mirror of
https://github.com/torvalds/linux.git
synced 2024-11-22 12:11:40 +00:00
035641b01e
Just calling wait_for_device_probe() is not enough to ensure that
asynchronously probed block devices are available (E.G. mmc, usb), so
add a "dm-mod.waitfor=<device1>[,..,<deviceN>]" parameter to get
dm-init to explicitly wait for specific block devices before
initializing the tables with logic similar to the rootwait logic that
was introduced with commit cc1ed7542c ("init: wait for
asynchronously scanned block devices").
E.G. with dm-verity on mmc using:
dm-mod.waitfor="PARTLABEL=hash-a,PARTLABEL=root-a"
[ 0.671671] device-mapper: init: waiting for all devices to be available before creating mapped devices
[ 0.671679] device-mapper: init: waiting for device PARTLABEL=hash-a ...
[ 0.710695] mmc0: new HS200 MMC card at address 0001
[ 0.711158] mmcblk0: mmc0:0001 004GA0 3.69 GiB
[ 0.715954] mmcblk0boot0: mmc0:0001 004GA0 partition 1 2.00 MiB
[ 0.722085] mmcblk0boot1: mmc0:0001 004GA0 partition 2 2.00 MiB
[ 0.728093] mmcblk0rpmb: mmc0:0001 004GA0 partition 3 512 KiB, chardev (249:0)
[ 0.738274] mmcblk0: p1 p2 p3 p4 p5 p6 p7
[ 0.751282] device-mapper: init: waiting for device PARTLABEL=root-a ...
[ 0.751306] device-mapper: init: all devices available
[ 0.751683] device-mapper: verity: sha256 using implementation "sha256-generic"
[ 0.759344] device-mapper: ioctl: dm-0 (vroot) is ready
[ 0.766540] VFS: Mounted root (squashfs filesystem) readonly on device 254:0.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
134 lines
4.6 KiB
ReStructuredText
134 lines
4.6 KiB
ReStructuredText
================================
|
|
Early creation of mapped devices
|
|
================================
|
|
|
|
It is possible to configure a device-mapper device to act as the root device for
|
|
your system in two ways.
|
|
|
|
The first is to build an initial ramdisk which boots to a minimal userspace
|
|
which configures the device, then pivot_root(8) in to it.
|
|
|
|
The second is to create one or more device-mappers using the module parameter
|
|
"dm-mod.create=" through the kernel boot command line argument.
|
|
|
|
The format is specified as a string of data separated by commas and optionally
|
|
semi-colons, where:
|
|
|
|
- a comma is used to separate fields like name, uuid, flags and table
|
|
(specifies one device)
|
|
- a semi-colon is used to separate devices.
|
|
|
|
So the format will look like this::
|
|
|
|
dm-mod.create=<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<name>,<uuid>,<minor>,<flags>,<table>[,<table>+]+]
|
|
|
|
Where::
|
|
|
|
<name> ::= The device name.
|
|
<uuid> ::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | ""
|
|
<minor> ::= The device minor number | ""
|
|
<flags> ::= "ro" | "rw"
|
|
<table> ::= <start_sector> <num_sectors> <target_type> <target_args>
|
|
<target_type> ::= "verity" | "linear" | ... (see list below)
|
|
|
|
The dm line should be equivalent to the one used by the dmsetup tool with the
|
|
`--concise` argument.
|
|
|
|
Target types
|
|
============
|
|
|
|
Not all target types are available as there are serious risks in allowing
|
|
activation of certain DM targets without first using userspace tools to check
|
|
the validity of associated metadata.
|
|
|
|
======================= =======================================================
|
|
`cache` constrained, userspace should verify cache device
|
|
`crypt` allowed
|
|
`delay` allowed
|
|
`era` constrained, userspace should verify metadata device
|
|
`flakey` constrained, meant for test
|
|
`linear` allowed
|
|
`log-writes` constrained, userspace should verify metadata device
|
|
`mirror` constrained, userspace should verify main/mirror device
|
|
`raid` constrained, userspace should verify metadata device
|
|
`snapshot` constrained, userspace should verify src/dst device
|
|
`snapshot-origin` allowed
|
|
`snapshot-merge` constrained, userspace should verify src/dst device
|
|
`striped` allowed
|
|
`switch` constrained, userspace should verify dev path
|
|
`thin` constrained, requires dm target message from userspace
|
|
`thin-pool` constrained, requires dm target message from userspace
|
|
`verity` allowed
|
|
`writecache` constrained, userspace should verify cache device
|
|
`zero` constrained, not meant for rootfs
|
|
======================= =======================================================
|
|
|
|
If the target is not listed above, it is constrained by default (not tested).
|
|
|
|
Examples
|
|
========
|
|
An example of booting to a linear array made up of user-mode linux block
|
|
devices::
|
|
|
|
dm-mod.create="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
|
|
|
|
This will boot to a rw dm-linear target of 8192 sectors split across two block
|
|
devices identified by their major:minor numbers. After boot, udev will rename
|
|
this target to /dev/mapper/lroot (depending on the rules). No uuid was assigned.
|
|
|
|
An example of multiple device-mappers, with the dm-mod.create="..." contents
|
|
is shown here split on multiple lines for readability::
|
|
|
|
dm-linear,,1,rw,
|
|
0 32768 linear 8:1 0,
|
|
32768 1024000 linear 8:2 0;
|
|
dm-verity,,3,ro,
|
|
0 1638400 verity 1 /dev/sdc1 /dev/sdc2 4096 4096 204800 1 sha256
|
|
ac87db56303c9c1da433d7209b5a6ef3e4779df141200cbd7c157dcb8dd89c42
|
|
5ebfe87f7df3235b80a117ebc4078e44f55045487ad4a96581d1adb564615b51
|
|
|
|
Other examples (per target):
|
|
|
|
"crypt"::
|
|
|
|
dm-crypt,,8,ro,
|
|
0 1048576 crypt aes-xts-plain64
|
|
babebabebabebabebabebabebabebabebabebabebabebabebabebabebabebabe 0
|
|
/dev/sda 0 1 allow_discards
|
|
|
|
"delay"::
|
|
|
|
dm-delay,,4,ro,0 409600 delay /dev/sda1 0 500
|
|
|
|
"linear"::
|
|
|
|
dm-linear,,,rw,
|
|
0 32768 linear /dev/sda1 0,
|
|
32768 1024000 linear /dev/sda2 0,
|
|
1056768 204800 linear /dev/sda3 0,
|
|
1261568 512000 linear /dev/sda4 0
|
|
|
|
"snapshot-origin"::
|
|
|
|
dm-snap-orig,,4,ro,0 409600 snapshot-origin 8:2
|
|
|
|
"striped"::
|
|
|
|
dm-striped,,4,ro,0 1638400 striped 4 4096
|
|
/dev/sda1 0 /dev/sda2 0 /dev/sda3 0 /dev/sda4 0
|
|
|
|
"verity"::
|
|
|
|
dm-verity,,4,ro,
|
|
0 1638400 verity 1 8:1 8:2 4096 4096 204800 1 sha256
|
|
fb1a5a0f00deb908d8b53cb270858975e76cf64105d412ce764225d53b8f3cfd
|
|
51934789604d1b92399c52e7cb149d1b3a1b74bbbcb103b2a0aaacbed5c08584
|
|
|
|
For setups using device-mapper on top of asynchronously probed block
|
|
devices (MMC, USB, ..), it may be necessary to tell dm-init to
|
|
explicitly wait for them to become available before setting up the
|
|
device-mapper tables. This can be done with the "dm-mod.waitfor="
|
|
module parameter, which takes a list of devices to wait for::
|
|
|
|
dm-mod.waitfor=<device1>[,..,<deviceN>]
|