[PATCH v7 24/25] block/rnbd: a bit of documentation

Jack Wang
2020-01-16T12:59:57Z

From: Jack Wang <jinpu.wang@cloud.ionos.com>

README with description of major sysfs entries, sysfs documentation
are moved to ABI dir as Bart suggested.

Signed-off-by: Danil Kipnis <danil.kipnis@cloud.ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Cc: linux-kernel@vger.kernel.org
---
Documentation/ABI/testing/sysfs-block-rnbd | 46 ++++++++
.../ABI/testing/sysfs-class-rnbd-client | 111 ++++++++++++++++++
.../ABI/testing/sysfs-class-rnbd-server | 50 ++++++++
drivers/block/rnbd/README | 92 +++++++++++++++
4 files changed, 299 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-block-rnbd
create mode 100644 Documentation/ABI/testing/sysfs-class-rnbd-client
create mode 100644 Documentation/ABI/testing/sysfs-class-rnbd-server
create mode 100644 drivers/block/rnbd/README

diff --git a/Documentation/ABI/testing/sysfs-block-rnbd b/Documentation/ABI/testing/sysfs-block-rnbd
new file mode 100644
index 000000000000..1d5053975fa8
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-block-rnbd
@@ -0,0 +1,46 @@
+What: /sys/block/rnbd<N>/rnbd/unmap_device
+Date: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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.
diff --git a/Documentation/ABI/testing/sysfs-class-rnbd-client b/Documentation/ABI/testing/sysfs-class-rnbd-client
new file mode 100644
index 000000000000..0f8ebb23640a
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-rnbd-client
@@ -0,0 +1,111 @@
+What: /sys/class/rnbd-client
+Date: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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.
diff --git a/Documentation/ABI/testing/sysfs-class-rnbd-server b/Documentation/ABI/testing/sysfs-class-rnbd-server
new file mode 100644
index 000000000000..442a060e7be7
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-rnbd-server
@@ -0,0 +1,50 @@
+What: /sys/class/rnbd-server
+Date: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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: Jan 2020
+KernelVersion: 5.6
+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.
diff --git a/drivers/block/rnbd/README b/drivers/block/rnbd/README
new file mode 100644
index 000000000000..83d22f8e1ae7
--- /dev/null
+++ b/drivers/block/rnbd/README
@@ -0,0 +1,92 @@
+********************************
+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 deviec 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>
--
2.17.1