant copies of the
superblock and group descr... | Documentation/filesystems/ext4/super.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
Verity files
------------
ext4 supports fs-verity, which is a filesystem feature that provides
Merkle tree based hashing for individual readonly files. Most of
fs-verity is common to all filesystems that support it; see
:ref:`Documentation/filesystems/fsverity.rst <fsverity>` for ... | Documentation/filesystems/ext4/verity.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=======================================
FUSE-over-io-uring design documentation
=======================================
This documentation covers basic details how the fuse
kernel/userspace communication through io-uring is configured
and works. For generic details about FUSE see f... | Documentation/filesystems/fuse/fuse-io-uring.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
==============
FUSE I/O Modes
==============
Fuse supports the following I/O modes:
- direct-io
- cached
+ write-through
+ writeback-cache
The direct-io mode can be selected with the FOPEN_DIRECT_IO flag in the
FUSE_OPEN reply.
In direct-io mode the page cache is completely ... | Documentation/filesystems/fuse/fuse-io.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
================
FUSE Passthrough
================
Introduction
============
FUSE (Filesystem in Userspace) passthrough is a feature designed to improve the
performance of FUSE filesystems for I/O operations. Typically, FUSE operations
involve communication between the kernel and ... | Documentation/filesystems/fuse/fuse-passthrough.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=============
FUSE Overview
=============
Definitions
===========
Userspace filesystem:
A filesystem in which data and metadata are provided by an ordinary
userspace process. The filesystem can be accessed normally through
the kernel interface.
Filesystem daemon:
The pro... | Documentation/filesystems/fuse/fuse.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
======================================================
FUSE (Filesystem in Userspace) Technical Documentation
======================================================
.. toctree::
:maxdepth: 2
:numbered:
fuse
fuse-io
fuse-io-uring
fuse-passthrough | Documentation/filesystems/fuse/index.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
============================
Glock internal locking rules
============================
This documents the basic principles of the glock state machine
internals. Each glock (struct gfs2_glock in fs/gfs2/incore.h)
has two main (internal) locks:
1. A spinlock (gl_lockref.lock) which... | Documentation/filesystems/gfs2/glocks.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
====================
Global File System 2
====================
Overview
========
GFS2 is a cluster file system. It allows a cluster of computers to
simultaneously use a block device that is shared between them (with FC,
iSCSI, NBD, etc). GFS2 reads and writes to the block device ... | Documentation/filesystems/gfs2/index.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
================
uevents and GFS2
================
During the lifetime of a GFS2 mount, a number of uevents are generated.
This document explains what the events are and what they are used
for (by gfs_controld in gfs2-utils).
A list of GFS2 uevents
======================
1. ADD
-... | Documentation/filesystems/gfs2/uevents.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
.. _iomap_design:
..
Dumb style notes to maintain the author's sanity:
Please try to start sentences on separate lines so that
sentence changes don't bleed colors in diff.
Heading decorations are documented in sphinx.rst.
==============
Library Desig... | Documentation/filesystems/iomap/design.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=======================
VFS iomap Documentation
=======================
.. toctree::
:maxdepth: 2
:numbered:
design
operations
porting | Documentation/filesystems/iomap/index.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
.. _iomap_operations:
..
Dumb style notes to maintain the author's sanity:
Please try to start sentences on separate lines so that
sentence changes don't bleed colors in diff.
Heading decorations are documented in sphinx.rst.
========================... | Documentation/filesystems/iomap/operations.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
.. _iomap_porting:
..
Dumb style notes to maintain the author's sanity:
Please try to start sentences on separate lines so that
sentence changes don't bleed colors in diff.
Heading decorations are documented in sphinx.rst.
=======================
Por... | Documentation/filesystems/iomap/porting.rst | null | null | null | null | null |
source | linux | .. SPDX-License-Identifier: GPL-2.0
=======================
NFSv4 client identifier
=======================
This document explains how the NFSv4 protocol identifies client
instances in order to maintain file open and lock state during
system restarts. A special identifier and principal are maintained
on each client. ... | Documentation/filesystems/nfs/client-identifier.rst | null | null | null | null | null |
source | linux | :orphan:
Making Filesystems Exportable
=============================
Overview
--------
All filesystem operations require a dentry (or two) as a starting
point. Local applications have a reference-counted hold on suitable
dentries via open file descriptors or cwd/root. However remote
applications that access a file... | Documentation/filesystems/nfs/exporting.rst | null | null | null | null | null |
source | linux | ===============================
NFS
===============================
.. toctree::
:maxdepth: 1
client-identifier
exporting
localio
pnfs
rpc-cache
rpc-server-gss
nfs41-server
nfsd-io-modes
knfsd-stats
reexport | Documentation/filesystems/nfs/index.rst | null | null | null | null | null |
source | linux | ============================
Kernel NFS Server Statistics
============================
:Authors: Greg Banks <gnb@sgi.com> - 26 Mar 2009
This document describes the format and semantics of the statistics
which the kernel NFS server makes available to userspace. These
statistics are available in several text form pseu... | Documentation/filesystems/nfs/knfsd-stats.rst | null | null | null | null | null |
source | linux | ===========
NFS LOCALIO
===========
Overview
========
The LOCALIO auxiliary RPC protocol allows the Linux NFS client and
server to reliably handshake to determine if they are on the same
host. Select "NFS client and server support for LOCALIO auxiliary
protocol" in menuconfig to enable CONFIG_NFS_LOCALIO in the kerne... | Documentation/filesystems/nfs/localio.rst | null | null | null | null | null |
source | linux | =============================
NFSv4.1 Server Implementation
=============================
Server support for minorversion 1 can be controlled using the
/proc/fs/nfsd/versions control file. The string output returned
by reading this file will contain either "+4.1" or "-4.1"
correspondingly.
Currently, server support ... | Documentation/filesystems/nfs/nfs41-server.rst | null | null | null | null | null |
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