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authorPeter Korsgaard <peter@korsgaard.com>2022-11-16 07:16:56 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-07-23 13:49:38 +0200
commitbe19cb67165143212c6e136de200d26dce5b5ee6 (patch)
treee245e2d5047439c85f7b020696605619faf86436 /Documentation
parente30128926a0f89c04646ecedb0ca3702b04555e1 (diff)
downloadlinux-be19cb67165143212c6e136de200d26dce5b5ee6.tar.gz
dm init: add dm-mod.waitfor to wait for asynchronously probed block devices
commit 035641b01e72af4f6c6cf22a4bdb5d7dfc4e8e8e upstream.

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  cc1ed7542c8c ("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>
Cc: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/device-mapper/dm-init.rst8
1 files changed, 8 insertions, 0 deletions
diff --git a/Documentation/admin-guide/device-mapper/dm-init.rst b/Documentation/admin-guide/device-mapper/dm-init.rst
index e5242ff17e9b..981d6a907699 100644
--- a/Documentation/admin-guide/device-mapper/dm-init.rst
+++ b/Documentation/admin-guide/device-mapper/dm-init.rst
@@ -123,3 +123,11 @@ Other examples (per target):
     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>]