dm init: add dm-mod.waitfor to wait for asynchronously probed block devices

2022-12-02T22:37:45Z

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=[,..,]" 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 Signed-off-by: Mike Snitzer

docs: device-mapper: move it to the admin-guide

2019-07-15T14:03:01Z

The DM support describes lots of aspects related to mapped disk partitions from the userspace PoV. Signed-off-by: Mauro Carvalho Chehab

kernel/Documentation/admin-guide/device-mapper/dm-init.rst, branch linux-rolling-stable

dm init: add dm-mod.waitfor to wait for asynchronously probed block devices

docs: device-mapper: move it to the admin-guide