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:
0d0b660f214d ("nvme: add ANA support")
Signed-off-by: Anton Eidelman <anton@lightbitslabs.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>