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Message-ID: <YkxlTyMFNNdBqFRd@redhat.com>
Date: Tue, 5 Apr 2022 11:50:39 -0400
From: Mike Snitzer <snitzer@...nel.org>
To: Michael Trimarchi <michael@...rulasolutions.com>
Cc: Alasdair Kergon <agk@...hat.com>, dm-devel@...hat.com,
linux-kernel@...r.kernel.org,
Fabio Aiuto <fabio.aiuto@...rulasolutions.com>
Subject: Re: [RFC PATCH] md: dm-init: Wait devices if it's not find on first
adpet
On Fri, Apr 01 2022 at 6:07P -0400,
Michael Trimarchi <michael@...rulasolutions.com> wrote:
> 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@...rulasolutions.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
>
I'm cannot take this as proposed.
If you're going to do something like this, the retries need to be
bounded. And retry should only be possible for select cases
(e.g. "verity: Data device lookup failed", which is emitted due to
dm_get_device failure with a return -ENODEV).
So please narrow this as much as possible (by only allowing retry if
-ENODEV) and bound the retries to a finite amount.. 5? 10? 20? *shrug*
And please take care to use variable names that are more appropriate
("fail" is not one of them when you're writing retry code)
Mike
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