RE: [PATCH 1/3] scsi: storvsc: Fix max_outstanding_req_per_channel for Win8 and newer

[Dexuan Cui]

> From: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
> Sent: Thursday, December 17, 2020 12:33 PM
> 
> Current code overestimates the value of max_outstanding_req_per_channel
> for Win8 and newer hosts, since vmscsi_size_delta is set to the initial
> value of sizeof(vmscsi_win8_extension) rather than zero.  This may lead
> to wrong decisions when using ring_avail_percent_lowater equals to zero.
> The estimate of max_outstanding_req_per_channel is 'exact' for Win7 and
> older hosts.  A better choice, keeping the algorithm for the estimation
> simple, is to err the other way around, i.e., to underestimate for Win7
> and older but to use the exact value for Win8 and newer.
> 
> Suggested-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
> Cc: "James E.J. Bottomley" <jejb@xxxxxxxxxxxxx>
> Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
> Cc: linux-scsi@xxxxxxxxxxxxxxx

Reviewed-by: Dexuan Cui <decui@xxxxxxxxxxxxx>