• Anton Eidelman's avatar
    nvme-multipath: fix deadlock due to head->lock · d8a22f85
    Anton Eidelman authored
    In the following scenario scan_work and ana_work will deadlock:
    
    When scan_work calls nvme_mpath_add_disk() this holds ana_lock
    and invokes nvme_parse_ana_log(), which may issue IO
    in device_add_disk() and hang waiting for an accessible path.
    
    While nvme_mpath_set_live() only called when nvme_state_is_live(),
    a transition may cause NVME_SC_ANA_TRANSITION and requeue the IO.
    
    Since nvme_mpath_set_live() holds ns->head->lock, an ana_work on
    ANY ctrl will not be able to complete nvme_mpath_set_live()
    on the same ns->head, which is required in order to update
    the new accessible path and remove NVME_NS_ANA_PENDING..
    Therefore IO never completes: deadlock [1].
    
    Fix:
    Move device_add_disk out of the head->lock and protect it with an
    atomic test_and_set for a new NVME_NS_HEAD_HAS_DISK bit.
    
    [1]:
    kernel: INFO: task kworker/u8:2:160 blocked for more than 120 seconds.
    kernel:       Tainted: G           OE     5.3.5-050305-generic #201910071830
    kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
    kernel: kworker/u8:2    D    0   160      2 0x80004000
    kernel: Workqueue: nvme-wq nvme_ana_work [nvme_core]
    kernel: Call Trace:
    kernel:  __schedule+0x2b9/0x6c0
    kernel:  schedule+0x42/0xb0
    kernel:  schedule_preempt_disabled+0xe/0x10
    kernel:  __mutex_lock.isra.0+0x182/0x4f0
    kernel:  __mutex_lock_slowpath+0x13/0x20
    kernel:  mutex_lock+0x2e/0x40
    kernel:  nvme_update_ns_ana_state+0x22/0x60 [nvme_core]
    kernel:  nvme_update_ana_state+0xca/0xe0 [nvme_core]
    kernel:  nvme_parse_ana_log+0xa1/0x180 [nvme_core]
    kernel:  nvme_read_ana_log+0x76/0x100 [nvme_core]
    kernel:  nvme_ana_work+0x15/0x20 [nvme_core]
    kernel:  process_one_work+0x1db/0x380
    kernel:  worker_thread+0x4d/0x400
    kernel:  kthread+0x104/0x140
    kernel:  ret_from_fork+0x35/0x40
    kernel: INFO: task kworker/u8:4:439 blocked for more than 120 seconds.
    kernel:       Tainted: G           OE     5.3.5-050305-generic #201910071830
    kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
    kernel: kworker/u8:4    D    0   439      2 0x80004000
    kernel: Workqueue: nvme-wq nvme_scan_work [nvme_core]
    kernel: Call Trace:
    kernel:  __schedule+0x2b9/0x6c0
    kernel:  schedule+0x42/0xb0
    kernel:  io_schedule+0x16/0x40
    kernel:  do_read_cache_page+0x438/0x830
    kernel:  read_cache_page+0x12/0x20
    kernel:  read_dev_sector+0x27/0xc0
    kernel:  read_lba+0xc1/0x220
    kernel:  efi_partition+0x1e6/0x708
    kernel:  check_partition+0x154/0x244
    kernel:  rescan_partitions+0xae/0x280
    kernel:  __blkdev_get+0x40f/0x560
    kernel:  blkdev_get+0x3d/0x140
    kernel:  __device_add_disk+0x388/0x480
    kernel:  device_add_disk+0x13/0x20
    kernel:  nvme_mpath_set_live+0x119/0x140 [nvme_core]
    kernel:  nvme_update_ns_ana_state+0x5c/0x60 [nvme_core]
    kernel:  nvme_mpath_add_disk+0xbe/0x100 [nvme_core]
    kernel:  nvme_validate_ns+0x396/0x940 [nvme_core]
    kernel:  nvme_scan_work+0x256/0x390 [nvme_core]
    kernel:  process_one_work+0x1db/0x380
    kernel:  worker_thread+0x4d/0x400
    kernel:  kthread+0x104/0x140
    kernel:  ret_from_fork+0x35/0x40
    
    Fixes: 0d0b660f ("nvme: add ANA support")
    Signed-off-by: default avatarAnton Eidelman <anton@lightbitslabs.com>
    Signed-off-by: default avatarSagi Grimberg <sagi@grimberg.me>
    Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
    d8a22f85
multipath.c 18.9 KB