netdev - [PATCH net-next 0/2] Experimental SMB rootfs support

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Message-Id: <20191001171028.23356-1-pc@cjr.nz>
Date:   Tue,  1 Oct 2019 14:10:26 -0300
From:   "Paulo Alcantara (SUSE)" <pc@....nz>
To:     netdev@...r.kernel.org, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org, davem@...emloft.net,
        smfrench@...il.com
Cc:     "Paulo Alcantara (SUSE)" <pc@....nz>
Subject: [PATCH net-next 0/2] Experimental SMB rootfs support

Hi,

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
    1/2).

    (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
Documentation/filesystems/cifs/cifsroot.txt.

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(-)

-- 
2.23.0