[PATCH net-next 0/2] Experimental SMB rootfs support
Paulo Alcantara (SUSE)
pc at cjr.nz
Tue Oct 1 17:10:26 UTC 2019
This patch series enables Linux to mount root file systems over the
network by utilizing SMB protocol.
Upstream commit 8eecd1c2e5bc ("cifs: Add support for root file
systems") introduced a new CONFIG_CIFS_ROOT option, a virtual device
(Root_CIFS) and a kernel cmdline parameter "cifsroot=" which tells the
kernel to actually mount the root filesystem over a SMB share.
The feature relies on ipconfig to set up the network prior to mounting
the rootfs, so when it is set along with "cifsroot=" parameter:
(1) cifs_root_setup() parses all necessary data out of "cifsroot="
parameter for the init process know how to mount the SMB rootfs
(e.g. SMB server address, mount options).
(2) If DHCP failed for some reason in ipconfig, we keep retrying
forever as we have nowhere to go for NFS or SMB root
filesystems (see PATCH 2/2). Otherwise go to (3).
(3) mount_cifs_root() is then called by mount_root() (ROOT_DEV ==
Root_CIFS), retrieves early parsed data from (1), then attempt to
mount SMB rootfs by CIFSROOT_RETRY_MAX times at most (see PATCH
(4) If all attempts failed, fall back to floppy drive, otherwise
continue the boot process with rootfs mounted over a SMB share.
My idea was to keep the same behavior of nfsroot - as it seems to work
for most users so far.
For more information on how this feature works, see
Paulo Alcantara (SUSE) (2):
init: Support mounting root file systems over SMB
ipconfig: Handle CONFIG_CIFS_ROOT option
init/do_mounts.c | 49 +++++++++++++++++++++++++++++++++++++++++++++
net/ipv4/ipconfig.c | 10 +++++++--
2 files changed, 57 insertions(+), 2 deletions(-)
More information about the samba-technical