[PATCH v5 01/25] sysfs: export sysfs_remove_file_self()

[PATCH v5 01/25] sysfs: export sysfs_remove_file_self()

[Jack Wang]

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

Function is going to be used in transport over RDMA module
in subsequent patches, so export it to GPL modules.

Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: linux-kernel@vger.kernel.org
[jwang: extend the commit message]
Signed-off-by: Jack Wang <jinpu.wang@cloud.iono.com>
---
 fs/sysfs/file.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 130fc6fbcc03..1ff4672d7746 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -492,6 +492,7 @@ bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
 	kernfs_put(kn);
 	return ret;
 }
+EXPORT_SYMBOL_GPL(sysfs_remove_file_self);
 
 void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
 {
-- 
2.17.1

[PATCH v5 14/25] rtrs: a bit of documentation

[Jack Wang]

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

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

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
---
 .../ABI/testing/sysfs-class-rtrs-client       | 190 ++++++++++++++++++
 .../ABI/testing/sysfs-class-rtrs-server       |  81 ++++++++
 drivers/infiniband/ulp/rtrs/README            | 137 +++++++++++++
 3 files changed, 408 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-class-rtrs-client
 create mode 100644 Documentation/ABI/testing/sysfs-class-rtrs-server
 create mode 100644 drivers/infiniband/ulp/rtrs/README

diff --git a/Documentation/ABI/testing/sysfs-class-rtrs-client b/Documentation/ABI/testing/sysfs-class-rtrs-client
new file mode 100644
index 000000000000..8b219cf6c5c4
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-rtrs-client
@@ -0,0 +1,190 @@
+What:		/sys/class/rtrs-client
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+When a user of RTRS API creates a new session, a directory entry with
+the name of that session is created under /sys/class/rtrs-client/<session-name>/
+
+What:		/sys/class/rtrs-client/<session-name>/add_path
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RW, adds a new path (connection) to an existing session. Expected format is the
+following:
+
+  <[source addr,]destination addr>
+
+  *addr ::= [ ip:<ipv4|ipv6> | gid:<gid> ]
+
+What:		/sys/class/rtrs-client/<session-name>/max_reconnect_attempts
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Maximum number reconnect attempts the client should make before giving up
+after connection breaks unexpectedly.
+
+What:		/sys/class/rtrs-client/<session-name>/mp_policy
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Multipath policy specifies which path should be selected on each IO:
+
+   round-robin (0):
+       select path in per CPU round-robin manner.
+
+   min-inflight (1):
+       select path with minimum inflights.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Each path belonging to a given session is listed here by its source and
+destination address. When a new path is added to a session by writing to
+the "add_path" entry, a directory <src@dst> is created.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/state
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RO, Contains "connected" if the session is connected to the peer and fully
+functional.  Otherwise the file contains "disconnected"
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/reconnect
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Write "1" to the file in order to reconnect the path.
+Operation is blocking and returns 0 if reconnect was successful.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/disconnect
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Write "1" to the file in order to disconnect the path.
+Operation blocks until RTRS path is disconnected.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/remove_path
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Write "1" to the file in order to disconnected and remove the path
+from the session.  Operation blocks until the path is disconnected
+and removed from the session.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/hca_name
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RO, Contains the the name of HCA the connection established on.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/hca_port
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RO, Contains the port number of active port traffic is going through.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/src_addr
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RO, Contains the source address of the path
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/dst_addr
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RO, Contains the destination address of the path
+
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/stats/reset_all
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RW, Read will return usage help, write 0 will clear all the statistics.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/stats/sg_entries
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Data to be transferred via RDMA is passed to RTRS as scatter-gather
+list. A scatter-gather list can contain multiple entries.
+Scatter-gather list with less entries require less processing power
+and can therefore transferred faster. The file sg_entries outputs a
+per-CPU distribution table for the number of entries in the
+scatter-gather lists, that were passed to the RTRS API function
+rtrs_clt_request (READ or WRITE).
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/stats/cpu_migration
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RTRS expects that each HCA IRQ is pinned to a separate CPU. If it's
+not the case, the processing of an I/O response could be processed on a
+different CPU than where it was originally submitted.  This file shows
+how many interrupts where generated on a non expected CPU.
+"from:" is the CPU on which the IRQ was expected, but not generated.
+"to:" is the CPU on which the IRQ was generated, but not expected.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/stats/reconnects
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Contains 2 unsigned int values, the first one records number of successful
+reconnects in the path lifetime, the second one records number of failed
+reconnects in the path lifetime.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/stats/rdma_lat
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Latency distribution of RTRS requests.
+The format is:
+   1 ms: <CNT-LAT-READ> <CNT-LAT-WRITE>
+   2 ms: <CNT-LAT-READ> <CNT-LAT-WRITE>
+   4 ms: <CNT-LAT-READ> <CNT-LAT-WRITE>
+   8 ms: <CNT-LAT-READ> <CNT-LAT-WRITE>
+  16 ms: <CNT-LAT-READ> <CNT-LAT-WRITE>
+  ...
+  65536 ms: <CNT-LAT-READ> <CNT-LAT-WRITE>
+  >= 65536 ms: <CNT-LAT-READ> <CNT-LAT-WRITE>
+  maximum ms: <CNT-LAT-READ> <CNT-LAT-WRITE>
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/stats/wc_completion
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Contains 2 unsigned int values, the first one records max number of work
+requests processed in work_completion in session lifetime, the second
+one records average number of work requests processed in work_completion
+in session lifetime.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/stats/rdma
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Contains statistics regarding rdma operations and inflight operations.
+The output consists of 6 values:
+
+<read-count> <read-total-size> <write-count> <write-total-size> \
+<inflights> <failovered>
diff --git a/Documentation/ABI/testing/sysfs-class-rtrs-server b/Documentation/ABI/testing/sysfs-class-rtrs-server
new file mode 100644
index 000000000000..cac2a093d56f
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-rtrs-server
@@ -0,0 +1,81 @@
+What:		/sys/class/rtrs-server
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+When a user of RTRS API creates a new session on a client side, a
+directory entry with the name of that session is created in here.
+
+What:		/sys/class/rtrs-server/<session-name>/paths/
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+When new path is created by writing to "add_path" entry on client side,
+a directory entry named as <source address>@<destination address> is created
+on server.
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/disconnect
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+When "1" is written to the file, the RTRS session is being disconnected.
+Operations is non-blocking and returns control immediately to the caller.
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/hca_name
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RO, Contains the the name of HCA the connection established on.
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/hca_port
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RO, Contains the port number of active port traffic is going through.
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/src_addr
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RO, Contains the source address of the path
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/dst_addr
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RO, Contains the destination address of the path
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/stats/reset_all
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+RW, Read will return usage help, write 0 will clear all the statistics.
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/stats/rdma
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Contains statistics regarding rdma operations and inflight operations.
+The output consists of 5 values:
+<read-count> <read-total-size> <write-count> <write-total-size> <inflights>
+
+What:		/sys/class/rtrs-server/<session-name>/paths/<src@dst>/stats/wc_completion
+Date:		Jan 2020
+KernelVersion:	5.6
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:
+Contains 3 values, the first one is int, records max number of work
+requests processed in work_completion in session lifetime, the second
+one long int records total number of work requests processed in
+work_completion in session lifetime and the 3rd one long int records
+total number of calls to the cq completion handler. Division of 2nd
+number through 3rd gives the average number of completions processed
+in completion handler.
diff --git a/drivers/infiniband/ulp/rtrs/README b/drivers/infiniband/ulp/rtrs/README
new file mode 100644
index 000000000000..e4985070e3c0
--- /dev/null
+++ b/drivers/infiniband/ulp/rtrs/README
@@ -0,0 +1,137 @@
+****************************
+InfiniBand Transport (RTRS)
+****************************
+
+RTRS (InfiniBand Transport) is a reliable high speed transport library
+which provides support to establish optimal number of connections
+between client and server machines using RDMA (InfiniBand, RoCE, iWarp)
+transport. It is optimized to transfer (read/write) IO blocks.
+
+In its core interface it follows the BIO semantics of providing the
+possibility to either write data from an sg list to the remote side
+or to request ("read") data transfer from the remote side into a given
+sg list.
+
+RTRS provides I/O fail-over and load-balancing capabilities by using
+multipath I/O (see "add_path" and "mp_policy" configuration entries).
+
+RTRS is used by the RNBD (Infiniband Network Block Device) modules.
+
+==================
+Transport protocol
+==================
+
+Overview
+--------
+An established connection between a client and a server is called rtrs
+session. A session is associated with a set of memory chunks reserved on the
+server side for a given client for rdma transfer. A session
+consists of multiple paths, each representing a separate physical link
+between client and server. Those are used for load balancing and failover.
+Each path consists of as many connections (QPs) as there are cpus on
+the client.
+
+When processing an incoming rdma write or read request rtrs client uses memory
+chunks reserved for him on the server side. Their number, size and addresses
+need to be exchanged between client and server during the connection
+establishment phase. Apart from the memory related information client needs to
+inform the server about the session name and identify each path and connection
+individually.
+
+On an established session client sends to server write or read messages.
+Server uses immediate field to tell the client which request is being
+acknowledged and for errno. Client uses immediate field to tell the server
+which of the memory chunks has been accessed and at which offset the message
+can be found.
+
+Connection establishment
+------------------------
+
+1. Client starts establishing connections belonging to a path of a session one
+by one via attaching RTRS_MSG_CON_REQ messages to the rdma_connect requests.
+Those include uuid of the session and uuid of the path to be
+established. They are used by the server to find a persisting session/path or
+to create a new one when necessary. The message also contains the protocol
+version and magic for compatibility, total number of connections per session
+(as many as cpus on the client), the id of the current connection and
+the reconnect counter, which is used to resolve the situations where
+client is trying to reconnect a path, while server is still destroying the old
+one.
+
+2. Server accepts the connection requests one by one and attaches
+RTRS_MSG_CONN_RSP messages to the rdma_accept. Apart from magic and
+protocol version, the messages include error code, queue depth supported by
+the server (number of memory chunks which are going to be allocated for that
+session) and the maximum size of one io.
+
+3. After all connections of a path are established client sends to server the
+RTRS_MSG_INFO_REQ message, containing the name of the session. This message
+requests the address information from the server.
+
+4. Server replies to the session info request message with RTRS_MSG_INFO_RSP,
+which contains the addresses and keys of the RDMA buffers allocated for that
+session.
+
+5. Session becomes connected after all paths to be established are connected
+(i.e. steps 1-4 finished for all paths requested for a session)
+
+6. Server and client exchange periodically heartbeat messages (empty rdma
+messages with an immediate field) which are used to detect a crash on remote
+side or network outage in an absence of IO.
+
+7. On any RDMA related error or in the case of a heartbeat timeout, the
+corresponding path is disconnected, all the inflight IO are failed over to a
+healthy path, if any, and the reconnect mechanism is triggered.
+
+CLT                                     SRV
+*for each connection belonging to a path and for each path:
+RTRS_MSG_CON_REQ  ------------------->
+                   <------------------- RTRS_MSG_CON_RSP
+...
+*after all connections are established:
+RTRS_MSG_INFO_REQ ------------------->
+                   <------------------- RTRS_MSG_INFO_RSP
+*heartbeat is started from both sides:
+                   -------------------> [RTRS_HB_MSG_IMM]
+[RTRS_HB_MSG_ACK] <-------------------
+[RTRS_HB_MSG_IMM] <-------------------
+                   -------------------> [RTRS_HB_MSG_ACK]
+
+IO path
+-------
+
+* Write *
+
+1. When processing a write request client selects one of the memory chunks
+on the server side and rdma writes there the user data, user header and the
+RTRS_MSG_RDMA_WRITE message. Apart from the type (write), the message only
+contains size of the user header. The client tells the server which chunk has
+been accessed and at what offset the RTRS_MSG_RDMA_WRITE can be found by
+using the IMM field.
+
+2. When confirming a write request server sends an "empty" rdma message with
+an immediate field. The 32 bit field is used to specify the outstanding
+inflight IO and for the error code.
+
+CLT                                                          SRV
+usr_data + usr_hdr + rtrs_msg_rdma_write -----------------> [RTRS_IO_REQ_IMM]
+[RTRS_IO_RSP_IMM]                        <----------------- (id + errno)
+
+* Read *
+
+1. When processing a read request client selects one of the memory chunks
+on the server side and rdma writes there the user header and the
+RTRS_MSG_RDMA_READ message. This message contains the type (read), size of
+the user header, flags (specifying if memory invalidation is necessary) and the
+list of addresses along with keys for the data to be read into.
+
+2. When confirming a read request server transfers the requested data first,
+attaches an invalidation message if requested and finally an "empty" rdma
+message with an immediate field. The 32 bit field is used to specify the
+outstanding inflight IO and the error code.
+
+CLT                                           SRV
+usr_hdr + rtrs_msg_rdma_read --------------> [RTRS_IO_REQ_IMM]
+[RTRS_IO_RSP_IMM]            <-------------- usr_data + (id + errno)
+or in case client requested invalidation:
+[RTRS_IO_RSP_IMM_W_INV]      <-------------- usr_data + (INV) + (id + errno)
-- 
2.17.1

[PATCH v5 24/25] rnbd: a bit of documentation

[Jack Wang]

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    |  51 ++++++++
 .../ABI/testing/sysfs-class-rnbd-client       | 117 ++++++++++++++++++
 .../ABI/testing/sysfs-class-rnbd-server       |  57 +++++++++
 drivers/block/rnbd/README                     |  80 ++++++++++++
 4 files changed, 305 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..dea84280291a
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-block-rnbd
@@ -0,0 +1,51 @@
+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..7466a6aa2641
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-rnbd-client
@@ -0,0 +1,117 @@
+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..1faa9faa8ca3
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-rnbd-server
@@ -0,0 +1,57 @@
+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..2134d60ac3ae
--- /dev/null
+++ b/drivers/block/rnbd/README
@@ -0,0 +1,80 @@
+***************************************
+Infiniband Network Block Device (RNBD)
+***************************************
+
+Introduction
+------------
+
+RNBD (InfiniBand 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.
-- 
2.17.1

Re: [PATCH v5 01/25] sysfs: export sysfs_remove_file_self()

[Jinpu Wang]

On Fri, Dec 20, 2019 at 4:51 PM Jack Wang <jinpuwang@gmail.com> wrote:
>
> From: Jack Wang <jinpu.wang@cloud.iono.com>
>
> Function is going to be used in transport over RDMA module
> in subsequent patches, so export it to GPL modules.
>
> Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
> Acked-by: Tejun Heo <tj@kernel.org>
> Cc: linux-kernel@vger.kernel.org
> [jwang: extend the commit message]
> Signed-off-by: Jack Wang <jinpu.wang@cloud.iono.com>
Sorry, I made a mistake, the email address was wrong, should be cloud.ionos.com,
I've fixed it locally, it will be fixed next round if necessary.

Regards,
Jack Wang