[PATCH RFC] nvmet: fix tmpfs-based backstores support

[Chaitanya Kulkarni]

On 11/18/2021 12:29 AM, Maurizio Lombardi wrote:
> External email: Use caution opening links or attachments
> 
> 
> On Thu, Nov 18, 2021 at 01:59:29AM +0000, Chaitanya Kulkarni wrote:
>> We will need blktests for this.
>>
>> Also, can you share performance numbers with this patch and
>> the errors that you are getting without this patch ?
> 
> Ok, I will try to run blktests and provide some performance numbers.
> 
> Without this patch, writes get lost:
> 
> [root at kvm-02-guest03 ~]# nvme connect -t tcp -a 10.37.153.75 -n test-nqn -s 4080
> [root at kvm-02-guest03 ~]# dd if=/dev/urandom of=/dev/nvme0n1 bs=1M count=1
> 1+0 records in
> 1+0 records out
> 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0604551 s, 17.3 MB/s
> [root at kvm-02-guest03 ~]# hexdump -C /dev/nvme0n1
> 00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> *
> 06400000
> 
> dmesg output:
> 
> [81489.687548] blk_update_request: critical target error, dev nvme0c0n1, sector 0 op 0x1:(WRITE) flags 0x2000800 phys_seg 256 prio class 0
> [81489.691139] buffer_io_error: 246 callbacks suppressed
> [81489.691141] Buffer I/O error on dev nvme0n1, logical block 0, lost async page write
> [81489.695013] Buffer I/O error on dev nvme0n1, logical block 1, lost async page write
> [81489.697183] Buffer I/O error on dev nvme0n1, logical block 2, lost async page write
> [81489.699239] Buffer I/O error on dev nvme0n1, logical block 3, lost async page write
> [81489.701297] Buffer I/O error on dev nvme0n1, logical block 4, lost async page write
> [81489.703374] Buffer I/O error on dev nvme0n1, logical block 5, lost async page write
> [81489.705459] Buffer I/O error on dev nvme0n1, logical block 6, lost async page write
> [81489.707511] Buffer I/O error on dev nvme0n1, logical block 7, lost async page write
> [81489.709438] Buffer I/O error on dev nvme0n1, logical block 8, lost async page write
> [81489.711364] Buffer I/O error on dev nvme0n1, logical block 9, lost async page write
> 
> Maurizio
> 

Thanks for the prompt reply and sharing this ..

Please send a formal-patch (non-RFC) with the testing done.