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Message-ID: <TY2PR06MB3424AB7EAB6AEB779D6EAB1A857C9@TY2PR06MB3424.apcprd06.prod.outlook.com>
Date: Fri, 19 May 2023 06:34:43 +0000
From: Angus Chen <angus.chen@...uarmicro.com>
To: Nick Desaulniers <ndesaulniers@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>
CC: "masahiroy@...nel.org" <masahiroy@...nel.org>,
"vbabka@...e.cz" <vbabka@...e.cz>,
"peterz@...radead.org" <peterz@...radead.org>,
"paulmck@...nel.org" <paulmck@...nel.org>,
"rppt@...nel.org" <rppt@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Al Viro <viro@...iv.linux.org.uk>
Subject: RE: [PATCH] init: Add bdev fs printk if mount_block_root failed
> -----Original Message-----
> From: Nick Desaulniers <ndesaulniers@...gle.com>
> Sent: Friday, May 19, 2023 4:36 AM
> To: Andrew Morton <akpm@...ux-foundation.org>; Angus Chen
> <angus.chen@...uarmicro.com>
> Cc: masahiroy@...nel.org; vbabka@...e.cz; peterz@...radead.org;
> paulmck@...nel.org; rppt@...nel.org; linux-kernel@...r.kernel.org; Al Viro
> <viro@...iv.linux.org.uk>
> Subject: Re: [PATCH] init: Add bdev fs printk if mount_block_root failed
>
> On Thu, May 18, 2023 at 1:02 PM Andrew Morton <akpm@...ux-foundation.org>
> wrote:
> >
> > On Thu, 18 May 2023 11:53:21 +0800 Angus Chen
> <angus.chen@...uarmicro.com> wrote:
> >
> > > Attempt to printk all bdev fstype as root gives the following kernel panic:
> > >
> > > [ 1.729006] VFS: Cannot open root device "vda" or
> unknown-block(253,0): error -19
> > > [ 1.730603] Please append a correct "root=" boot option; here are the
> available partitions:
> > > [ 1.732323] fd00 256000 vda
> > > [ 1.732329] driver: virtio_blk
> > > [ 1.734194] Kernel panic - not syncing: VFS: Unable to mount root fs on
> unknown-block(253,0)
> > > [ 1.734771] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.4.0-rc2+ #53
> > > [ 1.735194] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
> BIOS 1.10.2-1ubuntu1 04/01/2014
> > > [ 1.735772] Call Trace:
> > > [ 1.735950] <TASK>
> > > [ 1.736113] dump_stack_lvl+0x32/0x50
> > > [ 1.736367] panic+0x108/0x310
> > > [ 1.736570] mount_block_root+0x161/0x310
> > > [ 1.736849] ? rdinit_setup+0x40/0x40
> > > [ 1.737088] prepare_namespace+0x10c/0x180
> > > [ 1.737393] kernel_init_freeable+0x354/0x450
> > > [ 1.737707] ? rest_init+0xd0/0xd0
> > > [ 1.737945] kernel_init+0x16/0x130
> > > [ 1.738196] ret_from_fork+0x1f/0x30
> > >
> > > QEMU command line:
> > > "qemu-system-x86_64 -append root=/dev/vda rootfstype=ext4 ..."
> > >
> > > This error is because ext4 is not buildin and request ext4 module fail.
>
> Cool! I'm glad this got picked up; I personally find it confusing when
> trying to start from something like an allnoconfig build then start
> enabling configs then hitting this panic; it's unclear to users that
> they are missing the config for the FS they are trying to load and on
> first glance looks like something much worse is going wrong. In that
> sense, I view this as a win. Thanks for the patch!
Thank you, you are welcome.
>
> Acked-by: Nick Desaulniers <ndesaulniers@...gle.com>
>
> I wish the commit message showed an example of the panic after the
> patch, to contrast the before vs. after.
en ,Did a need to send a v2 or just let it go this time?
The information is print:
[ 1.570841] VFS: Cannot open root device "vda" or unknown-block(253,0): error -19
[ 1.571513] Please append a correct "root=" boot option; here are the available partitions:
[ 1.572056] fd00 256000 vda
[ 1.572058] driver: virtio_blk
[ 1.572525] List of all bdev filesystem:
[ 1.572780] ext2
[ 1.572781]
[ 1.573027] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(253,0)
Or:
[ 1.510467] VFS: Cannot open root device "vda" or unknown-block(253,0): error -19
[ 1.512033] Please append a correct "root=" boot option; here are the available partitions:
[ 1.513724] fd00 256000 vda
[ 1.513731] driver: virtio_blk
[ 1.514280] Can't find any bdev filesystem!
[ 1.514540] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(253,0)
>
> > >
> > > As a hint, printk all the bdev fstype available for prompts.
> > >
> >
> > Seems reasonable. I reworded the changelog a bit:
> >
> > : Booting with the QEMU command line:
> > : "qemu-system-x86_64 -append root=/dev/vda rootfstype=ext4 ..."
> > : will panic if ext4 is not builtin and a request to load the ext4 module
> > : fails.
> > :
> > : [ 1.729006] VFS: Cannot open root device "vda" or unknown-block(253,0):
> error -19
> > : [ 1.730603] Please append a correct "root=" boot option; here are the
> available partitions:
> > : [ 1.732323] fd00 256000 vda
> > : [ 1.732329] driver: virtio_blk
> > : [ 1.734194] Kernel panic - not syncing: VFS: Unable to mount root fs on
> unknown-block(253,0)
> > : [ 1.734771] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.4.0-rc2+ #53
> > : [ 1.735194] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
> BIOS 1.10.2-1ubuntu1 04/01/2014
> > : [ 1.735772] Call Trace:
> > : [ 1.735950] <TASK>
> > : [ 1.736113] dump_stack_lvl+0x32/0x50
> > : [ 1.736367] panic+0x108/0x310
> > : [ 1.736570] mount_block_root+0x161/0x310
> > : [ 1.736849] ? rdinit_setup+0x40/0x40
> > : [ 1.737088] prepare_namespace+0x10c/0x180
> > : [ 1.737393] kernel_init_freeable+0x354/0x450
> > : [ 1.737707] ? rest_init+0xd0/0xd0
> > : [ 1.737945] kernel_init+0x16/0x130
> > : [ 1.738196] ret_from_fork+0x1f/0x30
> > :
> > : As a hint, print all the bdev fstypes which are available.
> >
> > > --- a/init/do_mounts.c
> > > +++ b/init/do_mounts.c
> > > @@ -427,8 +427,19 @@ void __init mount_block_root(char *name, int
> flags)
> > > printk("VFS: Cannot open root device \"%s\" or %s:
> error %d\n",
> > > root_device_name, b, err);
> > > printk("Please append a correct \"root=\" boot option;
> here are the available partitions:\n");
> > > -
> > > printk_all_partitions();
> > > +
> > > + if (root_fs_names)
> > > + num_fs = list_bdev_fs_names(fs_names,
> PAGE_SIZE);
> > > + if (!num_fs)
> > > + pr_err("Can't find any bdev filesystem to be used
> for mount!\n");
> > > + else {
> > > + pr_err("List of all bdev filesystem:\n");
> > > + for (i = 0, p = fs_names; i < num_fs; i++, p +=
> strlen(p)+1)
> > > + pr_err(" %s", p);
> > > + pr_err("\n");
> > > + }
> > > +
> > > panic("VFS: Unable to mount root fs on %s", b);
> > > }
> > > if (!(flags & SB_RDONLY)) {
> >
> > And I added a little fix.
> >
> > --- a/init/do_mounts.c~init-add-bdev-fs-printk-if-mount_block_root-failed-fix
> > +++ a/init/do_mounts.c
> > @@ -434,7 +434,7 @@ retry:
> > if (!num_fs)
> > pr_err("Can't find any bdev filesystem to be
> used for mount!\n");
> > else {
> > - pr_err("List of all bdev filesystem:\n");
> > + pr_err("List of all bdev filesystems:\n");
> > for (i = 0, p = fs_names; i < num_fs; i++, p +=
> strlen(p)+1)
> > pr_err(" %s", p);
> > pr_err("\n");
> > _
> >
> >
> > This function now uses a jumble of printk() and pr_err(). Perhaps
> > someone will go through and rationalize all of this sometime.
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
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