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Diffstat (limited to 'kernel/Documentation/device-mapper/linear.txt')
| -rw-r--r-- | kernel/Documentation/device-mapper/linear.txt | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/kernel/Documentation/device-mapper/linear.txt b/kernel/Documentation/device-mapper/linear.txt new file mode 100644 index 000000000..d5307d380 --- /dev/null +++ b/kernel/Documentation/device-mapper/linear.txt @@ -0,0 +1,61 @@ +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 --getsize $1` linear $1 0" | dmsetup create identity +]] + + +[[ +#!/bin/sh +# Join 2 devices together +size1=`blockdev --getsize $1` +size2=`blockdev --getsize $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 --getsize $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`; +]] |