linux/Documentation/device-mapper/linear.rst
Mauro Carvalho Chehab f0ba43774c docs: convert docs to ReST and rename to *.rst
The conversion is actually:
  - add blank lines and indentation in order to identify paragraphs;
  - fix tables markups;
  - add some lists markups;
  - mark literal blocks;
  - adjust title markups.

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: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-06-14 14:21:04 -06:00

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ReStructuredText

=========
dm-linear
=========
Device-Mapper's "linear" target maps a linear range of the Device-Mapper
device onto a linear range of another device. This is the basic building
block of logical volume managers.
Parameters: <dev path> <offset>
<dev path>:
Full pathname to the underlying block-device, or a
"major:minor" device-number.
<offset>:
Starting sector within the device.
Example scripts
===============
::
#!/bin/sh
# Create an identity mapping for a device
echo "0 `blockdev --getsz $1` linear $1 0" | dmsetup create identity
::
#!/bin/sh
# Join 2 devices together
size1=`blockdev --getsz $1`
size2=`blockdev --getsz $2`
echo "0 $size1 linear $1 0
$size1 $size2 linear $2 0" | dmsetup create joined
::
#!/usr/bin/perl -w
# Split a device into 4M chunks and then join them together in reverse order.
my $name = "reverse";
my $extent_size = 4 * 1024 * 2;
my $dev = $ARGV[0];
my $table = "";
my $count = 0;
if (!defined($dev)) {
die("Please specify a device.\n");
}
my $dev_size = `blockdev --getsz $dev`;
my $extents = int($dev_size / $extent_size) -
(($dev_size % $extent_size) ? 1 : 0);
while ($extents > 0) {
my $this_start = $count * $extent_size;
$extents--;
$count++;
my $this_offset = $extents * $extent_size;
$table .= "$this_start $extent_size linear $dev $this_offset\n";
}
`echo \"$table\" | dmsetup create $name`;