nvme blk_update_request IO error observed on formatting device with kernels 5.5-rc1 and above.

* nvme blk_update_request IO error observed on formatting device with kernels 5.5-rc1 and above.
@ 2019-12-27 14:08 Dakshaja Uppalapati
  2019-12-27 15:03 ` Eduard Hasenleithner
  0 siblings, 1 reply; 6+ messages in thread
From: Dakshaja Uppalapati @ 2019-12-27 14:08 UTC (permalink / raw)
  To: linux-nvme, kbusch, eduard; +Cc: Potnuri Bharat Teja, Nirranjan Kirubaharan

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Hi,

I am trying to setup and run NVMF with tot linux kernel installed(5.5.0-rc3) on
both target and host. Attached is the target configuration using ramdisk device.

On host, I tried to format the LUN discovered from target machine by using
#mkfs.ext3 /dev/nvme0n1.

The following error is seen in dmesg:
[  219.507989] blk_update_request: I/O error, dev nvme0c0n1, sector 0 op 0x3:(DISCARD) flags 0x4000800 phys_seg 1 prio class 0

The above error is seen from kernel-5.5-rc1 onwards. Bisect points to the 
following commit:

530436c45ef2e446c12538a400e465929a0b3ade is the first bad commit 
commit 530436c45ef2e446c12538a400e465929a0b3ade
Author: Eduard Hasenleithner <eduard@hasenleithner.at>
Date:   Tue Nov 12 21:55:01 2019 +0100

    nvme: Discard workaround for non-conformant devices

    Users observe IOMMU related errors when performing discard on nvme from
    non-compliant nvme devices reading beyond the end of the DMA mapped
    ranges to discard.

    Two different variants of this behavior have been observed: SM22XX
    controllers round up the read size to a multiple of 512 bytes, and Phison
    E12 unconditionally reads the maximum discard size allowed by the spec
    (256 segments or 4kB).

    Make nvme_setup_discard unconditionally allocate the maximum DSM buffer
    so the driver DMA maps a memory range that will always succeed.

    Link: https://bugzilla.kernel.org/show_bug.cgi?id=202665 many
    Signed-off-by: Eduard Hasenleithner <eduard@hasenleithner.at>
    [changelog, use existing define, kernel coding style]
    Signed-off-by: Keith Busch <kbusch@kernel.org>

Please let me know if any info is needed further.

Thanks,
Dakshaja

[-- Attachment #2: nvmf.conf --]
[-- Type: application/octet-stream, Size: 1026 bytes --]

{
  "hosts": [],
  "ports": [
    {
      "addr": {
        "adrfam": "ipv4",
        "traddr": "",
        "treq": "not specified",
        "trsvcid": "4420",
        "trtype": "rdma"
      },
      "portid": 2,
      "referrals": [],
      "subsystems": []
    },
    {
      "addr": {
        "adrfam": "ipv4",
        "traddr": "10.0.2.1",
        "treq": "not specified",
        "trsvcid": "4420",
        "trtype": "rdma"
      },
      "portid": 1,
      "referrals": [],
      "subsystems": [
        "nvme-ram"
      ]
    }
  ],
  "subsystems": [
    {
      "allowed_hosts": [],
      "attr": {
        "allow_any_host": "1",
        "serial": "1850eae32a76fb",
        "version": "1.3"
      },
      "namespaces": [
        {
          "device": {
            "nguid": "00000000-0000-0000-0000-000000000000",
            "path": "/dev/ram0",
            "uuid": "af09ebe1-db1a-4eb6-97ef-bef00f42d59c"
          },
          "enable": 1,
          "nsid": 1
        }
      ],
      "nqn": "nvme-ram"
    }
  ]
}

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