Commit 39443104 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab

docs: blockdev: convert to ReST

Rename the blockdev documentation files to ReST, add an
index for them and adjust in order to produce a nice html
output via the Sphinx build system.

The drbd sub-directory contains some graphs and data flows.
Add those too to the documentation.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+samsung@kernel.org>
parent e0ae1544
......@@ -1249,7 +1249,7 @@
See also Documentation/fault-injection/.
floppy= [HW]
See Documentation/blockdev/floppy.txt.
See Documentation/blockdev/floppy.rst.
force_pal_cache_flush
[IA-64] Avoid check_sal_cache_flush which may hang on
......@@ -2234,7 +2234,7 @@
memblock=debug [KNL] Enable memblock debug messages.
load_ramdisk= [RAM] List of ramdisks to load from floppy
See Documentation/blockdev/ramdisk.txt.
See Documentation/blockdev/ramdisk.rst.
lockd.nlm_grace_period=P [NFS] Assign grace period.
Format: <integer>
......@@ -3268,7 +3268,7 @@
pcd. [PARIDE]
See header of drivers/block/paride/pcd.c.
See also Documentation/blockdev/paride.txt.
See also Documentation/blockdev/paride.rst.
pci=option[,option...] [PCI] various PCI subsystem options.
......@@ -3512,7 +3512,7 @@
needed on a platform with proper driver support.
pd. [PARIDE]
See Documentation/blockdev/paride.txt.
See Documentation/blockdev/paride.rst.
pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
boot time.
......@@ -3527,10 +3527,10 @@
and performance comparison.
pf. [PARIDE]
See Documentation/blockdev/paride.txt.
See Documentation/blockdev/paride.rst.
pg. [PARIDE]
See Documentation/blockdev/paride.txt.
See Documentation/blockdev/paride.rst.
pirq= [SMP,APIC] Manual mp-table setup
See Documentation/x86/i386/IO-APIC.rst.
......@@ -3642,7 +3642,7 @@
prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
before loading.
See Documentation/blockdev/ramdisk.txt.
See Documentation/blockdev/ramdisk.rst.
psi= [KNL] Enable or disable pressure stall information
tracking.
......@@ -3664,7 +3664,7 @@
pstore.backend= Specify the name of the pstore backend to use
pt. [PARIDE]
See Documentation/blockdev/paride.txt.
See Documentation/blockdev/paride.rst.
pti= [X86_64] Control Page Table Isolation of user and
kernel address spaces. Disabling this feature
......@@ -3693,7 +3693,7 @@
See Documentation/admin-guide/md.rst.
ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
See Documentation/blockdev/ramdisk.txt.
See Documentation/blockdev/ramdisk.rst.
random.trust_cpu={on,off}
[KNL] Enable or disable trusting the use of the
......
================================
kernel data structure for DRBD-9
================================
This describes the in kernel data structure for DRBD-9. Starting with
Linux v3.14 we are reorganizing DRBD to use this data structure.
......@@ -10,7 +14,7 @@ device is represented by a block device locally.
The DRBD objects are interconnected to form a matrix as depicted below; a
drbd_peer_device object sits at each intersection between a drbd_device and a
drbd_connection:
drbd_connection::
/--------------+---------------+.....+---------------\
| resource | device | | device |
......
.. The here included files are intended to help understand the implementation
Data flows that Relate some functions, and write packets
========================================================
.. kernel-figure:: DRBD-8.3-data-packets.svg
:alt: DRBD-8.3-data-packets.svg
:align: center
.. kernel-figure:: DRBD-data-packets.svg
:alt: DRBD-data-packets.svg
:align: center
Sub graphs of DRBD's state transitions
======================================
.. kernel-figure:: conn-states-8.dot
:alt: conn-states-8.dot
:align: center
.. kernel-figure:: disk-states-8.dot
:alt: disk-states-8.dot
:align: center
.. kernel-figure:: node-states-8.dot
:alt: node-states-8.dot
:align: center
==========================================
Distributed Replicated Block Device - DRBD
==========================================
Description
===========
DRBD is a shared-nothing, synchronously replicated block device. It
is designed to serve as a building block for high availability
......@@ -7,10 +12,8 @@ Description
Please visit http://www.drbd.org to find out more.
The here included files are intended to help understand the implementation
DRBD-8.3-data-packets.svg, DRBD-data-packets.svg
relates some functions, and write packets.
.. toctree::
:maxdepth: 1
conn-states-8.dot, disk-states-8.dot, node-states-8.dot
The sub graphs of DRBD's state transitions
data-structure-v9
figures
This file describes the floppy driver.
=============
Floppy Driver
=============
FAQ list:
=========
A FAQ list may be found in the fdutils package (see below), and also
A FAQ list may be found in the fdutils package (see below), and also
at <http://fdutils.linux.lu/faq.html>.
LILO configuration options (Thinkpad users, read this)
======================================================
The floppy driver is configured using the 'floppy=' option in
The floppy driver is configured using the 'floppy=' option in
lilo. This option can be typed at the boot prompt, or entered in the
lilo configuration file.
Example: If your kernel is called linux-2.6.9, type the following line
at the lilo boot prompt (if you have a thinkpad):
Example: If your kernel is called linux-2.6.9, type the following line
at the lilo boot prompt (if you have a thinkpad)::
linux-2.6.9 floppy=thinkpad
You may also enter the following line in /etc/lilo.conf, in the description
of linux-2.6.9:
of linux-2.6.9::
append = "floppy=thinkpad"
Several floppy related options may be given, example:
Several floppy related options may be given, example::
linux-2.6.9 floppy=daring floppy=two_fdc
append = "floppy=daring floppy=two_fdc"
If you give options both in the lilo config file and on the boot
If you give options both in the lilo config file and on the boot
prompt, the option strings of both places are concatenated, the boot
prompt options coming last. That's why there are also options to
restore the default behavior.
......@@ -38,21 +40,23 @@ restore the default behavior.
Module configuration options
============================
If you use the floppy driver as a module, use the following syntax:
modprobe floppy floppy="<options>"
If you use the floppy driver as a module, use the following syntax::
modprobe floppy floppy="<options>"
Example::
Example:
modprobe floppy floppy="omnibook messages"
If you need certain options enabled every time you load the floppy driver,
you can put:
If you need certain options enabled every time you load the floppy driver,
you can put::
options floppy floppy="omnibook messages"
in a configuration file in /etc/modprobe.d/.
The floppy driver related options are:
The floppy driver related options are:
floppy=asus_pci
Sets the bit mask to allow only units 0 and 1. (default)
......@@ -70,8 +74,7 @@ in a configuration file in /etc/modprobe.d/.
Tells the floppy driver that you have only one floppy controller.
(default)
floppy=two_fdc
floppy=<address>,two_fdc
floppy=two_fdc / floppy=<address>,two_fdc
Tells the floppy driver that you have two floppy controllers.
The second floppy controller is assumed to be at <address>.
This option is not needed if the second controller is at address
......@@ -84,8 +87,7 @@ in a configuration file in /etc/modprobe.d/.
floppy=0,thinkpad
Tells the floppy driver that you don't have a Thinkpad.
floppy=omnibook
floppy=nodma
floppy=omnibook / floppy=nodma
Tells the floppy driver not to use Dma for data transfers.
This is needed on HP Omnibooks, which don't have a workable
DMA channel for the floppy driver. This option is also useful
......@@ -144,14 +146,16 @@ in a configuration file in /etc/modprobe.d/.
described in the physical CMOS), or if your BIOS uses
non-standard CMOS types. The CMOS types are:
0 - Use the value of the physical CMOS
1 - 5 1/4 DD
2 - 5 1/4 HD
3 - 3 1/2 DD
4 - 3 1/2 HD
5 - 3 1/2 ED
6 - 3 1/2 ED
16 - unknown or not installed
== ==================================
0 Use the value of the physical CMOS
1 5 1/4 DD
2 5 1/4 HD
3 3 1/2 DD
4 3 1/2 HD
5 3 1/2 ED
6 3 1/2 ED
16 unknown or not installed
== ==================================
(Note: there are two valid types for ED drives. This is because 5 was
initially chosen to represent floppy *tapes*, and 6 for ED drives.
......@@ -162,8 +166,7 @@ in a configuration file in /etc/modprobe.d/.
Print a warning message when an unexpected interrupt is received.
(default)
floppy=no_unexpected_interrupts
floppy=L40SX
floppy=no_unexpected_interrupts / floppy=L40SX
Don't print a message when an unexpected interrupt is received. This
is needed on IBM L40SX laptops in certain video modes. (There seems
to be an interaction between video and floppy. The unexpected
......@@ -199,47 +202,54 @@ in a configuration file in /etc/modprobe.d/.
Sets the floppy DMA channel to <nr> instead of 2.
floppy=slow
Use PS/2 stepping rate:
" PS/2 floppies have much slower step rates than regular floppies.
Use PS/2 stepping rate::
PS/2 floppies have much slower step rates than regular floppies.
It's been recommended that take about 1/4 of the default speed
in some more extreme cases."
in some more extreme cases.
Supporting utilities and additional documentation:
==================================================
Additional parameters of the floppy driver can be configured at
Additional parameters of the floppy driver can be configured at
runtime. Utilities which do this can be found in the fdutils package.
This package also contains a new version of mtools which allows to
access high capacity disks (up to 1992K on a high density 3 1/2 disk!).
It also contains additional documentation about the floppy driver.
The latest version can be found at fdutils homepage:
http://fdutils.linux.lu
The fdutils releases can be found at:
http://fdutils.linux.lu/download.html
http://www.tux.org/pub/knaff/fdutils/
ftp://metalab.unc.edu/pub/Linux/utils/disk-management/
Reporting problems about the floppy driver
==========================================
If you have a question or a bug report about the floppy driver, mail
If you have a question or a bug report about the floppy driver, mail
me at Alain.Knaff@poboxes.com . If you post to Usenet, preferably use
comp.os.linux.hardware. As the volume in these groups is rather high,
be sure to include the word "floppy" (or "FLOPPY") in the subject
line. If the reported problem happens when mounting floppy disks, be
sure to mention also the type of the filesystem in the subject line.
Be sure to read the FAQ before mailing/posting any bug reports!
Be sure to read the FAQ before mailing/posting any bug reports!
Alain
Alain
Changelog
=========
10-30-2004 : Cleanup, updating, add reference to module configuration.
10-30-2004 :
Cleanup, updating, add reference to module configuration.
James Nelson <james4765@gmail.com>
6-3-2000 : Original Document
6-3-2000 :
Original Document
:orphan:
===========================
The Linux RapidIO Subsystem
===========================
.. toctree::
:maxdepth: 1
floppy
nbd
paride
ramdisk
zram
drbd/index
==================================
Network Block Device (TCP version)
==================================
......@@ -28,4 +29,3 @@ max_part
nbds_max
Number of block devices that should be initialized (default: 16).
Linux and parallel port IDE devices
===================================
Linux and parallel port IDE devices
===================================
PARIDE v1.03 (c) 1997-8 Grant Guenther <grant@torque.net>
1. Introduction
===============
Owing to the simplicity and near universality of the parallel port interface
to personal computers, many external devices such as portable hard-disk,
......@@ -35,17 +37,17 @@ devices. It does not cover parallel port SCSI devices, "ditto" tape
drives or scanners. Many different devices are supported by the
parallel port IDE subsystem, including:
MicroSolutions backpack CD-ROM
MicroSolutions backpack PD/CD
MicroSolutions backpack hard-drives
MicroSolutions backpack 8000t tape drive
SyQuest EZ-135, EZ-230 & SparQ drives
Avatar Shark
Imation Superdisk LS-120
Maxell Superdisk LS-120
FreeCom Power CD
Hewlett-Packard 5GB and 8GB tape drives
Hewlett-Packard 7100 and 7200 CD-RW drives
- MicroSolutions backpack CD-ROM
- MicroSolutions backpack PD/CD
- MicroSolutions backpack hard-drives
- MicroSolutions backpack 8000t tape drive
- SyQuest EZ-135, EZ-230 & SparQ drives
- Avatar Shark
- Imation Superdisk LS-120
- Maxell Superdisk LS-120
- FreeCom Power CD
- Hewlett-Packard 5GB and 8GB tape drives
- Hewlett-Packard 7100 and 7200 CD-RW drives
as well as most of the clone and no-name products on the market.
......@@ -55,11 +57,13 @@ paride module which provides a registry and some common methods for
accessing the parallel ports. The second component is a set of
high-level drivers for each of the different types of supported devices:
=== =============
pd IDE disk
pcd ATAPI CD-ROM
pf ATAPI disk
pt ATAPI tape
pg ATAPI generic
=== =============
(Currently, the pg driver is only used with CD-R drives).
......@@ -69,6 +73,7 @@ for each of the parallel port IDE adapter chips. Thanks to the interest
and encouragement of Linux users from many parts of the world,
support is available for almost all known adapter protocols:
==== ====================================== ====
aten ATEN EH-100 (HK)
bpck Microsolutions backpack (US)
comm DataStor (old-type) "commuter" adapter (TW)
......@@ -83,9 +88,11 @@ support is available for almost all known adapter protocols:
ktti KT Technology PHd adapter (SG)
on20 OnSpec 90c20 (US)
on26 OnSpec 90c26 (US)
==== ====================================== ====
2. Using the PARIDE subsystem
=============================
While configuring the Linux kernel, you may choose either to build
the PARIDE drivers into your kernel, or to build them as modules.
......@@ -105,8 +112,9 @@ subsystem to try them all for you.
For the "brand-name" products listed above, here are the protocol
and high-level drivers that you would use:
================ ============ ====== ========
Manufacturer Model Driver Protocol
================ ============ ====== ========
MicroSolutions CD-ROM pcd bpck
MicroSolutions PD drive pf bpck
MicroSolutions hard-drive pd bpck
......@@ -119,8 +127,10 @@ and high-level drivers that you would use:
Hewlett-Packard 5GB Tape pt epat
Hewlett-Packard 7200e (CD) pcd epat
Hewlett-Packard 7200e (CD-R) pg epat
================ ============ ====== ========
2.1 Configuring built-in drivers
---------------------------------
We recommend that you get to know how the drivers work and how to
configure them as loadable modules, before attempting to compile a
......@@ -143,7 +153,7 @@ protocol identification number and, for some devices, the drive's
chain ID. While your system is booting, a number of messages are
displayed on the console. Like all such messages, they can be
reviewed with the 'dmesg' command. Among those messages will be
some lines like:
some lines like::
paride: bpck registered as protocol 0
paride: epat registered as protocol 1
......@@ -161,7 +171,7 @@ As an example, let's assume that you have a MicroSolutions PD/CD drive
with unit ID number 36 connected to the parallel port at 0x378, a SyQuest
EZ-135 connected to the chained port on the PD/CD drive and also an
Imation Superdisk connected to port 0x278. You could give the following
options on your boot command:
options on your boot command::
pd.drive0=0x378,1 pf.drive0=0x278,1 pf.drive1=0x378,0,36
......@@ -175,18 +185,21 @@ PARPORT parallel port sharing system that is included by the
if you want to use chains of devices on the same parallel port.
2.2 Loading and configuring PARIDE as modules
----------------------------------------------
It is much faster and simpler to get to understand the PARIDE drivers
if you use them as loadable kernel modules.
Note 1: using these drivers with the "kerneld" automatic module loading
system is not recommended for beginners, and is not documented here.
Note 1:
using these drivers with the "kerneld" automatic module loading
system is not recommended for beginners, and is not documented here.
Note 2: if you build PARPORT support as a loadable module, PARIDE must
also be built as loadable modules, and PARPORT must be loaded before the
PARIDE modules.
Note 2:
if you build PARPORT support as a loadable module, PARIDE must
also be built as loadable modules, and PARPORT must be loaded before
the PARIDE modules.
To use PARIDE, you must begin by
To use PARIDE, you must begin by::
insmod paride
......@@ -196,7 +209,7 @@ among other tasks.
Then, load as many of the protocol modules as you think you might need.
As you load each module, it will register the protocols that it supports,
and print a log message to your kernel log file and your console. For
example:
example::
# insmod epat
paride: epat registered as protocol 0
......@@ -211,7 +224,7 @@ individual co-ordinates when you load the driver.
For example, if you had two no-name CD-ROM drives both using the
KingByte KBIC-951A adapter, one on port 0x378 and the other on 0x3bc
you could give the following command:
you could give the following command::
# insmod pcd drive0=0x378,1 drive1=0x3bc,1
......@@ -220,7 +233,7 @@ but check the source files in linux/drivers/block/paride for more
information. (Hopefully someone will write some man pages one day !).
As another example, here's what happens when PARPORT is installed, and
a SyQuest EZ-135 is attached to port 0x378:
a SyQuest EZ-135 is attached to port 0x378::
# insmod paride
paride: version 1.0 installed
......@@ -237,46 +250,47 @@ Note that the last line is the output from the generic partition table
scanner - in this case it reports that it has found a disk with one partition.
2.3 Using a PARIDE device
--------------------------
Once the drivers have been loaded, you can access PARIDE devices in the
same way as their traditional counterparts. You will probably need to
create the device "special files". Here is a simple script that you can
cut to a file and execute:
cut to a file and execute::
#!/bin/bash
#
# mkd -- a script to create the device special files for the PARIDE subsystem
#
function mkdev {
#!/bin/bash
#
# mkd -- a script to create the device special files for the PARIDE subsystem
#
function mkdev {
mknod $1 $2 $3 $4 ; chmod 0660 $1 ; chown root:disk $1
}
#
function pd {
}
#
function pd {
D=$( printf \\$( printf "x%03x" $[ $1 + 97 ] ) )
mkdev pd$D b 45 $[ $1 * 16 ]
for P in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
do mkdev pd$D$P b 45 $[ $1 * 16 + $P ]
done
}
#
cd /dev
#
for u in 0 1 2 3 ; do pd $u ; done
for u in 0 1 2 3 ; do mkdev pcd$u b 46 $u ; done
for u in 0 1 2 3 ; do mkdev pf$u b 47 $u ; done
for u in 0 1 2 3 ; do mkdev pt$u c 96 $u ; done
for u in 0 1 2 3 ; do mkdev npt$u c 96 $[ $u + 128 ] ; done
for u in 0 1 2 3 ; do mkdev pg$u c 97 $u ; done
#
# end of mkd
}
#
cd /dev
#
for u in 0 1 2 3 ; do pd $u ; done
for u in 0 1 2 3 ; do mkdev pcd$u b 46 $u ; done
for u in 0 1 2 3 ; do mkdev pf$u b 47 $u ; done
for u in 0 1 2 3 ; do mkdev pt$u c 96 $u ; done
for u in 0 1 2 3 ; do mkdev npt$u c 96 $[ $u + 128 ] ; done
for u in 0 1 2 3 ; do mkdev pg$u c 97 $u ; done
#
# end of mkd
With the device files and drivers in place, you can access PARIDE devices
like any other Linux device. For example, to mount a CD-ROM in pcd0, use:
like any other Linux device. For example, to mount a CD-ROM in pcd0, use::
mount /dev/pcd0 /cdrom
If you have a fresh Avatar Shark cartridge, and the drive is pda, you
might do something like:
might do something like::
fdisk /dev/pda -- make a new partition table with
partition 1 of type 83
......@@ -289,13 +303,14 @@ might do something like:
Devices like the Imation superdisk work in the same way, except that
they do not have a partition table. For example to make a 120MB
floppy that you could share with a DOS system:
floppy that you could share with a DOS system::
mkdosfs /dev/pf0
mount /dev/pf0 /mnt
2.4 The pf driver
------------------
The pf driver is intended for use with parallel port ATAPI disk
devices. The most common devices in this category are PD drives
......@@ -304,6 +319,7 @@ partitioned. Consequently, the pf driver does not support partitioned
media. This may be changed in a future version of the driver.
2.5 Using the pt driver
------------------------
The pt driver for parallel port ATAPI tape drives is a minimal driver.
It does not yet support many of the standard tape ioctl operations.
......@@ -311,6 +327,7 @@ For best performance, a block size of 32KB should be used. You will
probably want to set the parallel port delay to 0, if you can.
2.6 Using the pg driver
------------------------
The pg driver can be used in conjunction with the cdrecord program
to create CD-ROMs. Please get cdrecord version 1.6.1 or later
......@@ -322,8 +339,10 @@ in EPP mode, try to use "bidirectional" or "PS/2" mode and 1x speeds only.
3. Troubleshooting
==================
3.1 Use EPP mode if you can
----------------------------
The most common problems that people report with the PARIDE drivers
concern the parallel port CMOS settings. At this time, none of the
......@@ -332,6 +351,7 @@ If you are able to do so, please set your parallel port into EPP mode
using your CMOS setup procedure.
3.2 Check the port delay
-------------------------
Some parallel ports cannot reliably transfer data at full speed. To
offset the errors, the PARIDE protocol modules introduce a "port
......@@ -347,6 +367,7 @@ read the comments at the beginning of the driver source files in
linux/drivers/block/paride.
3.3 Some drives need a printer reset
-------------------------------------
There appear to be a number of "noname" external drives on the market
that do not always power up correctly. We have noticed this with some
......@@ -354,7 +375,7 @@ drives based on OnSpec and older Freecom adapters. In these rare cases,
the adapter can often be reinitialised by issuing a "printer reset" on
the parallel port. As the reset operation is potentially disruptive in
multiple device environments, the PARIDE drivers will not do it
automatically. You can however, force a printer reset by doing:
automatically. You can however, force a printer reset by doing::
insmod lp reset=1
rmmod lp
......@@ -364,6 +385,7 @@ your paride drivers as modules, and arrange to do the printer reset
before loading the PARIDE drivers.
3.4 Use the verbose option and dmesg if you need help
------------------------------------------------------
While a lot of testing has gone into these drivers to make them work
as smoothly as possible, problems will arise. If you do have problems,
......@@ -373,7 +395,7 @@ clues, then please make sure that only one drive is hooked to your system,
and that either (a) PARPORT is enabled or (b) no other device driver
is using your parallel port (check in /proc/ioports). Then, load the
appropriate drivers (you can load several protocol modules if you want)
as in:
as in::
# insmod paride
# insmod epat
......@@ -394,12 +416,14 @@ by e-mail to grant@torque.net, or join the linux-parport mailing list
and post your report there.
3.5 For more information or help
---------------------------------
You can join the linux-parport mailing list by sending a mail message
to
to:
linux-parport-request@torque.net
with the single word
with the single word::
subscribe
......@@ -412,6 +436,4 @@ have in your mail headers, when sending mail to the list server.
You might also find some useful information on the linux-parport
web pages (although they are not always up to date) at
http://web.archive.org/web/*/http://www.torque.net/parport/
http://web.archive.org/web/%2E/http://www.torque.net/parport/
==========================================
Using the RAM disk block device with Linux
------------------------------------------
==========================================
Contents:
.. Contents:
1) Overview
2) Kernel Command Line Parameters
......@@ -42,7 +43,7 @@ rescue floppy disk.
2a) Kernel Command Line Parameters
ramdisk_size=N
==============
Size of the ramdisk.
This parameter tells the RAM disk driver to set up RAM disks of N k size. The
default is 4096 (4 MB).
......@@ -50,15 +51,12 @@ default is 4096 (4 MB).
2b) Module parameters
rd_nr
=====
/dev/ramX devices created.
max_part
========
Maximum partition number.
rd_size
=======
See ramdisk_size.
3) Using "rdev -r"
......@@ -71,11 +69,11 @@ to 2 MB (2^11) of where to find the RAM disk (this used to be the size). Bit
prompt/wait sequence is to be given before trying to read the RAM disk. Since
the RAM disk dynamically grows as data is being written into it, a size field
is not required. Bits 11 to 13 are not currently used and may as well be zero.
These numbers are no magical secrets, as seen below:
These numbers are no magical secrets, as seen below::
./arch/x86/kernel/setup.c:#define RAMDISK_IMAGE_START_MASK 0x07FF
./arch/x86/kernel/setup.c:#define RAMDISK_PROMPT_FLAG 0x8000
./arch/x86/kernel/setup.c:#define RAMDISK_LOAD_FLAG 0x4000
./arch/x86/kernel/setup.c:#define RAMDISK_IMAGE_START_MASK 0x07FF
./arch/x86/kernel/setup.c:#define RAMDISK_PROMPT_FLAG 0x8000
./arch/x86/kernel/setup.c:#define RAMDISK_LOAD_FLAG 0x4000
Consider a typical two floppy disk setup, where you will have the
kernel on disk one, and have already put a RAM disk image onto disk #2.
......@@ -92,20 +90,23 @@ sequence so that you have a chance to switch floppy disks.
The command line equivalent is: "prompt_ramdisk=1"
Putting that together gives 2^15 + 2^14 + 0 = 49152 for an rdev word.
So to create disk one of the set, you would do:
So to create disk one of the set, you would do::
/usr/src/linux# cat arch/x86/boot/zImage > /dev/fd0
/usr/src/linux# rdev /dev/fd0 /dev/fd0
/usr/src/linux# rdev -r /dev/fd0 49152
If you make a boot disk that has LILO, then for the above, you would use:
If you make a boot disk that has LILO, then for the above, you would use::
append = "ramdisk_start=0 load_ramdisk=1 prompt_ramdisk=1"
Since the default start = 0 and the default prompt = 1, you could use:
Since the default start = 0 and the default prompt = 1, you could use::
append = "load_ramdisk=1"
4) An Example of Creating a Compressed RAM Disk
----------------------------------------------
-----------------------------------------------
To create a RAM disk image, you will need a spare block device to
construct it on. This can be the RAM disk device itself, or an
......@@ -120,11 +121,11 @@ a) Decide on the RAM disk size that you want. Say 2 MB for this example.
Create it by writing to the RAM disk device. (This step is not currently
required, but may be in the future.) It is wise to zero out the
area (esp. for disks) so that maximal compression is achieved for
the unused blocks of the image that you are about to create.
the unused blocks of the image that you are about to create::
dd if=/dev/zero of=/dev/ram0 bs=1k count=2048
b) Make a filesystem on it. Say ext2fs for this example.
b) Make a filesystem on it. Say ext2fs for this example::
mke2fs -vm0 /dev/ram0 2048
......@@ -133,11 +134,11 @@ c) Mount it, copy the files you want to it (eg: /etc/* /dev/* ...)
d) Compress the contents of the RAM disk. The level of compression
will be approximately 50% of the space used by the files. Unused
space on the RAM disk will compress to almost nothing.
space on the RAM disk will compress to almost nothing::
dd if=/dev/ram0 bs=1k count=2048 | gzip -v9 > /tmp/ram_image.gz
e) Put the kernel onto the floppy
e) Put the kernel onto the floppy::
dd if=zImage of=/dev/fd0 bs=1k
......@@ -146,13 +147,13 @@ f) Put the RAM disk image onto the floppy, after the kernel. Use an offset
(possibly larger) kernel onto the same floppy later without overlapping
the RAM disk image. An offset of 400 kB for kernels about 350 kB in
size would be reasonable. Make sure offset+size of ram_image.gz is
not larger than the total space on your floppy (usually 1440 kB).
not larger than the total space on your floppy (usually 1440 kB)::
dd if=/tmp/ram_image.gz of=/dev/fd0 bs=1k seek=400
g) Use "rdev" to set the boot device, RAM disk offset, prompt flag, etc.
For prompt_ramdisk=1, load_ramdisk=1, ramdisk_start=400, one would
have 2^15 + 2^14 + 400 = 49552.
have 2^15 + 2^14 + 400 = 49552::
rdev /dev/fd0 /dev/fd0
rdev -r /dev/fd0 49552
......@@ -160,15 +161,17 @@ g) Use "rdev" to set the boot device, RAM disk offset, prompt flag, etc.
That is it. You now have your boot/root compressed RAM disk floppy. Some
users may wish to combine steps (d) and (f) by using a pipe.
--------------------------------------------------------------------------
Paul Gortmaker 12/95
Changelog:
----------
10-22-04 : Updated to reflect changes in command line options, remove
10-22-04 :
Updated to reflect changes in command line options, remove
obsolete references, general cleanup.
James Nelson (james4765@gmail.com)
12-95 : Original Document
12-95 :
Original Document
========================================
zram: Compressed RAM based block devices
----------------------------------------
========================================
* Introduction
Introduction
============
The zram module creates RAM based block devices named /dev/zram<id>
(<id> = 0, 1, ...). Pages written to these disks are compressed and stored
......@@ -12,9 +14,11 @@ use as swap disks, various caches under /var and maybe many more :)
Statistics for individual zram devices are exported through sysfs nodes at
/sys/block/zram<id>/
* Usage
Usage
=====
There are several ways to configure and manage zram device(-s):
a) using zram and zram_control sysfs attributes
b) using zramctl utility, provided by util-linux (util-linux@vger.kernel.org).
......@@ -22,7 +26,7 @@ In this document we will describe only 'manual' zram configuration steps,
IOW, zram and zram_control sysfs attributes.
In order to get a better idea about zramctl please consult util-linux
documentation, zramctl man-page or `zramctl --help'. Please be informed
documentation, zramctl man-page or `zramctl --help`. Please be informed
that zram maintainers do not develop/maintain util-linux or zramctl, should
you have any questions please contact util-linux@vger.kernel.org
......@@ -30,19 +34,23 @@ Following shows a typical sequence of steps for using zram.
WARNING
=======
For the sake of simplicity we skip error checking parts in most of the
examples below. However, it is your sole responsibility to handle errors.
zram sysfs attributes always return negative values in case of errors.
The list of possible return codes:
-EBUSY -- an attempt to modify an attribute that cannot be changed once
the device has been initialised. Please reset device first;
-ENOMEM -- zram was not able to allocate enough memory to fulfil your
needs;
-EINVAL -- invalid input has been provided.
======== =============================================================
-EBUSY an attempt to modify an attribute that cannot be changed once
the device has been initialised. Please reset device first;
-ENOMEM zram was not able to allocate enough memory to fulfil your
needs;
-EINVAL invalid input has been provided.
======== =============================================================
If you use 'echo', the returned value that is changed by 'echo' utility,
and, in general case, something like:
and, in general case, something like::
echo 3 > /sys/block/zram0/max_comp_streams
if [ $? -ne 0 ];
......@@ -51,7 +59,11 @@ and, in general case, something like:
should suffice.
1) Load Module:
1) Load Module
==============
::
modprobe zram num_devices=4
This creates 4 devices: /dev/zram{0,1,2,3}
......@@ -59,6 +71,8 @@ num_devices parameter is optional and tells zram how many devices should be
pre-created. Default: 1.
2) Set max number of compression streams
========================================
Regardless the value passed to this attribute, ZRAM will always
allocate multiple compression streams - one per online CPUs - thus
allowing several concurrent compression operations. The number of
......@@ -66,16 +80,20 @@ allocated compression streams goes down when some of the CPUs
become offline. There is no single-compression-stream mode anymore,
unless you are running a UP system or has only 1 CPU online.
To find out how many streams are currently available:
To find out how many streams are currently available::
cat /sys/block/zram0/max_comp_streams
3) Select compression algorithm
===============================
Using comp_algorithm device attribute one can see available and
currently selected (shown in square brackets) compression algorithms,
change selected compression algorithm (once the device is initialised
there is no way to change compression algorithm).
Examples:
Examples::
#show supported compression algorithms
cat /sys/block/zram0/comp_algorithm
lzo [lz4]
......@@ -83,20 +101,23 @@ Examples:
#select lzo compression algorithm
echo lzo > /sys/block/zram0/comp_algorithm
For the time being, the `comp_algorithm' content does not necessarily
For the time being, the `comp_algorithm` content does not necessarily
show every compression algorithm supported by the kernel. We keep this
list primarily to simplify device configuration and one can configure
a new device with a compression algorithm that is not listed in
`comp_algorithm'. The thing is that, internally, ZRAM uses Crypto API
`comp_algorithm`. The thing is that, internally, ZRAM uses Crypto API
and, if some of the algorithms were built as modules, it's impossible
to list all of them using, for instance, /proc/crypto or any other
method. This, however, has an advantage of permitting the usage of
custom crypto compression modules (implementing S/W or H/W compression).
4) Set Disksize
===============
Set disk size by writing the value to sysfs node 'disksize'.
The value can be either in bytes or you can use mem suffixes.
Examples:
Examples::
# Initialize /dev/zram0 with 50MB disksize
echo $((50*1024*1024)) > /sys/block/zram0/disksize
......@@ -111,10 +132,13 @@ since we expect a 2:1 compression ratio. Note that zram uses about 0.1% of the
size of the disk when not in use so a huge zram is wasteful.
5) Set memory limit: Optional
=============================
Set memory limit by writing the value to sysfs node 'mem_limit'.
The value can be either in bytes or you can use mem suffixes.
In addition, you could change the value in runtime.
Examples:
Examples::
# limit /dev/zram0 with 50MB memory
echo $((50*1024*1024)) > /sys/block/zram0/mem_limit
......@@ -126,7 +150,11 @@ Examples:
# To disable memory limit
echo 0 > /sys/block/zram0/mem_limit
6) Activate:
6) Activate
===========
::
mkswap /dev/zram0
swapon /dev/zram0
......@@ -134,6 +162,7 @@ Examples:
mount /dev/zram1 /tmp
7) Add/remove zram devices
==========================
zram provides a control interface, which enables dynamic (on-demand) device
addition and removal.
......@@ -142,37 +171,44 @@ In order to add a new /dev/zramX device, perform read operation on hot_add
attribute. This will return either new device's device id (meaning that you
can use /dev/zram<id>) or error code.
Example:
Example::
cat /sys/class/zram-control/hot_add
1
To remove the existing /dev/zramX device (where X is a device id)
execute
execute::
echo X > /sys/class/zram-control/hot_remove
8) Stats:
8) Stats
========
Per-device statistics are exported as various nodes under /sys/block/zram<id>/
A brief description of exported device attributes. For more details please
read Documentation/ABI/testing/sysfs-block-zram.
====================== ====== ===============================================
Name access description
---- ------ -----------
====================== ====== ===============================================
disksize RW show and set the device's disk size
initstate RO shows the initialization state of the device
reset WO trigger device reset
mem_used_max WO reset the `mem_used_max' counter (see later)
mem_limit WO specifies the maximum amount of memory ZRAM can use
to store the compressed data
writeback_limit WO specifies the maximum amount of write IO zram can
write out to backing device as 4KB unit
mem_used_max WO reset the `mem_used_max` counter (see later)
mem_limit WO specifies the maximum amount of memory ZRAM can
use to store the compressed data
writeback_limit WO specifies the maximum amount of write IO zram
can write out to backing device as 4KB unit
writeback_limit_enable RW show and set writeback_limit feature
max_comp_streams RW the number of possible concurrent compress operations
max_comp_streams RW the number of possible concurrent compress
operations
comp_algorithm RW show and change the compression algorithm
compact WO trigger memory compaction
debug_stat RO this file is used for zram debugging purposes
backing_dev RW set up backend storage for zram to write out
idle WO mark allocated slot as idle
====================== ====== ===============================================
User space is advised to use the following files to read the device statistics.
......@@ -188,23 +224,31 @@ The stat file represents device's I/O statistics not accounted by block
layer and, thus, not available in zram<id>/stat file. It consists of a
single line of text and contains the following stats separated by
whitespace:
failed_reads the number of failed reads
failed_writes the number of failed writes
invalid_io the number of non-page-size-aligned I/O requests
============= =============================================================
failed_reads The number of failed reads
failed_writes The number of failed writes
invalid_io The number of non-page-size-aligned I/O requests
notify_free Depending on device usage scenario it may account
a) the number of pages freed because of swap slot free
notifications or b) the number of pages freed because of
notifications
b) the number of pages freed because of
REQ_OP_DISCARD requests sent by bio. The former ones are
sent to a swap block device when a swap slot is freed,
which implies that this disk is being used as a swap disk.
The latter ones are sent by filesystem mounted with
discard option, whenever some data blocks are getting
discarded.
============= =============================================================
File /sys/block/zram<id>/mm_stat
The stat file represents device's mm statistics. It consists of a single
line of text and contains the following stats separated by whitespace:
================ =============================================================
orig_data_size uncompressed size of data stored in this disk.
This excludes same-element-filled pages (same_pages) since
no memory is allocated for them.
......@@ -223,24 +267,35 @@ line of text and contains the following stats separated by whitespace:
No memory is allocated for such pages.
pages_compacted the number of pages freed during compaction
huge_pages the number of incompressible pages
================ =============================================================
File /sys/block/zram<id>/bd_stat
The stat file represents device's backing device statistics. It consists of
a single line of text and contains the following stats separated by whitespace:
============== =============================================================
bd_count size of data written in backing device.
Unit: 4K bytes
bd_reads the number of reads from backing device
Unit: 4K bytes
bd_writes the number of writes to backing device
Unit: 4K bytes
============== =============================================================
9) Deactivate
=============
::
9) Deactivate:
swapoff /dev/zram0
umount /dev/zram1
10) Reset:
Write any positive value to 'reset' sysfs node
10) Reset
=========
Write any positive value to 'reset' sysfs node::
echo 1 > /sys/block/zram0/reset
echo 1 > /sys/block/zram1/reset
......@@ -248,33 +303,35 @@ a single line of text and contains the following stats separated by whitespace:
resets the disksize to zero. You must set the disksize again
before reusing the device.
* Optional Feature
Optional Feature
================
= writeback
writeback
---------
With CONFIG_ZRAM_WRITEBACK, zram can write idle/incompressible page
to backing storage rather than keeping it in memory.
To use the feature, admin should set up backing device via
To use the feature, admin should set up backing device via::
"echo /dev/sda5 > /sys/block/zramX/backing_dev"
echo /dev/sda5 > /sys/block/zramX/backing_dev
before disksize setting. It supports only partition at this moment.
If admin want to use incompressible page writeback, they could do via
If admin want to use incompressible page writeback, they could do via::
"echo huge > /sys/block/zramX/write"
echo huge > /sys/block/zramX/write
To use idle page writeback, first, user need to declare zram pages
as idle.
as idle::
"echo all > /sys/block/zramX/idle"
echo all > /sys/block/zramX/idle
From now on, any pages on zram are idle pages. The idle mark
will be removed until someone request access of the block.
IOW, unless there is access request, those pages are still idle pages.
Admin can request writeback of those idle pages at right timing via
Admin can request writeback of those idle pages at right timing via::
"echo idle > /sys/block/zramX/writeback"
echo idle > /sys/block/zramX/writeback
With the command, zram writeback idle pages from memory to the storage.
......@@ -285,7 +342,7 @@ to guarantee storage health for entire product life.
To overcome the concern, zram supports "writeback_limit" feature.
The "writeback_limit_enable"'s default value is 0 so that it doesn't limit
any writeback. IOW, if admin want to apply writeback budget, he should
enable writeback_limit_enable via
enable writeback_limit_enable via::
$ echo 1 > /sys/block/zramX/writeback_limit_enable
......@@ -296,7 +353,7 @@ until admin set the budget via /sys/block/zramX/writeback_limit.
assigned via /sys/block/zramX/writeback_limit is meaninless.)
If admin want to limit writeback as per-day 400M, he could do it
like below.
like below::
$ MB_SHIFT=20
$ 4K_SHIFT=12
......@@ -305,16 +362,16 @@ like below.
$ echo 1 > /sys/block/zram0/writeback_limit_enable
If admin want to allow further write again once the bugdet is exausted,
he could do it like below
he could do it like below::
$ echo $((400<<MB_SHIFT>>4K_SHIFT)) > \
/sys/block/zram0/writeback_limit
If admin want to see remaining writeback budget since he set,
If admin want to see remaining writeback budget since he set::
$ cat /sys/block/zramX/writeback_limit
If admin want to disable writeback limit, he could do
If admin want to disable writeback limit, he could do::
$ echo 0 > /sys/block/zramX/writeback_limit_enable
......@@ -326,25 +383,35 @@ budget in next setting is user's job.
If admin want to measure writeback count in a certain period, he could
know it via /sys/block/zram0/bd_stat's 3rd column.
= memory tracking
memory tracking
===============
With CONFIG_ZRAM_MEMORY_TRACKING, user can know information of the
zram block. It could be useful to catch cold or incompressible
pages of the process with*pagemap.
If you enable the feature, you could see block state via
/sys/kernel/debug/zram/zram0/block_state". The output is as follows,
/sys/kernel/debug/zram/zram0/block_state". The output is as follows::
300 75.033841 .wh.
301 63.806904 s...
302 63.806919 ..hi
First column is zram's block index.
Second column is access time since the system was booted
Third column is state of the block.
(s: same page
w: written page to backing store
h: huge page
i: idle page)
First column
zram's block index.
Second column
access time since the system was booted
Third column
state of the block:
s:
same page
w:
written page to backing store
h:
huge page
i:
idle page
First line of above example says 300th block is accessed at 75.033841sec
and the block's state is huge so it is written back to the backing
......
......@@ -11076,7 +11076,7 @@ M: Josef Bacik <josef@toxicpanda.com>
S: Maintained
L: linux-block@vger.kernel.org
L: nbd@other.debian.org
F: Documentation/blockdev/nbd.txt
F: Documentation/blockdev/nbd.rst
F: drivers/block/nbd.c
F: include/trace/events/nbd.h
F: include/uapi/linux/nbd.h
......@@ -12086,7 +12086,7 @@ PARIDE DRIVERS FOR PARALLEL PORT IDE DEVICES
M: Tim Waugh <tim@cyberelk.net>
L: linux-parport@lists.infradead.org (subscribers-only)
S: Maintained
F: Documentation/blockdev/paride.txt
F: Documentation/blockdev/paride.rst
F: drivers/block/paride/
PARISC ARCHITECTURE
......@@ -13367,7 +13367,7 @@ F: drivers/net/wireless/ralink/rt2x00/
RAMDISK RAM BLOCK DEVICE DRIVER
M: Jens Axboe <axboe@kernel.dk>
S: Maintained
F: Documentation/blockdev/ramdisk.txt
F: Documentation/blockdev/ramdisk.rst
F: drivers/block/brd.c
RANCHU VIRTUAL BOARD FOR MIPS
......@@ -17723,7 +17723,7 @@ R: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
L: linux-kernel@vger.kernel.org
S: Maintained
F: drivers/block/zram/
F: Documentation/blockdev/zram.txt
F: Documentation/blockdev/zram.rst
ZS DECSTATION Z85C30 SERIAL DRIVER
M: "Maciej W. Rozycki" <macro@linux-mips.org>
......
......@@ -31,7 +31,7 @@ config BLK_DEV_FD
If you want to use the floppy disk drive(s) of your PC under Linux,
say Y. Information about this driver, especially important for IBM
Thinkpad users, is contained in
<file:Documentation/blockdev/floppy.txt>.
<file:Documentation/blockdev/floppy.rst>.
That file also contains the location of the Floppy driver FAQ as
well as location of the fdutils package used to configure additional
parameters of the driver at run time.
......@@ -96,7 +96,7 @@ config PARIDE
your computer's parallel port. Most of them are actually IDE devices
using a parallel port IDE adapter. This option enables the PARIDE
subsystem which contains drivers for many of these external drives.
Read <file:Documentation/blockdev/paride.txt> for more information.
Read <file:Documentation/blockdev/paride.rst> for more information.
If you have said Y to the "Parallel-port support" configuration
option, you may share a single port between your printer and other
......@@ -261,7 +261,7 @@ config BLK_DEV_NBD
userland (making server and client physically the same computer,
communicating using the loopback network device).
Read <file:Documentation/blockdev/nbd.txt> for more information,
Read <file:Documentation/blockdev/nbd.rst> for more information,
especially about where to find the server code, which runs in user
space and does not need special kernel support.
......@@ -303,7 +303,7 @@ config BLK_DEV_RAM
during the initial install of Linux.
Note that the kernel command line option "ramdisk=XX" is now obsolete.
For details, read <file:Documentation/blockdev/ramdisk.txt>.
For details, read <file:Documentation/blockdev/ramdisk.rst>.
To compile this driver as a module, choose M here: the
module will be called brd. An alias "rd" has been defined
......
......@@ -4424,7 +4424,7 @@ static int __init floppy_setup(char *str)
pr_cont("\n");
} else
DPRINT("botched floppy option\n");
DPRINT("Read Documentation/blockdev/floppy.txt\n");
DPRINT("Read Documentation/blockdev/floppy.rst\n");
return 0;
}
......
......@@ -12,7 +12,7 @@ config ZRAM
It has several use cases, for example: /tmp storage, use as swap
disks and maybe many more.
See Documentation/blockdev/zram.txt for more information.
See Documentation/blockdev/zram.rst for more information.
config ZRAM_WRITEBACK
bool "Write back incompressible or idle page to backing device"
......@@ -26,7 +26,7 @@ config ZRAM_WRITEBACK
With /sys/block/zramX/{idle,writeback}, application could ask
idle page's writeback to the backing device to save in memory.
See Documentation/blockdev/zram.txt for more information.
See Documentation/blockdev/zram.rst for more information.
config ZRAM_MEMORY_TRACKING
bool "Track zRam block status"
......@@ -36,4 +36,4 @@ config ZRAM_MEMORY_TRACKING
of zRAM. Admin could see the information via
/sys/kernel/debug/zram/zramX/block_state.
See Documentation/blockdev/zram.txt for more information.
See Documentation/blockdev/zram.rst for more information.
......@@ -37,4 +37,4 @@ Commands required for testing:
- mkfs/ mkfs.ext4
For more information please refer:
kernel-source-tree/Documentation/blockdev/zram.txt
kernel-source-tree/Documentation/blockdev/zram.rst
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