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authorHelen Koike <helen.koike@collabora.com>2019-02-21 17:33:34 -0300
committerMike Snitzer <snitzer@redhat.com>2019-03-05 14:53:50 -0500
commit6bbc923dfcf57d6b97388819a7393835664c7a8e (patch)
treef8170ea4b65c3ea347d34332a1a81444d30b9094 /drivers/md/Kconfig
parent70de2cbda8a5d788284469e755f8b097d339c240 (diff)
downloadlinux-6bbc923dfcf57d6b97388819a7393835664c7a8e.tar.bz2
dm: add support to directly boot to a mapped device
Add a "create" module parameter, which allows device-mapper targets to be configured at boot time. This enables early use of DM targets in the boot process (as the root device or otherwise) without the need of an initramfs. The syntax used in the boot param is based on the concise format from the dmsetup tool to follow the rule of least surprise: dmsetup table --concise /dev/mapper/lroot Which is: 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" | ... For example, the following could be added in the boot parameters: dm-mod.create="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0 Only the targets that were tested are allowed and the ones that don't change any block device when the device is create as read-only. For example, mirror and cache targets are not allowed. The rationale behind this is that if the user makes a mistake, choosing the wrong device to be the mirror or the cache can corrupt data. The only targets initially allowed are: * crypt * delay * linear * snapshot-origin * striped * verity Co-developed-by: Will Drewry <wad@chromium.org> Co-developed-by: Kees Cook <keescook@chromium.org> Co-developed-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> Signed-off-by: Helen Koike <helen.koike@collabora.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/Kconfig')
-rw-r--r--drivers/md/Kconfig12
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 3db222509e44..2557f198e175 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -436,6 +436,18 @@ config DM_DELAY
If unsure, say N.
+config DM_INIT
+ bool "DM \"dm-mod.create=\" parameter support"
+ depends on BLK_DEV_DM=y
+ ---help---
+ Enable "dm-mod.create=" parameter to create mapped devices at init time.
+ This option is useful to allow mounting rootfs without requiring an
+ initramfs.
+ See Documentation/device-mapper/dm-init.txt for dm-mod.create="..."
+ format.
+
+ If unsure, say N.
+
config DM_UEVENT
bool "DM uevents"
depends on BLK_DEV_DM