Distributed Network Block Device 3 --rewrite for Kernel 3.x https://git.openslx.org/dnbd3.git/atom/src/kernel?h=formatting 2021-03-04T07:47:43+00:00 2021-03-04T07:47:43+00:00 Manuel Bentele 2021-03-04T07:47:43+00:00 urn:sha1:2b5631eaa444023043a18ff3985f5a0e7a11436a 2020-11-20T13:19:21+00:00 Simon Rettberg 2020-11-20T13:19:21+00:00 urn:sha1:b4d8353913a2f54a9bce314e84415e868dc096cb Formerly, the request that was about to be received was looked up in the receive queue without removing it, then the request payload was received from the socket while the lock was not being held, and finally, the lock was required again and the request removed from the queue. This is dangrous as another thread can concurrently take the request from the queue while the receive thread reads the payload from the socket, leading to a double-free by calling blk_mq_end_request twice. 2020-11-20T12:47:16+00:00 Simon Rettberg 2020-11-20T12:47:16+00:00 urn:sha1:f4ad97dd38c134be53f4bbb30d9fb9cd2ef19844 2020-11-19T12:48:14+00:00 Simon Rettberg 2020-11-19T12:48:14+00:00 urn:sha1:a1caec1f2bebe09f685716f13d7b55f84d8a8145 Previously disconnect was protected against concurrent calls, but connect wasn't. It was easy to crash the kernel when calling connect and disconnect IOCTLs in a tight loop concurrently. A global lock was introduced to make sure only one caller can change the connection state at a time. dev->connection_lock needs to be aquired when calling dnbd3_net_connect or _disconnect. This atomic_t based locking mechanism should be turned into a mutex in a next step, relying on mutex_trylock for cases where we don't have the cmpxchg-schedule() loop. Along the way it was noticed that the send/receive timeouts don't apply to kernel_connect, which might have been the case in older 3.x kernel versions. A crude workaround using nonblocking connect has been introduced to emulate this, but a clean solution for this is welcomed. Also, devices are now properly closed on module unload. 2020-11-16T08:01:54+00:00 Manuel Bentele 2020-11-16T08:01:54+00:00 urn:sha1:9bd0efee359d5436b3b8433dc76c69315b1126a3 This patch replaces the __VA_OPT__ varadic macro for the C preprocessor with a builtin GCC extension for optional varadic arguments. Based on this change, the dnbd3 Linux kernel module can be also built with GCC 7.5 on a fresh Ubuntu 18.04 with Linux kernel version 4.19.x. 2020-11-10T07:29:18+00:00 Manuel Bentele 2020-11-10T07:29:18+00:00 urn:sha1:ea63e29a34037b91e9b2cc2ec37e43bf302b682d With this change, the dnbd3-client is able to display the selected server (choosen by the Linux kernel module) after successful probing. Therefore, the ioctl call OPEN returns the selected server host as index of the specified dnbd3-server hosts after successful probing. 2020-11-10T06:42:40+00:00 Manuel Bentele 2020-11-10T06:42:40+00:00 urn:sha1:5a430387ffc52d1520e3c6bbc7ef664b282c9644 This patch adds the feature to manually switch the dnbd3-server to a specified server. The switching is implemented by the use of the ioctl call SWITCH. 2020-11-09T06:48:36+00:00 Manuel Bentele 2020-11-09T06:48:36+00:00 urn:sha1:07684ba72271a1307124eb71904f5c5aa1aebe43 This patch completes the changes from the last commit [1] and protects in addition the read-only access to the alternative list of new servers. Otherwise a race condition between ioctl ADD_SRV/REM_SRV (process context) and dnbd3 discover thread would be possible since the 'new_servers_num' field is changed in both contexts. [1] - DNBD3 commit db5a93a43fea2aa3c3bbaf8c48d238e60d834676 2020-11-09T06:16:07+00:00 Manuel Bentele 2020-11-09T06:16:07+00:00 urn:sha1:db5a93a43fea2aa3c3bbaf8c48d238e60d834676 This patch locks the protecting spinlock of the DNBD3 device's new server list. Otherwise a race condition between ioctl ADD_SRV/REM_SRV (process context) and dnbd3 discover thread would be possible. 2020-11-09T05:54:54+00:00 Manuel Bentele 2020-11-09T05:54:54+00:00 urn:sha1:03db52349890088b8ceaec17736bbd2d0769b52a This patch changes the probing logic to select the first available dnbd3-server submitted by the ioctl OPEN call. All other specified dnbd3-servers are added to the alternative server list and do not have to be available.