[Bug Report] PCIe errinject and hot-unplug causes nvme driver hang

[Sagi Grimberg]

On 21/04/2024 19:56, Nilay Shroff wrote:
>
> On 4/21/24 15:58, Sagi Grimberg wrote:
>>
>> On 18/04/2024 15:52, Nilay Shroff wrote:
>>> Hi,
>>>
>>> We found nvme driver hangs when disk IO is ongoing and if we inject pcie error and hot-unplug (not physical but logical unplug) the nvme disk.
>>>
>>> Notes and observations:
>>> ======================
>>> This is observed on the latest linus kernel tree (v6.9-rc4) however we believe this issue shall also be present on the older kernels.
>>>
>>> Test details:
>>> =============
>>> Steps to reproduce this issue:
>>>
>>> 1. Run some disk IO using fio or any other tool
>>> 2. While disk IO is running, inject pci error
>>> 3. disable the slot where nvme disk is attached (echo 0 > /sys/bus/pci/slots/<slot-no>/power)
>>>
>>> Kernel Logs:
>>> ============
>>> When we follow steps described in the test details we get the below logs:
>>>
>>> [  295.240811] nvme nvme1: controller is down; will reset: CSTS=0xffffffff, PCI_STATUS=0x10
>>> [  295.240837] nvme nvme1: Does your device have a faulty power saving mode enabled?
>>> [  295.240845] nvme nvme1: Try "nvme_core.default_ps_max_latency_us=0 pcie_aspm=off" and report a bug
>>> [  490.381591] INFO: task bash:2510 blocked for more than 122 seconds.
>>> [  490.381614]       Not tainted 6.9.0-rc4+ #8
>>> [  490.381618] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>>> [  490.381623] task:bash            state:D stack:0     pid:2510  tgid:2510  ppid:2509   flags:0x00042080
>>> [  490.381632] Call Trace:
>>> [  490.381635] [c00000006748f510] [c00000006748f550] 0xc00000006748f550 (unreliable)
>>> [  490.381644] [c00000006748f6c0] [c00000000001f3fc] __switch_to+0x13c/0x220
>>> [  490.381654] [c00000006748f720] [c000000000fb87e0] __schedule+0x268/0x7c4
>>> [  490.381663] [c00000006748f7f0] [c000000000fb8d7c] schedule+0x40/0x108
>>> [  490.381669] [c00000006748f860] [c000000000808bb4] blk_mq_freeze_queue_wait+0xa4/0xec
>>> [  490.381676] [c00000006748f8c0] [c00000000081eba8] del_gendisk+0x284/0x464
>>> [  490.381683] [c00000006748f920] [c0080000064c74a4] nvme_ns_remove+0x138/0x2ac [nvme_core]
>>> [  490.381697] [c00000006748f960] [c0080000064c7704] nvme_remove_namespaces+0xec/0x198 [nvme_core]
>>> [  490.381710] [c00000006748f9d0] [c008000006704b70] nvme_remove+0x80/0x168 [nvme]
>>> [  490.381752] [c00000006748fa10] [c00000000092a10c] pci_device_remove+0x6c/0x110
>>> [  490.381776] [c00000006748fa50] [c000000000a4f504] device_remove+0x70/0xc4
>>> [  490.381786] [c00000006748fa80] [c000000000a515d8] device_release_driver_internal+0x2a4/0x324
>>> [  490.381801] [c00000006748fad0] [c00000000091b528] pci_stop_bus_device+0xb8/0x104
>>> [  490.381817] [c00000006748fb10] [c00000000091b910] pci_stop_and_remove_bus_device+0x28/0x40
>>> [  490.381826] [c00000006748fb40] [c000000000072620] pci_hp_remove_devices+0x90/0x128
>>> [  490.381831] [c00000006748fbd0] [c008000004440504] disable_slot+0x40/0x90 [rpaphp]
>>> [  490.381839] [c00000006748fc00] [c000000000956090] power_write_file+0xf8/0x19c
>>> [  490.381846] [c00000006748fc80] [c00000000094b4f8] pci_slot_attr_store+0x40/0x5c
>>> [  490.381851] [c00000006748fca0] [c0000000006e5dc4] sysfs_kf_write+0x64/0x78
>>> [  490.381858] [c00000006748fcc0] [c0000000006e48d8] kernfs_fop_write_iter+0x1b0/0x290
>>> [  490.381864] [c00000006748fd10] [c0000000005e0f4c] vfs_write+0x3b0/0x4f8
>>> [  490.381871] [c00000006748fdc0] [c0000000005e13c0] ksys_write+0x84/0x140
>>> [  490.381876] [c00000006748fe10] [c000000000030a84] system_call_exception+0x124/0x330
>>> [  490.381882] [c00000006748fe50] [c00000000000cedc] system_call_vectored_common+0x15c/0x2ec
>>>
>>> NVMe controller state:
>>> ======================
>>> # cat /sys/class/nvme/nvme1/state
>>> deleting (no IO)
>>>
>>> Process State:
>>> ==============
>>> # ps -aex
>>>      [..]
>>>      2510 pts/2    Ds+    0:00 -bash USER=root LOGNAME=root HOME=/root PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin SHELL=/bin/bash TERM=xterm-256colo
>>>      2549 ?        Ds     0:14 fio --filename=/dev/nvme1n1 --direct=1 --rw=randrw --bs=4k --ioengine=psync --iodepth=256 --runtime=300 --numjobs=1 --time_based
>>>      [..]
>>>
>>> Observation:
>>> ============
>>> As it's apparent from the above logs that "disable-slot" (pid 2510) is waiting (uninterruptible-sleep)
>>> for queue to be freezed because the in-flight IO(s) couldn't finish. Moreover the IO(s) which were
>>> in-flight actually times-out however nvme_timeout() doesn't cancel those IOs but logs this error
>>> "Try "nvme_core.default_ps_max_latency_us=0 pcie_aspm=off" and report a bug" and returns BLK_EH_DONE.
>>> As those in-fligh IOs were not cancelled, the NVMe driver code which runs in the context of
>>> "disable-slot" couldn't forward progress and NVMe controller state remains in "deleting (no IO)"
>>> indefinitely. The only way we found to come out of this state is to reboot the system.
>>>
>>> Proposed fix:
>>> ============
>>> static void nvme_remove(struct pci_dev *pdev)
>>> {
>>>      struct nvme_dev *dev = pci_get_drvdata(pdev);
>>>
>>>      nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_DELETING);
>>>      pci_set_drvdata(pdev, NULL);
>>>
>>>      if (!pci_device_is_present(pdev)) {
>>>          nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_DEAD);
>>>          nvme_dev_disable(dev, true);
>>>      }
>>>      flush_work(&dev->ctrl.reset_work);
>>>      nvme_stop_ctrl(&dev->ctrl);
>>>      nvme_remove_namespaces(&dev->ctrl); <== here cntrl state is set to "deleting (no IO)"
>>>           [..]
>>> }
>>>
>>> As shown above, nvme_remove() invokes nvme_dev_disable(), however, it is only invoked if the
>>> device is physically removed. As nvme_dev_disable() helps cancel pending IOs, does it makes
>>> sense to unconditionally cancel pending IOs before moving on? Or are there any side effect if
>>> we were to unconditionally invoke nvme_dev_disable() at the first place?
>> Shouldn't the correct place to handle the cancellation is nvme_error_detected() given that the
>> pci error is preventing the request from completing and the timeout handler from addressing it?
>>
> If a platform supports pci-error-recovery then it may be possible to cancel pending IOs from
> nvme_error_detected(), however, if the platform doesn't support pci error recovery then
> nvme_error_detected() would never be called. In fact, the issue which I reported above was
> discovered on a platform which has pci-error-recovery disabled.
>
> I also tested this scenario on a platform supporting the pci error recovery. On this platform,
> when I ran this test (PCI error injection followed by NVMe hot unpulg), I found that the
> pci-error-recovery thread races with hot-unplug task, please find below the dmesg logs
> collected when this issue manifests:
>
> INFO: task eehd:187 blocked for more than 122 seconds.
>        Not tainted 6.9.0-rc4+ #8
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:eehd            state:D stack:0     pid:187   tgid:187   ppid:2      flags:0x00000000
> Call Trace:
> [c0000000089bf890] [c000000000fb027c] vsnprintf+0x3f8/0x578 (unreliable)
> [c0000000089bfa40] [c00000000001f3fc] __switch_to+0x13c/0x220
> [c0000000089bfaa0] [c000000000fb87e0] __schedule+0x268/0x7c4
> [c0000000089bfb70] [c000000000fb8d7c] schedule+0x40/0x108
> [c0000000089bfbe0] [c000000000fb93f8] schedule_preempt_disabled+0x20/0x30
> [c0000000089bfc00] [c000000000fbbe84] __mutex_lock.constprop.0+0x5f4/0xc54
> [c0000000089bfca0] [c000000000916380] pci_lock_rescan_remove+0x28/0x3c
> [c0000000089bfcc0] [c00000000004fa4c] eeh_pe_report_edev+0x3c/0x52c
> [c0000000089bfda0] [c00000000004ffdc] eeh_pe_report+0xa0/0x158
> [c0000000089bfe40] [c000000000050490] eeh_handle_normal_event+0x310/0xa24
> [c0000000089bff30] [c000000000051078] eeh_event_handler+0x118/0x19c
> [c0000000089bff90] [c00000000018d29c] kthread+0x138/0x140
> [c0000000089bffe0] [c00000000000dd58] start_kernel_thread+0x14/0x18
>
> INFO: task bash:5420 blocked for more than 122 seconds.
>        Not tainted 6.9.0-rc4+ #8
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:bash            state:D stack:0     pid:5420  tgid:5420  ppid:5419   flags:0x00042080
> Call Trace:
> [c000000054c67510] [c000000054c67550] 0xc000000054c67550 (unreliable)
> [c000000054c676c0] [c00000000001f3fc] __switch_to+0x13c/0x220
> [c000000054c67720] [c000000000fb87e0] __schedule+0x268/0x7c4
> [c000000054c677f0] [c000000000fb8d7c] schedule+0x40/0x108
> [c000000054c67860] [c000000000808bb4] blk_mq_freeze_queue_wait+0xa4/0xec
> [c000000054c678c0] [c00000000081eba8] del_gendisk+0x284/0x464
> [c000000054c67920] [c00800000b7174a4] nvme_ns_remove+0x138/0x2ac [nvme_core]
> [c000000054c67960] [c00800000b717704] nvme_remove_namespaces+0xec/0x198 [nvme_core]
> [c000000054c679d0] [c008000006294b70] nvme_remove+0x80/0x168 [nvme]
> [c000000054c67a10] [c00000000092a10c] pci_device_remove+0x6c/0x110
> [c000000054c67a50] [c000000000a4f504] device_remove+0x70/0xc4
> [c000000054c67a80] [c000000000a515d8] device_release_driver_internal+0x2a4/0x324
> [c000000054c67ad0] [c00000000091b528] pci_stop_bus_device+0xb8/0x104
> [c000000054c67b10] [c00000000091b910] pci_stop_and_remove_bus_device+0x28/0x40
> [c000000054c67b40] [c000000000072620] pci_hp_remove_devices+0x90/0x128
> [c000000054c67bd0] [c008000004380504] disable_slot+0x40/0x90 [rpaphp]
> [c000000054c67c00] [c000000000956090] power_write_file+0xf8/0x19c
> [c000000054c67c80] [c00000000094b4f8] pci_slot_attr_store+0x40/0x5c
> [c000000054c67ca0] [c0000000006e5dc4] sysfs_kf_write+0x64/0x78
> [c000000054c67cc0] [c0000000006e48d8] kernfs_fop_write_iter+0x1b0/0x290
> [c000000054c67d10] [c0000000005e0f4c] vfs_write+0x3b0/0x4f8
> [c000000054c67dc0] [c0000000005e13c0] ksys_write+0x84/0x140
> [c000000054c67e10] [c000000000030a84] system_call_exception+0x124/0x330
> [c000000054c67e50] [c00000000000cedc] system_call_vectored_common+0x15c/0x2ec
>
>
> As we can see above the task eehd:187 (pci-error-recovery thread) is blocked for
> acquiring the mutex (pci_rescan_remove_lock). The hot-unplug task (bash: 5420)
> is blocked on the request queue to be freezed. The hot-unplug task first acquires
> the pci_rescan_remove_lock and then invokes nvme_remove() method. So in summary,
> in the traces shown above, as hot-unplug task is unable to proceed, it has also
> blocked the pci-error-recovery thread.

Yea that needs fixing.

>
> On another note, if pci-error-recovery thread could progress first acquiring
> pci_rescan_remove_lock then it shall be able to recover the pci error and hence
> pending IOs could be finished. Later when hot-unplug task starts, it could
> forward progress and cleanup all resources used by the nvme disk.
>
> So does it make sense if we unconditionally cancel the pending IOs from
> nvme_remove() before it forward progress to remove namespaces?

The driver attempts to allow inflights I/O to complete successfully, if 
the device
is still present in the remove stage. I am not sure we want to 
unconditionally fail these
I/Os.    Keith?