RE: [Regression] fstrim hangs on Hyper-V: caused by "block: improve handling of the magic discard payload"

[Dexuan Cui]

> From: Christoph Hellwig [mailto:hch@xxxxxx]
> Sent: Thursday, January 12, 2017 23:53
> To: Dexuan Cui <decui@xxxxxxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>; linux-block@xxxxxxxxxxxxxxx; Jens Axboe
> <axboe@xxxxxx>; Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>; linux-
> kernel@xxxxxxxxxxxxxxx; KY Srinivasan <kys@xxxxxxxxxxxxx>; Chris Valean
> (Cloudbase Solutions SRL) <v-chvale@xxxxxxxxxxxxx>
> Subject: Re: [Regression] fstrim hangs on Hyper-V: caused by "block: improve
> handling of the magic discard payload"
> 
> Can you check if this debug printk triggers for the discard commands?
> 
> ---
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 888e16e..7ab7d08 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1031,6 +1031,10 @@ static void storvsc_command_completion(struct
> storvsc_cmd_request *cmd_request,
>  			data_transfer_length = 0;
>  	}
> 
> +	if (cmd_request->payload->range.len != data_transfer_length)
> +		printk_ratelimited("request len: %u, transfer len: %u\n",
> +			cmd_request->payload->range.len,
> +			data_transfer_length);
>  	scsi_set_resid(scmnd,
>  		cmd_request->payload->range.len - data_transfer_length);
> 

// I fixed the small building issue (data_transfer_length  ==>  vm_srb->data_transfer_length).

No, the printk doesn't trigger for fstrim.

It does trigger at the early boot phase, though.

# dmesg |grep len:
[    0.000000] log_buf_len: 134217728 bytes
[    7.073423] request len: 255, transfer len: 12
[    7.084937] request len: 255, transfer len: 52
[    7.121728] request len: 64, transfer len: 12
[    7.121915] request len: 64, transfer len: 12
[    7.123180] request len: 64, transfer len: 12
[    7.123367] request len: 64, transfer len: 12
[    7.127193] request len: 64, transfer len: 12
[    7.127350] request len: 64, transfer len: 12
[    7.178930] request len: 255, transfer len: 12
[    7.179045] request len: 255, transfer len: 52

-- Dexuan