[RFC PATCH] md: dm-init: Wait devices if it's not find on first adpet

[Michael Trimarchi <michael@amarulasolutions.com>]

The device driver can be deferrable and can be a race during
the dm-init early. We need to wait all the probe are really finished
in a loop as is done in do_mounts. This is was tested on kernel 5.4
but code seems was not changed since that time

003: imx8mq-usb-phy 381f0040.usb-phy: 381f0040.usb-phy supply vbus not found, using dummy regulator
003: imx8mq-usb-phy 382f0040.usb-phy: 382f0040.usb-phy supply vbus not found, using dummy regulator
003: imx-cpufreq-dt imx-cpufreq-dt: cpu speed grade 5 mkt segment 0 supported-hw 0x20 0x1
003: caam-dma caam-dma: caam dma support with 2 job rings
000: hctosys: unable to open rtc device (rtc0)
000: device-mapper: init: waiting for all devices to be available before creating mapped devices
002: device-mapper: table: 254:0: verity: Data device lookup failed
002: device-mapper: ioctl: error adding target to table
002: crng init done
003: of_cfs_init
003: of_cfs_init: OK
003: Waiting for root device /dev/dm-0...
001: mmc2: new HS400 Enhanced strobe MMC card at address 0001
001: mmcblk2: mmc2:0001 IB2916 14.6 GiB
001: mmcblk2boot0: mmc2:0001 IB2916 partition 1 4.00 MiB
001: mmcblk2boot1: mmc2:0001 IB2916 partition 2 4.00 MiB
001: mmcblk2rpmb: mmc2:0001 IB2916 partition 3 4.00 MiB, chardev (249:0)
001:  mmcblk2: p1 p2 p3 p4 p5 p6 p7 p8 p9 p10 p11
001: VSD_3V3: disabling

with the patch

003: device-mapper: init: waiting for all devices to be available before creating mapped devices

000: device-mapper: table: 254:0: verity: Data device lookup failed
000: device-mapper: ioctl: error adding target to table
002: crng init done
003: device-mapper: init: waiting for all devices to be available before creating mapped devices
003: device-mapper: table: 254:0: verity: Data device lookup failed
003: device-mapper: ioctl: error adding target to table
003: device-mapper: init: waiting for all devices to be available before creating mapped devices
000: device-mapper: table: 254:0: verity: Data device lookup failed
000: device-mapper: ioctl: error adding target to table
002: device-mapper: init: waiting for all devices to be available before creating mapped devices
002: device-mapper: table: 254:0: verity: Data device lookup failed
002: device-mapper: ioctl: error adding target to table
000: device-mapper: init: waiting for all devices to be available before creating mapped devices
000: device-mapper: table: 254:0: verity: Data device lookup failed
000: device-mapper: ioctl: error adding target to table
003: mmc2: new HS400 Enhanced strobe MMC card at address 0001
003: mmcblk2: mmc2:0001 DG4016 14.7 GiB
003: mmcblk2boot0: mmc2:0001 DG4016 partition 1 4.00 MiB
003: mmcblk2boot1: mmc2:0001 DG4016 partition 2 4.00 MiB
003: mmcblk2rpmb: mmc2:0001 DG4016 partition 3 4.00 MiB, chardev (249:0)
003:  mmcblk2: p1 p2 p3 p4 p5 p6 p7 p8 p9 p10 p11
002: device-mapper: init: waiting for all devices to be available before creating mapped devices
003: device-mapper: verity: sha256 using implementation "sha256-caam"
000: device-mapper: ioctl: dm-0 (rootfs) is ready

Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
---
 drivers/md/dm-init.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-init.c b/drivers/md/dm-init.c
index b0c45c6ebe0b..d3b754036484 100644
--- a/drivers/md/dm-init.c
+++ b/drivers/md/dm-init.c
@@ -7,7 +7,9 @@
  * This file is released under the GPLv2.
  */
 
+#include <linux/async.h>
 #include <linux/ctype.h>
+#include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/device-mapper.h>
 #include <linux/init.h>
@@ -267,6 +269,7 @@ static int __init dm_init_init(void)
 	LIST_HEAD(devices);
 	char *str;
 	int r;
+	bool fail = false;
 
 	if (!create)
 		return 0;
@@ -275,6 +278,7 @@ static int __init dm_init_init(void)
 		DMERR("Argument is too big. Limit is %d", DM_MAX_STR_SIZE);
 		return -EINVAL;
 	}
+retry:
 	str = kstrndup(create, DM_MAX_STR_SIZE, GFP_KERNEL);
 	if (!str)
 		return -ENOMEM;
@@ -288,12 +292,21 @@ static int __init dm_init_init(void)
 
 	list_for_each_entry(dev, &devices, list) {
 		if (dm_early_create(&dev->dmi, dev->table,
-				    dev->target_args_array))
+				    dev->target_args_array)) {
+			fail = true;
 			break;
+		}
 	}
+
 out:
 	kfree(str);
 	dm_setup_cleanup(&devices);
+	if (fail) {
+		msleep(5);
+		fail = false;
+		goto retry;
+	}
+
 	return r;
 }
 
-- 
2.25.1