ecca390e80
A deadlock happens in the following scenario with multipath:
1) scan_work(nvme0) detects a new nsid while nvme0
is an optimized path to it, path nvme1 happens to be
inaccessible.
2) Before scan_work is complete nvme0 disconnect is initiated
nvme_delete_ctrl_sync() sets nvme0 state to NVME_CTRL_DELETING
3) scan_work(1) attempts to submit IO,
but nvme_path_is_optimized() observes nvme0 is not LIVE.
Since nvme1 is a possible path IO is requeued and scan_work hangs.
--
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_set_ns_ana_state+0x1e/0x30 [nvme_core]
kernel: nvme_parse_ana_log+0xa1/0x180 [nvme_core]
kernel: nvme_mpath_add_disk+0x47/0x90 [nvme_core]
kernel: nvme_validate_ns+0x396/0x940 [nvme_core]
kernel: nvme_scan_work+0x24f/0x380 [nvme_core]
kernel: process_one_work+0x1db/0x380
kernel: worker_thread+0x249/0x400
kernel: kthread+0x104/0x140
--
4) Delete also hangs in flush_work(ctrl->scan_work)
from nvme_remove_namespaces().
Similiarly a deadlock with ana_work may happen: if ana_work has started
and calls nvme_mpath_set_live and device_add_disk, it will
trigger I/O. When we trigger disconnect I/O will block because
our accessible (optimized) path is disconnecting, but the alternate
path is inaccessible, so I/O blocks. Then disconnect tries to flush
the ana_work and hangs.
[ 605.550896] Workqueue: nvme-wq nvme_ana_work [nvme_core]
[ 605.552087] Call Trace:
[ 605.552683] __schedule+0x2b9/0x6c0
[ 605.553507] schedule+0x42/0xb0
[ 605.554201] io_schedule+0x16/0x40
[ 605.555012] do_read_cache_page+0x438/0x830
[ 605.556925] read_cache_page+0x12/0x20
[ 605.557757] read_dev_sector+0x27/0xc0
[ 605.558587] amiga_partition+0x4d/0x4c5
[ 605.561278] check_partition+0x154/0x244
[ 605.562138] rescan_partitions+0xae/0x280
[ 605.563076] __blkdev_get+0x40f/0x560
[ 605.563830] blkdev_get+0x3d/0x140
[ 605.564500] __device_add_disk+0x388/0x480
[ 605.565316] device_add_disk+0x13/0x20
[ 605.566070] nvme_mpath_set_live+0x5e/0x130 [nvme_core]
[ 605.567114] nvme_update_ns_ana_state+0x2c/0x30 [nvme_core]
[ 605.568197] nvme_update_ana_state+0xca/0xe0 [nvme_core]
[ 605.569360] nvme_parse_ana_log+0xa1/0x180 [nvme_core]
[ 605.571385] nvme_read_ana_log+0x76/0x100 [nvme_core]
[ 605.572376] nvme_ana_work+0x15/0x20 [nvme_core]
[ 605.573330] process_one_work+0x1db/0x380
[ 605.574144] worker_thread+0x4d/0x400
[ 605.574896] kthread+0x104/0x140
[ 605.577205] ret_from_fork+0x35/0x40
[ 605.577955] INFO: task nvme:14044 blocked for more than 120 seconds.
[ 605.579239] Tainted: G OE 5.3.5-050305-generic #201910071830
[ 605.580712] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 605.582320] nvme D 0 14044 14043 0x00000000
[ 605.583424] Call Trace:
[ 605.583935] __schedule+0x2b9/0x6c0
[ 605.584625] schedule+0x42/0xb0
[ 605.585290] schedule_timeout+0x203/0x2f0
[ 605.588493] wait_for_completion+0xb1/0x120
[ 605.590066] __flush_work+0x123/0x1d0
[ 605.591758] __cancel_work_timer+0x10e/0x190
[ 605.593542] cancel_work_sync+0x10/0x20
[ 605.594347] nvme_mpath_stop+0x2f/0x40 [nvme_core]
[ 605.595328] nvme_stop_ctrl+0x12/0x50 [nvme_core]
[ 605.596262] nvme_do_delete_ctrl+0x3f/0x90 [nvme_core]
[ 605.597333] nvme_sysfs_delete+0x5c/0x70 [nvme_core]
[ 605.598320] dev_attr_store+0x17/0x30
Fix this by introducing a new state: NVME_CTRL_DELETE_NOIO, which will
indicate the phase of controller deletion where I/O cannot be allowed
to access the namespace. NVME_CTRL_DELETING still allows mpath I/O to
be issued to the bottom device, and only after we flush the ana_work
and scan_work (after nvme_stop_ctrl and nvme_prep_remove_namespaces)
we change the state to NVME_CTRL_DELETING_NOIO. Also we prevent ana_work
from re-firing by aborting early if we are not LIVE, so we should be safe
here.
In addition, change the transport drivers to follow the updated state
machine.
Fixes: 0d0b660f214d ("nvme: add ANA support")
Reported-by: Anton Eidelman <anton@lightbitslabs.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Linux kernel
============
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