linux/drivers/block/rnbd
Jack Wang 3a21777c6e block/rnbd-clt: avoid module unload race with close confirmation
We had kernel panic, it is caused by unload module and last
close confirmation.

call trace:
[1196029.743127]  free_sess+0x15/0x50 [rtrs_client]
[1196029.743128]  rtrs_clt_close+0x4c/0x70 [rtrs_client]
[1196029.743129]  ? rnbd_clt_unmap_device+0x1b0/0x1b0 [rnbd_client]
[1196029.743130]  close_rtrs+0x25/0x50 [rnbd_client]
[1196029.743131]  rnbd_client_exit+0x93/0xb99 [rnbd_client]
[1196029.743132]  __x64_sys_delete_module+0x190/0x260

And in the crashdump confirmation kworker is also running.
PID: 6943   TASK: ffff9e2ac8098000  CPU: 4   COMMAND: "kworker/4:2"
 #0 [ffffb206cf337c30] __schedule at ffffffff9f93f891
 #1 [ffffb206cf337cc8] schedule at ffffffff9f93fe98
 #2 [ffffb206cf337cd0] schedule_timeout at ffffffff9f943938
 #3 [ffffb206cf337d50] wait_for_completion at ffffffff9f9410a7
 #4 [ffffb206cf337da0] __flush_work at ffffffff9f08ce0e
 #5 [ffffb206cf337e20] rtrs_clt_close_conns at ffffffffc0d5f668 [rtrs_client]
 #6 [ffffb206cf337e48] rtrs_clt_close at ffffffffc0d5f801 [rtrs_client]
 #7 [ffffb206cf337e68] close_rtrs at ffffffffc0d26255 [rnbd_client]
 #8 [ffffb206cf337e78] free_sess at ffffffffc0d262ad [rnbd_client]
 #9 [ffffb206cf337e88] rnbd_clt_put_dev at ffffffffc0d266a7 [rnbd_client]

The problem is both code path try to close same session, which lead to
panic.

To fix it, just skip the sess if the refcount already drop to 0.

Fixes: f7a7a5c228 ("block/rnbd: client: main functionality")
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Reviewed-by: Gioh Kim <gi-oh.kim@cloud.ionos.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-01-08 08:19:18 -07:00
..
Kconfig block/rnbd: Select SG_POOL for RNBD_CLIENT 2021-01-08 08:19:18 -07:00
Makefile block/rnbd: include client and server modules into kernel compilation 2020-05-17 18:57:17 -03:00
README block/rnbd: Adding name to the Contributors List 2021-01-08 08:19:18 -07:00
rnbd-clt-sysfs.c block/rnbd-clt: Fix possible memleak 2020-12-16 14:55:44 -07:00
rnbd-clt.c block/rnbd-clt: avoid module unload race with close confirmation 2021-01-08 08:19:18 -07:00
rnbd-clt.h block/rnbd-clt: Dynamically allocate sglist for rnbd_iu 2020-12-16 14:56:03 -07:00
rnbd-common.c
rnbd-log.h
rnbd-proto.h block/rnbd: Set write-back cache and fua same to the target device 2020-12-16 14:55:59 -07:00
rnbd-srv-dev.c rnbd: no need to set bi_end_io in rnbd_bio_map_kern 2020-08-06 07:30:04 -06:00
rnbd-srv-dev.h rnbd: remove rnbd_dev_submit_io 2020-08-06 07:30:04 -06:00
rnbd-srv-sysfs.c block/rnbd: call kobject_put in the failure path 2020-12-04 09:41:10 -07:00
rnbd-srv.c block/rnbd-srv: Fix use after free in rnbd_srv_sess_dev_force_close 2021-01-08 08:19:18 -07:00
rnbd-srv.h block/rnbd-srv: close a mapped device from server side. 2020-12-04 09:41:10 -07:00

********************************
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>
Swapnil Ingle <ingleswapnil@gmail.com>