docs: filesystems: convert cifs/cifsroot.txt to ReST

- Add a SPDX header;
- Adjust document title;
- Some whitespace fixes and new line breaks;
- Mark literal blocks as such;
- Add it to filesystems/index.rst.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/28de01ee52283287e4195cf736d7154f122d30d4.1588021877.git.mchehab+huawei@kernel.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/filesystems/cifs/cifsroot.txt → Documentation/filesystems/cifs/cifsroot.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+===========================================
 Mounting root file system via SMB (cifs.ko)
 ===========================================
 
 Written 2019 by Paulo Alcantara <palcantara@suse.de>
+
 Written 2019 by Aurelien Aptel <aaptel@suse.com>
 
 The CONFIG_CIFS_ROOT option enables experimental root file system
@@ -32,7 +36,7 @@ Server configuration
 ====================
 
 To enable SMB1+UNIX extensions you will need to set these global
-settings in Samba smb.conf:
+settings in Samba smb.conf::
 
     [global]
     server min protocol = NT1
@@ -41,12 +45,16 @@ settings in Samba smb.conf:
 Kernel command line
 ===================
 
-root=/dev/cifs
+::
+
+    root=/dev/cifs
 
 This is just a virtual device that basically tells the kernel to mount
 the root file system via SMB protocol.
 
-cifsroot=//<server-ip>/<share>[,options]
+::
+
+    cifsroot=//<server-ip>/<share>[,options]
 
 Enables the kernel to mount the root file system via SMB that are
 located in the <server-ip> and <share> specified in this option.
@@ -65,10 +73,10 @@ options
 Examples
 ========
 
-Export root file system as a Samba share in smb.conf file.
+Export root file system as a Samba share in smb.conf file::
 
-...
-[linux]
+    ...
+    [linux]
 	    path = /path/to/rootfs
 	    read only = no
 	    guest ok = yes
@@ -80,16 +88,16 @@ Export root file system as a Samba share in smb.conf file.
 	    public = yes
 	    create mask = 0777
 	    directory mask = 0777
-...
+    ...
 
-Restart smb service.
+Restart smb service::
 
-# systemctl restart smb
+    # systemctl restart smb
 
 Test it under QEMU on a kernel built with CONFIG_CIFS_ROOT and
-CONFIG_IP_PNP options enabled.
+CONFIG_IP_PNP options enabled::
 
-# qemu-system-x86_64 -enable-kvm -cpu host -m 1024 \
+    # qemu-system-x86_64 -enable-kvm -cpu host -m 1024 \
     -kernel /path/to/linux/arch/x86/boot/bzImage -nographic \
     -append "root=/dev/cifs rw ip=dhcp cifsroot=//10.0.2.2/linux,username=foo,password=bar console=ttyS0 3"
 

Documentation/filesystems/index.rst

@@ -59,6 +59,7 @@ Documentation for filesystem implementations.
    befs
    bfs
    btrfs
+   cifs/cifsroot
    ceph
    cramfs
    debugfs