40c8ee67cf
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 <leonro@nvidia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.