Re: [PATCH 08/14] scsi: sd: Optimal I/O size should be a multiple of reported granularity

Martin K. Petersen
2022-03-04T03:45:51Z

Bart,

> On 3/1/22 21:35, Martin K. Petersen wrote:
>> + if (min_xfer_bytes && opt_xfer_bytes & (min_xfer_bytes - 1)) {
>> + sd_first_printk(KERN_WARNING, sdkp,
>> + "Optimal transfer size %u bytes not a " \
>> + "multiple of preferred minimum block " \
>> + "size (%u bytes)\n",
>> + opt_xfer_bytes, min_xfer_bytes);
>> + return false;
>> + }
>
> Hmm ... what guarantees that min_xfer_bytes is a power of two? Did I
> perhaps overlook something?

Nothing in the spec, obviously, but I think we'd have a lot of headaches
further up the stack if that wasn't the case.

Do you know of any devices that report something unusual here?

--
Martin K. Petersen Oracle Linux Engineering