nvme-multipath: fix hang when disk goes live over reconnect
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: - nvme_update_ns_ana_state() to call set_live only if ctrl is live - nvme_read_ana_log() call from nvme_mpath_init_identify() therefore only fetches and parses the ANA log; any erros in this process will fail the ctrl setup as appropriate; - a separate function nvme_mpath_update() is called in nvme_start_ctrl(); this parses the ANA log without fetching it. At this point the ctrl is live, therefore, disks can be set live normally. 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 <anton@lightbitslabs.com> Reviewed-by:
Sagi Grimberg <sagi@grimberg.me> Signed-off-by:
Christoph Hellwig <hch@lst.de>
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d6d67427