linux-kernel - Re: [PATCH 14/24] init: clear root_wait on all invalid root= strings

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Message-ID: <8c1992bc-110a-4dad-8643-766c14bf6fd4@roeck-us.net>
Date:   Wed, 21 Jun 2023 14:07:13 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Christoph Hellwig <hch@....de>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Mike Snitzer <snitzer@...nel.org>,
        Joern Engel <joern@...ybastard.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Pavel Machek <pavel@....cz>, dm-devel@...hat.com,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-mtd@...ts.infradead.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 14/24] init: clear root_wait on all invalid root= strings

Hi,

On Tue, May 23, 2023 at 09:45:25AM +0200, Christoph Hellwig wrote:
> Instead of only clearing root_wait in devt_from_partuuid when the UUID
> format was invalid, do that in parse_root_device for all strings that
> failed to parse.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>

In linux-next, almost all of my boot tests from usb drives as well
as a few others fail with "Disabling rootwait; root= is invalid."
in the log. Bisect points to this patch.

It can not easily be reverted, but the following change fixes the problem.

--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -413,10 +413,12 @@ static dev_t __init parse_root_device(char *root_device_name)
 
        error = early_lookup_bdev(root_device_name, &dev);
        if (error) {
+#if 0
                if (error == -EINVAL && root_wait) {
                        pr_err("Disabling rootwait; root= is invalid.\n");
                        root_wait = 0;
                }
+#endif
                return 0;
        }
        return dev;

Debugging shows that early_lookup_bdev() indeed returns -EINVAL.
Looking into it further, it turns out that devt_from_devname() returns
-EINVAL for root devices such as
	root=/dev/sda
if the device is not found, making it impossible to rootwait for such
a device (this might for example be a raw USB drive without partitions,
or any qemu drive with format=raw).

Guenter

---
# bad: [15e71592dbae49a674429c618a10401d7f992ac3] Add linux-next specific files for 20230621
# good: [45a3e24f65e90a047bef86f927ebdc4c710edaa1] Linux 6.4-rc7
git bisect start 'HEAD' 'v6.4-rc7'
# good: [e867e67cd55ae460c860ffd896c7fc96add2821c] Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git
git bisect good e867e67cd55ae460c860ffd896c7fc96add2821c
# bad: [0ab4015a11182e2a19c3dd52db85418f370cef39] Merge branch 'for-next' of git://git.kernel.dk/linux-block.git
git bisect bad 0ab4015a11182e2a19c3dd52db85418f370cef39
# good: [901bdf5ea1a836400ee69aa32b04e9c209271ec7] Merge tag 'amd-drm-next-6.5-2023-06-09' of https://gitlab.freedesktop.org/agd5f/linux into drm-next
git bisect good 901bdf5ea1a836400ee69aa32b04e9c209271ec7
# good: [07164956fbc26eff280f3a044a489460ae36413c] Merge branch 'for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394.git
git bisect good 07164956fbc26eff280f3a044a489460ae36413c
# good: [3067e020d361ed346957eb5e253911f7a3e18f59] add snd_soc_{of_}get_dlc()
git bisect good 3067e020d361ed346957eb5e253911f7a3e18f59
# bad: [0dbbd269fb6a8799f312dfc9b1ae1244a144cfc6] Merge branch 'for-6.5/block' into for-next
git bisect bad 0dbbd269fb6a8799f312dfc9b1ae1244a144cfc6
# good: [6c500000af037f74b66dd01b565c8ee1b501cc1b] block: mark bio_add_folio as __must_check
git bisect good 6c500000af037f74b66dd01b565c8ee1b501cc1b
# bad: [1a0ddd56e545b743af510b5a1b8dbdfe7d35cd3b] pktcdvd: replace sscanf() by kstrtoul()
git bisect bad 1a0ddd56e545b743af510b5a1b8dbdfe7d35cd3b
# good: [e3102722ffe77094ba9e7e46380792b3dd8a7abd] init: rename mount_block_root to mount_root_generic
git bisect good e3102722ffe77094ba9e7e46380792b3dd8a7abd
# bad: [d4a28d7defe79006e59293a4b43d518ba8483fb0] dm: remove dm_get_dev_t
git bisect bad d4a28d7defe79006e59293a4b43d518ba8483fb0
# good: [c0c1a7dcb6f5db4500e6574294674213bc24940c] init: move the nfs/cifs/ram special cases out of name_to_dev_t
git bisect good c0c1a7dcb6f5db4500e6574294674213bc24940c
# bad: [702f3189e454b3c3c2f3c99dbf30acf41aab707c] block: move the code to do early boot lookup of block devices to block/
git bisect bad 702f3189e454b3c3c2f3c99dbf30acf41aab707c
# bad: [079caa35f7863cd9958b4555ae873ea4d352a502] init: clear root_wait on all invalid root= strings
git bisect bad 079caa35f7863cd9958b4555ae873ea4d352a502
# good: [cf056a43121559d3642419917d405c3237ded90a] init: improve the name_to_dev_t interface
git bisect good cf056a43121559d3642419917d405c3237ded90a
# first bad commit: [079caa35f7863cd9958b4555ae873ea4d352a502] init: clear root_wait on all invalid root= strings