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Sun, 27 Oct 2024 17:02:21 +0000 (GMT) From: Nilay Shroff To: linux-nvme@lists.infradead.org Cc: kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, axboe@fb.com, chaitanyak@nvidia.com, dlemoal@kernel.org, gjoyce@linux.ibm.com, Nilay Shroff Subject: [PATCH 0/3] nvme: fix system fault observed while shutting down controller Date: Sun, 27 Oct 2024 22:32:03 +0530 Message-ID: <20241027170209.440776-1-nilay@linux.ibm.com> X-Mailer: git-send-email 2.45.2 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: WUIF54psXobKG9FgbL-hX3Pbfz5JNs1T X-Proofpoint-GUID: WUIF54psXobKG9FgbL-hX3Pbfz5JNs1T Content-Transfer-Encoding: 8bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 impostorscore=0 lowpriorityscore=0 suspectscore=0 mlxlogscore=804 mlxscore=0 phishscore=0 bulkscore=0 priorityscore=1501 adultscore=0 clxscore=1015 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2410270148 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241027_100252_597534_491262DA X-CRM114-Status: GOOD ( 19.14 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org Hi, This patch series addresses the system fault observed while shutting down fabric controller. We already fixed it[1] earlier however it was later relaized that we do have a better and optimal way to address it [2]. The first patch in the series reverts the changes implemented in [3] and [4]. So essentially we're making keep-alive operation asynchronous again as it was earlier. The second patch in the series fix the kernel crash observed while shutting down fabric controller. The third patch in the series uses the nvme_ctrl_state function for retrieving the controller state. The system fault was observed due to the keep-alive request sneaking in while shutting down fabric controller. We encounter the below intermittent kernel crash while running blktest nvme/037: dmesg output: ------------ run blktests nvme/037 at 2024-10-04 03:59:27 nvme nvme1: new ctrl: "blktests-subsystem-5" nvme nvme1: Failed to configure AEN (cfg 300) nvme nvme1: Removing ctrl: NQN "blktests-subsystem-5" nvme nvme1: long keepalive RTT (54760 ms) nvme nvme1: failed nvme_keep_alive_end_io error=4 BUG: Kernel NULL pointer dereference on read at 0x00000080 Faulting instruction address: 0xc00000000091c9f8 Oops: Kernel access of bad area, sig: 7 [#1] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries CPU: 28 UID: 0 PID: 338 Comm: kworker/u263:2 Kdump: loaded Not tainted 6.11.0+ #89 Hardware name: IBM,9043-MRX POWER10 (architected) 0x800200 0xf000006 of:IBM,FW1060.00 (NM1060_028) hv:phyp pSeries Workqueue: nvme-wq nvme_keep_alive_work [nvme_core] NIP: c00000000091c9f8 LR: c00000000084150c CTR: 0000000000000004 NIP [c00000000091c9f8] sbitmap_any_bit_set+0x68/0xb8 LR [c00000000084150c] blk_mq_do_dispatch_ctx+0xcc/0x280 Call Trace: autoremove_wake_function+0x0/0xbc (unreliable) __blk_mq_sched_dispatch_requests+0x114/0x24c blk_mq_sched_dispatch_requests+0x44/0x84 blk_mq_run_hw_queue+0x140/0x220 nvme_keep_alive_work+0xc8/0x19c [nvme_core] process_one_work+0x200/0x4e0 worker_thread+0x340/0x504 kthread+0x138/0x140 start_kernel_thread+0x14/0x18 We realized that the above crash is regression caused due to changes implemented in commit a54a93d0e359 ("nvme: move stopping keep-alive into nvme_uninit_ctrl()"). Ideally we should stop keep-alive at the very beggining of the controller shutdown code path so that it wouldn't sneak in or interfere with the shutdown operation. However we removed the keep alive stop operation from the beginning of the controller shutdown code path in commit a54a93d0e359 ("nvme: move stopping keep-alive into nvme_ uninit_ctrl()") and that now created the possibility of keep-alive sneaking in and interfering with the shutdown operation and causing observed kernel crash. So to fix this crash, now we're adding back the keep-alive stop operation at very beginning of the fabric controller shutdown code path so that the actual controller shutdown opeation only begins after it's ensured that keep-alive operation is not in-flight and also it can't be scheduled in future. This fixed in the second patch of the series. The third patch in the series addresses the use of ctrl->lock before accessing NVMe controller state in nvme_keep_alive_end_io function. With introduction of helper nvme_ctrl_state, we no longer need to first acquire ctrl->lock before accessing the NVMe controller state. So this patch removes the use of ctrl->lock from nvme_keep_alive_end_io function and replaces it with helper nvme_ctrl_state call. [1]https://lore.kernel.org/all/ZxFSkNI2p65ucTB5@kbusch-mbp.dhcp.thefacebook.com/ [2]https://lore.kernel.org/all/196f4013-3bbf-43ff-98b4-9cb2a96c20c2@grimberg.me/ [3]https://lore.kernel.org/all/20241016030339.54029-3-nilay@linux.ibm.com/ [4]https://lore.kernel.org/all/20241016030339.54029-4-nilay@linux.ibm.com/ Nilay Shroff (3): Revert "nvme: make keep-alive synchronous operation" nvme-fabrics: fix kernel crash while shutting down controller nvme: use helper nvme_ctrl_state in nvme_keep_alive_end_io function drivers/nvme/host/core.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) -- 2.45.2