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

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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>
This commit is contained in:
Peter Korsgaard 2022-11-16 07:16:56 +01:00 committed by Mike Snitzer
parent b52c3de84b
commit 035641b01e
2 changed files with 29 additions and 1 deletions
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8
Documentation/admin-guide/device-mapper/dm-init.rst
View File

@ -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>]

22
drivers/md/dm-init.c
View File

@ -8,6 +8,7 @@
*/
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/device-mapper.h>
#include <linux/init.h>
@ -18,12 +19,17 @@
#define DM_MAX_DEVICES 256
#define DM_MAX_TARGETS 256
#define DM_MAX_STR_SIZE 4096
#define DM_MAX_WAITFOR 256
static char *create;
static char *waitfor[DM_MAX_WAITFOR];
/*
* Format: dm-mod.create=<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<name>,<uuid>,<minor>,<flags>,<table>[,<table>+]+]
* Table format: <start_sector> <num_sectors> <target_type> <target_args>
* Block devices to wait for to become available before setting up tables:
* dm-mod.waitfor=<device1>[,..,<deviceN>]
*
* See Documentation/admin-guide/device-mapper/dm-init.rst for dm-mod.create="..." format
* details.
@ -266,7 +272,7 @@ static int __init dm_init_init(void)
struct dm_device *dev;
LIST_HEAD(devices);
char *str;
int r;
int i, r;
if (!create)
return 0;
@ -286,6 +292,17 @@ static int __init dm_init_init(void)
DMINFO("waiting for all devices to be available before creating mapped devices");
wait_for_device_probe();
for (i = 0; i < ARRAY_SIZE(waitfor); i++) {
if (waitfor[i]) {
DMINFO("waiting for device %s ...", waitfor[i]);
while (!dm_get_dev_t(waitfor[i]))
msleep(5);
}
}
if (waitfor[0])
DMINFO("all devices available");
list_for_each_entry(dev, &devices, list) {
if (dm_early_create(&dev->dmi, dev->table,
dev->target_args_array))
@ -301,3 +318,6 @@ late_initcall(dm_init_init);
module_param(create, charp, 0);
MODULE_PARM_DESC(create, "Create a mapped device in early boot");
module_param_array(waitfor, charp, NULL, 0);
MODULE_PARM_DESC(waitfor, "Devices to wait for before setting up tables");