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[62.219.42.90]) by smtp.gmail.com with ESMTPSA id j7sm15252078wrr.27.2021.09.19.03.19.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 19 Sep 2021 03:19:41 -0700 (PDT) Subject: Re: [PATCH] nvme/mpath: fix hang when disk goes live over reconnect To: Anton Eidelman , linux-nvme@lists.infradead.org, hch@lst.de, kbusch@kernel.org, axboe@fb.com Cc: Anton Eidelman References: <20210918215729.388968-1-anton@lightbitslabs.com> From: Sagi Grimberg Message-ID: Date: Sun, 19 Sep 2021 13:19:39 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210918215729.388968-1-anton@lightbitslabs.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210919_031942_961915_82C1EB60 X-CRM114-Status: GOOD ( 29.16 ) 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: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 9/19/21 12:57 AM, Anton Eidelman wrote: > nvme_mpath_init_identify() invoked from nvme_init_identify() > fetches a fresh ANA log from the ctrl. > This is essential to have an up to date path states > for both existing namespaces and for those scan_work > may discover once the ctrl is up. > > This happens in the following cases: > 1) A new ctrl is being connected. > 2) An existing ctrl is successfully reconnected. > 3) An existing ctrl is being reset. > > While in (1) ctrl->namespaces is empty, (2 & 3) may have namespaces, > and nvme_read_ana_log() may call nvme_update_ns_ana_state(). > > This result in a hang when the ANA state of an existing namespace > changes and makes the disk live: nvme_mpath_set_live() issues > IO to the namespace through the ctrl, which does NOT have IO queues yet. > See sample hang below. > > Solution: > - move nvme_read_ana_log() call from nvme_mpath_init_identify() > into a separate function, nvme_mpath_update(). > - call this function in nvme_start_ctrl() - here the ctrl is ready. > > Downside: in case nvme_read_ana_log() fails, we do not find this out > in nvme_mpath_init_identify(). > > Alernative solution: > nvme_get_log() in nvme_mpath_init_identify(), but don't parse. > Then nvme_start_ctrl() can just queue_work(nvme_wq, &ctrl->ana_work), > along with scan_work. > The ctrl->ana_log_buf contents is valid for scan_work, > and ana_work will re-fetch and parse it. > Downside: fetching an ANA log from the ctrl twice. > > Sample failure: > nvme nvme0: starting error recovery > nvme nvme0: Reconnecting in 10 seconds... > block nvme0n6: no usable path - requeuing I/O > INFO: task kworker/u8:3:312 blocked for more than 122 seconds. > Tainted: G E 5.14.5-1.el7.elrepo.x86_64 #1 > Workqueue: nvme-wq nvme_tcp_reconnect_ctrl_work [nvme_tcp] > Call Trace: > __schedule+0x2a2/0x7e0 > schedule+0x4e/0xb0 > io_schedule+0x16/0x40 > wait_on_page_bit_common+0x15c/0x3e0 > do_read_cache_page+0x1e0/0x410 > read_cache_page+0x12/0x20 > read_part_sector+0x46/0x100 > read_lba+0x121/0x240 > efi_partition+0x1d2/0x6a0 > bdev_disk_changed.part.0+0x1df/0x430 > bdev_disk_changed+0x18/0x20 > blkdev_get_whole+0x77/0xe0 > blkdev_get_by_dev+0xd2/0x3a0 > __device_add_disk+0x1ed/0x310 > device_add_disk+0x13/0x20 > nvme_mpath_set_live+0x138/0x1b0 [nvme_core] > nvme_update_ns_ana_state+0x2b/0x30 [nvme_core] > nvme_update_ana_state+0xca/0xe0 [nvme_core] > nvme_parse_ana_log+0xac/0x170 [nvme_core] > nvme_read_ana_log+0x7d/0xe0 [nvme_core] > nvme_mpath_init_identify+0x105/0x150 [nvme_core] > nvme_init_identify+0x2df/0x4d0 [nvme_core] > nvme_init_ctrl_finish+0x8d/0x3b0 [nvme_core] > nvme_tcp_setup_ctrl+0x337/0x390 [nvme_tcp] > nvme_tcp_reconnect_ctrl_work+0x24/0x40 [nvme_tcp] > process_one_work+0x1bd/0x360 > worker_thread+0x50/0x3d0 > > Signed-off-by: Anton Eidelman > --- > drivers/nvme/host/core.c | 1 + > drivers/nvme/host/multipath.c | 9 ++++++--- > drivers/nvme/host/nvme.h | 4 ++++ > 3 files changed, 11 insertions(+), 3 deletions(-) > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > index 97f8211cf92c..884ca1f6f80b 100644 > --- a/drivers/nvme/host/core.c > +++ b/drivers/nvme/host/core.c > @@ -4325,6 +4325,7 @@ void nvme_start_ctrl(struct nvme_ctrl *ctrl) > nvme_enable_aen(ctrl); > > if (ctrl->queue_count > 1) { > + nvme_mpath_update(ctrl); Does this ordering now becomes subtle as it needs to run before we queue the ns scan? > nvme_queue_scan(ctrl); > nvme_start_queues(ctrl); > } _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme