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authorKees Cook <kees+treewide@kernel.org>2026-09-02 15:31:14 -0700
committerKees Cook <kees@kernel.org>2026-09-04 21:37:00 -0700
commit3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d (patch)
treec65086f9bdcd48c6360fb7cb4598bca084da1f32 /Documentation/admin-guide/device-mapper/linear.rst
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treewide: refresh kmalloc_obj() conversionsgrafted
This is another run of the Coccinelle script for converting kmalloc() family of allocations to kmalloc_obj() via the existing rules in scripts/coccinelle/api/kmalloc_objs.cocci This catches both the set of kmalloc() uses added since the first kmalloc_obj() conversions in v7.0 and adds a large group missed in the first pass due to Coccinelle not interacting well with the cleanup.h scoped_...() family of macros[1]. I worked around this with spatch's "--macro-file" argument to a file with all the scoped_...() macros mapped to Coccinelle's YACFE_ITERATOR[2] as that was the closest viable control flow indicator I could find. Build tested allmodconfig on x86, arm64, arm, loongarch, mips, powerpc, riscv, and s390 with no new warnings. Link: https://lore.kernel.org/lkml/202609021314.8A9C0B8@keescook/ [1] Link: https://github.com/coccinelle/coccinelle/blob/master/standard.h [2] Signed-off-by: Kees Cook <kees+treewide@kernel.org>
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+=========
+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`;