From: Leon Romanovsky <[email protected]>
Attempt to mount 9p file system as root gives the following kernel panic:
9pnet_virtio: no channels available for device root
Kernel panic - not syncing: VFS: Unable to mount root "root" (9p), err=-2
CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.15.0-rc1+ #127
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
Call Trace:
dump_stack_lvl+0x45/0x59
panic+0x1e2/0x44b
? __warn_printk+0xf3/0xf3
? free_unref_page+0x2d4/0x4a0
? trace_hardirqs_on+0x32/0x120
? free_unref_page+0x2d4/0x4a0
mount_root+0x189/0x1e0
prepare_namespace+0x136/0x165
kernel_init_freeable+0x3b8/0x3cb
? rest_init+0x2e0/0x2e0
kernel_init+0x19/0x130
ret_from_fork+0x1f/0x30
Kernel Offset: disabled
---[ end Kernel panic - not syncing: VFS: Unable to mount root "root" (9p), err=-2 ]---
QEMU command line:
"qemu-system-x86_64 -append root=/dev/root rw rootfstype=9p rootflags=trans=virtio ..."
This error is because root_device_name is truncated in prepare_namespace() from
being "/dev/root" to be "root" prior to call to mount_nodev_root().
As a solution, don't treat errors in mount_nodev_root() as errors that
require panics and allow failback to the mount flow that existed before
patch citied in Fixes tag.
Fixes: f9259be6a9e7 ("init: allow mounting arbitrary non-blockdevice filesystems as root")
Signed-off-by: Leon Romanovsky <[email protected]>
---
I'm not sure if this is the right thing to do, but it works for me.
---
init/do_mounts.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 2ed30ff6c906..b423ea7dcc6b 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -553,9 +553,6 @@ static int __init mount_nodev_root(void)
root_mount_data);
if (!err)
break;
- if (err != -EACCES && err != -EINVAL)
- panic("VFS: Unable to mount root \"%s\" (%s), err=%d\n",
- root_device_name, fstype, err);
}
free_page((unsigned long)fs_names);
--
2.31.1
Looks good,
Reviewed-by: Christoph Hellwig <[email protected]>
On Sun, Sep 19, 2021 at 08:46:39AM +0300, Leon Romanovsky wrote:
> On Tue, Sep 14, 2021 at 12:12:10PM +0300, Leon Romanovsky wrote:
> > From: Leon Romanovsky <[email protected]>
> >
> > Attempt to mount 9p file system as root gives the following kernel panic:
> >
> > 9pnet_virtio: no channels available for device root
> > Kernel panic - not syncing: VFS: Unable to mount root "root" (9p), err=-2
> > CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.15.0-rc1+ #127
> > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
> > Call Trace:
> > dump_stack_lvl+0x45/0x59
> > panic+0x1e2/0x44b
> > ? __warn_printk+0xf3/0xf3
> > ? free_unref_page+0x2d4/0x4a0
> > ? trace_hardirqs_on+0x32/0x120
> > ? free_unref_page+0x2d4/0x4a0
> > mount_root+0x189/0x1e0
> > prepare_namespace+0x136/0x165
> > kernel_init_freeable+0x3b8/0x3cb
> > ? rest_init+0x2e0/0x2e0
> > kernel_init+0x19/0x130
> > ret_from_fork+0x1f/0x30
> > Kernel Offset: disabled
> > ---[ end Kernel panic - not syncing: VFS: Unable to mount root "root" (9p), err=-2 ]---
> >
> > QEMU command line:
> > "qemu-system-x86_64 -append root=/dev/root rw rootfstype=9p rootflags=trans=virtio ..."
> >
> > This error is because root_device_name is truncated in prepare_namespace() from
> > being "/dev/root" to be "root" prior to call to mount_nodev_root().
> >
> > As a solution, don't treat errors in mount_nodev_root() as errors that
> > require panics and allow failback to the mount flow that existed before
> > patch citied in Fixes tag.
> >
> > Fixes: f9259be6a9e7 ("init: allow mounting arbitrary non-blockdevice filesystems as root")
> > Signed-off-by: Leon Romanovsky <[email protected]>
> > ---
> > I'm not sure if this is the right thing to do, but it works for me.
> > ---
> > init/do_mounts.c | 3 ---
> > 1 file changed, 3 deletions(-)
>
> Hi,
>
> I assume that after Christoph gave his ROB [1], the patch is ok.
> Should I do anything else in order to progress with merging it?
Sits in the local pile; will go to Linus tomorrow...
On Tue, Sep 14, 2021 at 12:12:10PM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <[email protected]>
>
> Attempt to mount 9p file system as root gives the following kernel panic:
>
> 9pnet_virtio: no channels available for device root
> Kernel panic - not syncing: VFS: Unable to mount root "root" (9p), err=-2
> CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.15.0-rc1+ #127
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
> Call Trace:
> dump_stack_lvl+0x45/0x59
> panic+0x1e2/0x44b
> ? __warn_printk+0xf3/0xf3
> ? free_unref_page+0x2d4/0x4a0
> ? trace_hardirqs_on+0x32/0x120
> ? free_unref_page+0x2d4/0x4a0
> mount_root+0x189/0x1e0
> prepare_namespace+0x136/0x165
> kernel_init_freeable+0x3b8/0x3cb
> ? rest_init+0x2e0/0x2e0
> kernel_init+0x19/0x130
> ret_from_fork+0x1f/0x30
> Kernel Offset: disabled
> ---[ end Kernel panic - not syncing: VFS: Unable to mount root "root" (9p), err=-2 ]---
>
> QEMU command line:
> "qemu-system-x86_64 -append root=/dev/root rw rootfstype=9p rootflags=trans=virtio ..."
>
> This error is because root_device_name is truncated in prepare_namespace() from
> being "/dev/root" to be "root" prior to call to mount_nodev_root().
>
> As a solution, don't treat errors in mount_nodev_root() as errors that
> require panics and allow failback to the mount flow that existed before
> patch citied in Fixes tag.
>
> Fixes: f9259be6a9e7 ("init: allow mounting arbitrary non-blockdevice filesystems as root")
> Signed-off-by: Leon Romanovsky <[email protected]>
> ---
> I'm not sure if this is the right thing to do, but it works for me.
> ---
> init/do_mounts.c | 3 ---
> 1 file changed, 3 deletions(-)
Hi,
I assume that after Christoph gave his ROB [1], the patch is ok.
Should I do anything else in order to progress with merging it?
Thanks
[1] https://lore.kernel.org/all/[email protected]/
On Sun, Sep 19, 2021 at 06:08:44AM +0000, Al Viro wrote:
> On Sun, Sep 19, 2021 at 08:46:39AM +0300, Leon Romanovsky wrote:
> > On Tue, Sep 14, 2021 at 12:12:10PM +0300, Leon Romanovsky wrote:
> > > From: Leon Romanovsky <[email protected]>
> > >
> > > Attempt to mount 9p file system as root gives the following kernel panic:
> > >
> > > 9pnet_virtio: no channels available for device root
> > > Kernel panic - not syncing: VFS: Unable to mount root "root" (9p), err=-2
> > > CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.15.0-rc1+ #127
> > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
> > > Call Trace:
> > > dump_stack_lvl+0x45/0x59
> > > panic+0x1e2/0x44b
> > > ? __warn_printk+0xf3/0xf3
> > > ? free_unref_page+0x2d4/0x4a0
> > > ? trace_hardirqs_on+0x32/0x120
> > > ? free_unref_page+0x2d4/0x4a0
> > > mount_root+0x189/0x1e0
> > > prepare_namespace+0x136/0x165
> > > kernel_init_freeable+0x3b8/0x3cb
> > > ? rest_init+0x2e0/0x2e0
> > > kernel_init+0x19/0x130
> > > ret_from_fork+0x1f/0x30
> > > Kernel Offset: disabled
> > > ---[ end Kernel panic - not syncing: VFS: Unable to mount root "root" (9p), err=-2 ]---
> > >
> > > QEMU command line:
> > > "qemu-system-x86_64 -append root=/dev/root rw rootfstype=9p rootflags=trans=virtio ..."
> > >
> > > This error is because root_device_name is truncated in prepare_namespace() from
> > > being "/dev/root" to be "root" prior to call to mount_nodev_root().
> > >
> > > As a solution, don't treat errors in mount_nodev_root() as errors that
> > > require panics and allow failback to the mount flow that existed before
> > > patch citied in Fixes tag.
> > >
> > > Fixes: f9259be6a9e7 ("init: allow mounting arbitrary non-blockdevice filesystems as root")
> > > Signed-off-by: Leon Romanovsky <[email protected]>
> > > ---
> > > I'm not sure if this is the right thing to do, but it works for me.
> > > ---
> > > init/do_mounts.c | 3 ---
> > > 1 file changed, 3 deletions(-)
> >
> > Hi,
> >
> > I assume that after Christoph gave his ROB [1], the patch is ok.
> > Should I do anything else in order to progress with merging it?
>
> Sits in the local pile; will go to Linus tomorrow...
Thanks Al,
I have a question for the next time, is it possible to see the status
of the patches without nagging you?
Thanks