1What:		/sys/class/rnbd-client
2Date:		Feb 2020
3KernelVersion:	5.7
4Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
5Description:	Provide information about RNBD-client.
6		All sysfs files that are not read-only provide the usage information on read:
7
8		Example::
9
10		    # cat /sys/class/rnbd-client/ctl/map_device
11
12		    > Usage: echo "sessname=<name of the rtrs session> path=<[srcaddr,]dstaddr>
13		    > [path=<[srcaddr,]dstaddr>] device_path=<full path on remote side>
14		    > [access_mode=<ro|rw|migration>] > map_device
15		    >
16		    > addr ::= [ ip:<ipv4> | ip:<ipv6> | gid:<gid> ]
17
18What:		/sys/class/rnbd-client/ctl/map_device
19Date:		Feb 2020
20KernelVersion:	5.7
21Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
22Description:	Expected format is the following::
23
24		    sessname=<name of the rtrs session>
25		    path=<[srcaddr,]dstaddr> [path=<[srcaddr,]dstaddr> ...]
26		    device_path=<full path on remote side>
27		    [access_mode=<ro|rw|migration>]
28
29		Where:
30
31		sessname:
32		    accepts a string not bigger than 256 chars, which identifies
33		    a given session on the client and on the server.
34		    I.e. "clt_hostname-srv_hostname" could be a natural choice.
35
36		path:
37		    describes a connection between the client and the server by
38		    specifying destination and, when required, the source address.
39		    The addresses are to be provided in the following format::
40
41			ip:<IPv6>
42			ip:<IPv4>
43			gid:<GID>
44
45		for example::
46
47		    path=ip:10.0.0.66
48
49		The single addr is treated as the destination.
50		The connection will be established to this server from any client IP address.
51
52		::
53
54		    path=ip:10.0.0.66,ip:10.0.1.66
55
56		First addr is the source address and the second is the destination.
57
58		If multiple "path=" options are specified multiple connection
59		will be established and data will be sent according to
60		the selected multipath policy (see RTRS mp_policy sysfs entry description).
61
62		device_path:
63		    Path to the block device on the server side. Path is specified
64		    relative to the directory on server side configured in the
65		    'dev_search_path' module parameter of the rnbd_server.
66		    The rnbd_server prepends the <device_path> received from client
67		    with <dev_search_path> and tries to open the
68		    <dev_search_path>/<device_path> block device.  On success,
69		    a /dev/rnbd<N> device file, a /sys/block/rnbd<N>/
70		    directory and an entry in /sys/class/rnbd-client/ctl/devices
71		    will be created.
72
73		If 'dev_search_path' contains '%SESSNAME%', then each session can
74		have different devices namespace, e.g. server was configured with
75		the following parameter "dev_search_path=/run/rnbd-devs/%SESSNAME%",
76		client has this string "sessname=blya device_path=sda", then server
77		will try to open: /run/rnbd-devs/blya/sda.
78
79		access_mode:
80		    the access_mode parameter specifies if the device is to be
81		    mapped as "ro" read-only or "rw" read-write. The server allows
82		    a device to be exported in rw mode only once. The "migration"
83		    access mode has to be specified if a second mapping in read-write
84		    mode is desired.
85
86		By default "rw" is used.
87
88		Exit Codes:
89
90		If the device is already mapped it will fail with EEXIST. If the input
91		has an invalid format it will return EINVAL. If the device path cannot
92		be found on the server, it will fail with ENOENT.
93
94		Finding device file after mapping
95		---------------------------------
96
97		After mapping, the device file can be found by:
98		o  The symlink /sys/class/rnbd-client/ctl/devices/<device_id>@<session_name>
99		points to /sys/block/<dev-name>. The last part of the symlink destination
100		is the same as the device name.  By extracting the last part of the
101		path the path to the device /dev/<dev-name> can be build.
102
103		* /dev/block/$(cat /sys/class/rnbd-client/ctl/devices/<device_id>@<session_name>/dev)
104
105		How to find the <device_id> of the device is described on the next
106		section.
107
108What:		/sys/class/rnbd-client/ctl/devices/
109Date:		Feb 2020
110KernelVersion:	5.7
111Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
112Description:	For each device mapped on the client a new symbolic link is created as
113		/sys/class/rnbd-client/ctl/devices/<device_id>@<session_name>, which points
114		to the block device created by rnbd (/sys/block/rnbd<N>/).
115		The <device_id> of each device is created as follows:
116
117		- If the 'device_path' provided during mapping contains slashes ("/"),
118		  they are replaced by exclamation mark ("!") and used as as the
119		  <device_id>. Otherwise, the <device_id> will be the same as the
120		  "device_path" provided.
121