From mboxrd@z Thu Jan 1 00:00:00 1970 From: shahar.salzman@gmail.com (shahar.salzman) Date: Thu, 25 May 2017 14:06:59 +0300 Subject: NVMeoF: multipath stuck after bringing one ethernet port down In-Reply-To: <656fd267-1e01-b561-fc74-e36c1892d1f9@gmail.com> References: <656fd267-1e01-b561-fc74-e36c1892d1f9@gmail.com> Message-ID: OK, so the indefinite retries are due to the nvme/host/rdma.c:nvme_rdma_queue_rq returning BLK_MQ_RQ_QUEUE_BUSY when the queue is not ready, wouldn't it be better to return BLK_MQ_RQ_QUEUE_ERROR so that the application may handle it? Or alternatively return an error after several retries (per Q or something). I tested a patch (on top of Sagi's) converting the return value to QUEUE_ERROR, and both dd, and multipath -ll return instantly. On 05/23/2017 08:31 PM, shahar.salzman wrote: > I used the patch with my Mellanox OFED (mlnx-nvme-rdma), it patrially > helps but the overall behaviour is still not good... > > If I do a dd (direct_IO) or multipath -ll during the path disconnect, > I get indefinite retries with nearly zero time between retries, until > the path is reconnected, and then dd is completed successfully, paths > come back to life, returning OK status to the process which completes > successfully.I would expect IO to fail after a certain timeout, and > that the retries should be paced somewhat > > If I do an nvme list (blk_execute_rq), then the process stays in D > state (I still see the retries), the block layer (at leasy for this > device) seems to be stuck, and I have to power cycle the server to get > it to work... > > Just a reminder, I am using Mellanox OFED 4.0, and kernel 4.9.6, the > plan here is to upgrade to the latest stable kernel but not sure when > we'll get to it. > > > On 05/18/2017 08:52 AM, shahar.salzman wrote: >> I have seen this too, but was internally investigating it as I am >> running 4.9.6 and not upstream. I will be able to check this patch on >> Sunday/Monday. >> >> On my setup the IOs never complete even after the path is >> reconnected, and the process remains stuck in D state, and the path >> unusable until I power cycle the server. >> >> Some more information, hope it helps: >> >> Dumping the stuck process stack (multipath -ll): >> >> [root at kblock01-knode02 ~]# cat /proc/9715/stack >> [] blk_execute_rq+0x97/0x110 >> [] __nvme_submit_user_cmd+0xca/0x300 [nvme_core] >> [] nvme_submit_user_cmd+0x29/0x30 [nvme_core] >> [] nvme_user_cmd+0x14d/0x180 [nvme_core] >> [] nvme_ioctl+0x7c/0xa0 [nvme_core] >> [] __blkdev_driver_ioctl+0x28/0x30 >> [] blkdev_ioctl+0x131/0x8f0 >> [] block_ioctl+0x3c/0x40 >> [] vfs_ioctl+0x18/0x30 >> [] do_vfs_ioctl+0x161/0x600 >> [] SyS_ioctl+0x92/0xa0 >> [] entry_SYSCALL_64_fastpath+0x1a/0xa9 >> [] 0xffffffffffffffff >> >> Looking at the dissasembly: >> >> 0000000000000170 : >> >> ... >> >> 1fa: e8 00 00 00 00 callq 1ff >> /* Prevent hang_check timer from firing at us during very >> long I/O */ >> hang_check = sysctl_hung_task_timeout_secs; >> if (hang_check) >> while (!wait_for_completion_io_timeout(&wait, >> hang_check * (HZ/2))); >> else >> wait_for_completion_io(&wait); >> 1ff: 4c 89 e7 mov %r12,%rdi >> 202: e8 00 00 00 00 callq 207 >> >> if (rq->errors) >> 207: 83 bb 04 01 00 00 01 cmpl $0x1,0x104(%rbx) >> >> I ran btrace, and it seems that the IO running before the path >> disconnect is properly cleaned, and only the IO running after gets >> stuck (in the btrace example bellow I run both multipath -ll, and a dd): >> >> 259,2 15 27548 4.790727567 8527 I RS 764837376 + 8 [fio] >> 259,2 15 27549 4.790728103 8527 D RS 764837376 + 8 [fio] >> 259,2 15 27550 4.791244566 8527 A R 738007008 + 8 <- >> (253,0) 738007008 >> 259,2 15 27551 4.791245136 8527 I RS 738007008 + 8 [fio] >> 259,2 15 27552 4.791245803 8527 D RS 738007008 + 8 [fio] >> <<<<< From this stage there are no more fio Queue requests, only >> completions >> 259,2 8 9118 4.758116423 8062 C RS 2294539440 + 8 [0] >> 259,2 8 9119 4.758559461 8062 C RS 160307464 + 8 [0] >> 259,2 8 9120 4.759009990 0 C RS 2330623512 + 8 [0] >> 259,2 8 9121 4.759457400 0 C RS 2657710096 + 8 [0] >> 259,2 8 9122 4.759928113 0 C RS 2988256176 + 8 [0] >> 259,2 8 9123 4.760388009 0 C RS 789190936 + 8 [0] >> 259,2 8 9124 4.760835889 0 C RS 2915035352 + 8 [0] >> 259,2 8 9125 4.761304282 0 C RS 2458313624 + 8 [0] >> 259,2 8 9126 4.761779694 0 C RS 2280411456 + 8 [0] >> 259,2 8 9127 4.762286741 0 C RS 2082207376 + 8 [0] >> 259,2 8 9128 4.762783722 0 C RS 2874601688 + 8 [0] >> .... >> 259,2 8 9173 4.785798485 0 C RS 828737568 + 8 [0] >> 259,2 8 9174 4.786301391 0 C RS 229168888 + 8 [0] >> 259,2 8 9175 4.786769105 0 C RS 893604096 + 8 [0] >> 259,2 8 9176 4.787270594 0 C RS 2308778728 + 8 [0] >> 259,2 8 9177 4.787797448 0 C RS 2190029912 + 8 [0] >> 259,2 8 9178 4.788298956 0 C RS 2652012944 + 8 [0] >> 259,2 8 9179 4.788803759 0 C RS 2205242008 + 8 [0] >> 259,2 8 9180 4.789309423 0 C RS 1948528416 + 8 [0] >> 259,2 8 9181 4.789831240 0 C RS 2003421288 + 8 [0] >> 259,2 8 9182 4.790343528 0 C RS 2464964728 + 8 [0] >> 259,2 8 9183 4.790854684 0 C RS 764837376 + 8 [0] >> <<<<<< This is probably where the port had been disconnected >> 259,2 21 7 9.413088410 8574 Q R 0 + 8 [multipathd] >> 259,2 21 8 9.413089387 8574 G R 0 + 8 [multipathd] >> 259,2 21 9 9.413095030 8574 U N [multipathd] 1 >> 259,2 21 10 9.413095367 8574 I RS 0 + 8 [multipathd] >> 259,2 21 11 9.413096534 8574 D RS 0 + 8 [multipathd] >> 259,2 10 1 14.381330190 2016 C RS 738007008 + 8 [7] >> 259,2 21 12 14.381394890 0 R RS 0 + 8 [7] >> 259,2 8 9184 80.500537429 8657 Q R 0 + 8 [dd] >> 259,2 8 9185 80.500540122 8657 G R 0 + 8 [dd] >> 259,2 8 9186 80.500545289 8657 U N [dd] 1 >> 259,2 8 9187 80.500545792 8657 I RS 0 + 8 [dd] >> <<<<<< At this stage, I reconnected the path: >> 259,2 4 1 8381.791090134 11127 Q R 0 + 8 [dd] >> 259,2 4 2 8381.791093611 11127 G R 0 + 8 [dd] >> 259,2 4 3 8381.791098288 11127 U N [dd] 1 >> 259,2 4 4 8381.791098791 11127 I RS 0 + 8 [dd] >> >> >> As I wrote above, I will check the patch on Sunday/Monday. >> >> On 05/17/2017 08:28 PM, Sagi Grimberg wrote: >>> Hi Alex, >>> >>>> I am trying to test failure scenarios of NVMeoF + multipath. I bring >>>> one of ports down and expect to see failed paths using "multipath >>>> -ll". Instead I see that "multipath -ll" get stuck. >>>> >>>> reproduce: >>>> 1. Connected to NVMeoF device through 2 ports. >>>> 2. Bind them with multipath. >>>> 3. Bring one port down (ifconfig eth3 down) >>>> 4. Execute "multipath -ll" command and it will get stuck. >>>> From strace I see that multipath is stuck in io_destroy() during >>>> release of resources. As I understand io_destroy is stuck because of >>>> io_cancel() that failed. And io_cancel() failed because of port that >>>> was disabled in step 3. >>> >>> Hmm, it looks like we do take care of failing fast pending IO, but once >>> we schedule periodic reconnects the request queues are already stopped >>> and new incoming requests may block until we successfully reconnect. >>> >>> I don't have too much time for it at the moment, but here is an >>> untested >>> patch for you to try out: >>> >>> -- >>> [PATCH] nvme-rdma: restart queues after we at error recovery to fast >>> fail incoming io >>> >>> When we encounter an transport/controller errors, error recovery >>> kicks in which performs: >>> 1. stops io/admin queues >>> 2. moves transport queues out of LIVE state >>> 3. fast fail pending io >>> 4. schedule periodic reconnects. >>> >>> But we also need to fast fail incoming IO taht enters after we >>> already scheduled. Given that our queue is not LIVE anymore, simply >>> restart the request queues to fail in .queue_rq >>> >>> Signed-off-by: Sagi Grimberg >>> --- >>> drivers/nvme/host/rdma.c | 20 +++++++++++--------- >>> 1 file changed, 11 insertions(+), 9 deletions(-) >>> >>> diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c >>> index dd1c6deef82f..a0aa2bfb91ee 100644 >>> --- a/drivers/nvme/host/rdma.c >>> +++ b/drivers/nvme/host/rdma.c >>> @@ -753,28 +753,26 @@ static void >>> nvme_rdma_reconnect_ctrl_work(struct work_struct *work) >>> if (ret) >>> goto requeue; >>> >>> - blk_mq_start_stopped_hw_queues(ctrl->ctrl.admin_q, true); >>> - >>> ret = nvmf_connect_admin_queue(&ctrl->ctrl); >>> if (ret) >>> - goto stop_admin_q; >>> + goto requeue; >>> >>> set_bit(NVME_RDMA_Q_LIVE, &ctrl->queues[0].flags); >>> >>> ret = nvme_enable_ctrl(&ctrl->ctrl, ctrl->cap); >>> if (ret) >>> - goto stop_admin_q; >>> + goto requeue; >>> >>> nvme_start_keep_alive(&ctrl->ctrl); >>> >>> if (ctrl->queue_count > 1) { >>> ret = nvme_rdma_init_io_queues(ctrl); >>> if (ret) >>> - goto stop_admin_q; >>> + goto requeue; >>> >>> ret = nvme_rdma_connect_io_queues(ctrl); >>> if (ret) >>> - goto stop_admin_q; >>> + goto requeue; >>> } >>> >>> changed = nvme_change_ctrl_state(&ctrl->ctrl, NVME_CTRL_LIVE); >>> @@ -782,7 +780,6 @@ static void nvme_rdma_reconnect_ctrl_work(struct >>> work_struct *work) >>> ctrl->ctrl.opts->nr_reconnects = 0; >>> >>> if (ctrl->queue_count > 1) { >>> - nvme_start_queues(&ctrl->ctrl); >>> nvme_queue_scan(&ctrl->ctrl); >>> nvme_queue_async_events(&ctrl->ctrl); >>> } >>> @@ -791,8 +788,6 @@ static void nvme_rdma_reconnect_ctrl_work(struct >>> work_struct *work) >>> >>> return; >>> >>> -stop_admin_q: >>> - blk_mq_stop_hw_queues(ctrl->ctrl.admin_q); >>> requeue: >>> dev_info(ctrl->ctrl.device, "Failed reconnect attempt %d\n", >>> ctrl->ctrl.opts->nr_reconnects); >>> @@ -823,6 +818,13 @@ static void >>> nvme_rdma_error_recovery_work(struct work_struct *work) >>> blk_mq_tagset_busy_iter(&ctrl->admin_tag_set, >>> nvme_cancel_request, &ctrl->ctrl); >>> >>> + /* >>> + * queues are not a live anymore, so restart the queues to >>> fail fast >>> + * new IO >>> + */ >>> + blk_mq_start_stopped_hw_queues(ctrl->ctrl.admin_q, true); >>> + nvme_start_queues(&ctrl->ctrl); >>> + >>> nvme_rdma_reconnect_or_remove(ctrl); >>> } >>> >>> -- >>> >>> _______________________________________________ >>> Linux-nvme mailing list >>> Linux-nvme at lists.infradead.org >>> http://lists.infradead.org/mailman/listinfo/linux-nvme >> >