block/rnbd: a bit of documentation (aa4d16e4) · Commits · EulixOS / Software / Kernel

Documentation/ABI/testing/sysfs-block-rnbd

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		What: /sys/block/rnbd<N>/rnbd/unmap_device
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: To unmap a volume, "normal" or "force" has to be written to:
		/sys/block/rnbd<N>/rnbd/unmap_device

		When "normal" is used, the operation will fail with EBUSY if any process
		is using the device. When "force" is used, the device is also unmapped
		when device is in use. All I/Os that are in progress will fail.

		Example:

		# echo "normal" > /sys/block/rnbd0/rnbd/unmap_device

		What: /sys/block/rnbd<N>/rnbd/state
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: The file contains the current state of the block device. The state file
		returns "open" when the device is successfully mapped from the server
		and accepting I/O requests. When the connection to the server gets
		disconnected in case of an error (e.g. link failure), the state file
		returns "closed" and all I/O requests submitted to it will fail with -EIO.

		What: /sys/block/rnbd<N>/rnbd/session
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: RNBD uses RTRS session to transport the data between client and
		server. The entry "session" contains the name of the session, that
		was used to establish the RTRS session. It's the same name that
		was passed as server parameter to the map_device entry.

		What: /sys/block/rnbd<N>/rnbd/mapping_path
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: Contains the path that was passed as "device_path" to the map_device
		operation.

		What: /sys/block/rnbd<N>/rnbd/access_mode
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: Contains the device access mode: ro, rw or migration.

Documentation/ABI/testing/sysfs-class-rnbd-client

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		What: /sys/class/rnbd-client
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: Provide information about RNBD-client.
		All sysfs files that are not read-only provide the usage information on read:

		Example:
		# cat /sys/class/rnbd-client/ctl/map_device

		> Usage: echo "sessname=<name of the rtrs session> path=<[srcaddr,]dstaddr>
		> [path=<[srcaddr,]dstaddr>] device_path=<full path on remote side>
		> [access_mode=<ro\|rw\|migration>] > map_device
		>
		> addr ::= [ ip:<ipv4> \| ip:<ipv6> \| gid:<gid> ]

		What: /sys/class/rnbd-client/ctl/map_device
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: Expected format is the following:

		sessname=<name of the rtrs session>
		path=<[srcaddr,]dstaddr> [path=<[srcaddr,]dstaddr> ...]
		device_path=<full path on remote side>
		[access_mode=<ro\|rw\|migration>]

		Where:

		sessname: accepts a string not bigger than 256 chars, which identifies
		a given session on the client and on the server.
		I.e. "clt_hostname-srv_hostname" could be a natural choice.

		path: describes a connection between the client and the server by
		specifying destination and, when required, the source address.
		The addresses are to be provided in the following format:

		ip:<IPv6>
		ip:<IPv4>
		gid:<GID>

		for example:

		path=ip:10.0.0.66
		The single addr is treated as the destination.
		The connection will be established to this server from any client IP address.

		path=ip:10.0.0.66,ip:10.0.1.66
		First addr is the source address and the second is the destination.

		If multiple "path=" options are specified multiple connection
		will be established and data will be sent according to
		the selected multipath policy (see RTRS mp_policy sysfs entry description).

		device_path: Path to the block device on the server side. Path is specified
		relative to the directory on server side configured in the
		'dev_search_path' module parameter of the rnbd_server.
		The rnbd_server prepends the <device_path> received from client
		with <dev_search_path> and tries to open the
		<dev_search_path>/<device_path> block device. On success,
		a /dev/rnbd<N> device file, a /sys/block/rnbd_client/rnbd<N>/
		directory and an entry in /sys/class/rnbd-client/ctl/devices
		will be created.

		If 'dev_search_path' contains '%SESSNAME%', then each session can
		have different devices namespace, e.g. server was configured with
		the following parameter "dev_search_path=/run/rnbd-devs/%SESSNAME%",
		client has this string "sessname=blya device_path=sda", then server
		will try to open: /run/rnbd-devs/blya/sda.

		access_mode: the access_mode parameter specifies if the device is to be
		mapped as "ro" read-only or "rw" read-write. The server allows
		a device to be exported in rw mode only once. The "migration"
		access mode has to be specified if a second mapping in read-write
		mode is desired.

		By default "rw" is used.

		Exit Codes:

		If the device is already mapped it will fail with EEXIST. If the input
		has an invalid format it will return EINVAL. If the device path cannot
		be found on the server, it will fail with ENOENT.

		Finding device file after mapping
		---------------------------------

		After mapping, the device file can be found by:
		o The symlink /sys/class/rnbd-client/ctl/devices/<device_id>
		points to /sys/block/<dev-name>. The last part of the symlink destination
		is the same as the device name. By extracting the last part of the
		path the path to the device /dev/<dev-name> can be build.

		o /dev/block/$(cat /sys/class/rnbd-client/ctl/devices/<device_id>/dev)

		How to find the <device_id> of the device is described on the next
		section.

		What: /sys/class/rnbd-client/ctl/devices/
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: For each device mapped on the client a new symbolic link is created as
		/sys/class/rnbd-client/ctl/devices/<device_id>, which points
		to the block device created by rnbd (/sys/block/rnbd<N>/).
		The <device_id> of each device is created as follows:

		- If the 'device_path' provided during mapping contains slashes ("/"),
		they are replaced by exclamation mark ("!") and used as as the
		<device_id>. Otherwise, the <device_id> will be the same as the
		"device_path" provided.

Documentation/ABI/testing/sysfs-class-rnbd-server

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		What: /sys/class/rnbd-server
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: provide information about RNBD-server.

		What: /sys/class/rnbd-server/ctl/
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: When a client maps a device, a directory entry with the name of the
		block device is created under /sys/class/rnbd-server/ctl/devices/.

		What: /sys/class/rnbd-server/ctl/devices/<device_name>/block_dev
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: Is a symlink to the sysfs entry of the exported device.

		Example:
		block_dev -> ../../../../class/block/ram0

		What: /sys/class/rnbd-server/ctl/devices/<device_name>/sessions/
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: For each client a particular device is exported to, following directory will be
		created:

		/sys/class/rnbd-server/ctl/devices/<device_name>/sessions/<session-name>/

		When the device is unmapped by that client, the directory will be removed.

		What: /sys/class/rnbd-server/ctl/devices/<device_name>/sessions/<session-name>/read_only
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: Contains '1' if device is mapped read-only, otherwise '0'.

		What: /sys/class/rnbd-server/ctl/devices/<device_name>/sessions/<session-name>/mapping_path
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: Contains the relative device path provided by the user during mapping.

		What: /sys/class/rnbd-server/ctl/devices/<device_name>/sessions/<session-name>/access_mode
		Date: Feb 2020
		KernelVersion: 5.7
		Contact: Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
		Description: Contains the device access mode: ro, rw or migration.

drivers/block/rnbd/README

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		********************************
		RDMA Network Block Device (RNBD)
		********************************

		Introduction
		------------

		RNBD (RDMA Network Block Device) is a pair of kernel modules
		(client and server) that allow for remote access of a block device on
		the server over RTRS protocol using the RDMA (InfiniBand, RoCE, iWARP)
		transport. After being mapped, the remote block devices can be accessed
		on the client side as local block devices.

		I/O is transferred between client and server by the RTRS transport
		modules. The administration of RNBD and RTRS modules is done via
		sysfs entries.

		Requirements
		------------

		RTRS kernel modules

		Quick Start
		-----------

		Server side:
		# modprobe rnbd_server

		Client side:
		# modprobe rnbd_client
		# echo "sessname=blya path=ip:10.50.100.66 device_path=/dev/ram0" > \
		/sys/devices/virtual/rnbd-client/ctl/map_device

		Where "sessname=" is a session name, a string to identify the session
		on client and on server sides; "path=" is a destination IP address or
		a pair of a source and a destination IPs, separated by comma. Multiple
		"path=" options can be specified in order to use multipath (see RTRS
		description for details); "device_path=" is the block device to be
		mapped from the server side. After the session to the server machine is
		established, the mapped device will appear on the client side under
		/dev/rnbd<N>.


		RNBD-Server Module Parameters
		=============================

		dev_search_path
		---------------

		When a device is mapped from the client, the server generates the path
		to the block device on the server side by concatenating dev_search_path
		and the "device_path" that was specified in the map_device operation.

		The default dev_search_path is: "/".

		dev_search_path option can also contain %SESSNAME% in order to provide
		different device namespaces for different sessions. See "device_path"
		option for details.

		============================
		Protocol (rnbd/rnbd-proto.h)
		============================

		1. Before mapping first device from a given server, client sends an
		RNBD_MSG_SESS_INFO to the server. Server responds with
		RNBD_MSG_SESS_INFO_RSP. Currently the messages only contain the protocol
		version for backward compatibility.

		2. Client requests to open a device by sending RNBD_MSG_OPEN message. This
		contains the path to the device and access mode (read-only or writable).
		Server responds to the message with RNBD_MSG_OPEN_RSP. This contains
		a 32 bit device id to be used for IOs and device "geometry" related
		information: side, max_hw_sectors, etc.

		3. Client attaches RNBD_MSG_IO to each IO message send to a device. This
		message contains device id, provided by server in his rnbd_msg_open_rsp,
		sector to be accessed, read-write flags and bi_size.

		4. Client closes a device by sending RNBD_MSG_CLOSE which contains only the
		device id provided by the server.

		=========================================
		Contributors List(in alphabetical order)
		=========================================
		Danil Kipnis <danil.kipnis@profitbricks.com>
		Fabian Holler <mail@fholler.de>
		Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
		Jack Wang <jinpu.wang@profitbricks.com>
		Kleber Souza <kleber.souza@profitbricks.com>
		Lutz Pogrell <lutz.pogrell@cloud.ionos.com>
		Milind Dumbare <Milind.dumbare@gmail.com>
		Roman Penyaev <roman.penyaev@profitbricks.com>