Re: [PATCH v2 01/15] scsi: Add struct for args to execution functions

[Mike Christie <michael.christie@oracle.com>]

On 12/9/22 11:15 AM, Mike Christie wrote:
> On 12/9/22 4:40 AM, John Garry wrote:
>>>        * head injection*required*  here otherwise quiesce won't work
>>> @@ -249,13 +238,14 @@ int __scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
>>>       if (unlikely(scmd->resid_len > 0 && scmd->resid_len <= bufflen))
>>>           memset(buffer + bufflen - scmd->resid_len, 0, scmd->resid_len);
>>>   -    if (resid)
>>> -        *resid = scmd->resid_len;
>>> -    if (sense && scmd->sense_len)
>>> -        memcpy(sense, scmd->sense_buffer, SCSI_SENSE_BUFFERSIZE);
>>> -    if (sshdr)
>>> -        scsi_normalize_sense(scmd->sense_buffer, scmd->sense_len,
>>> -                     sshdr);
>>> +    if (args.resid)
>>> +        *args.resid = scmd->resid_len;
>>> +    if (args.sense && scmd->sense_len)
>>
>> I am not sure that you require the sense_len check as you effectively have that same check in scsi_execute_args(), which is the only caller which would have args.sense set. But I suppose __scsi_execute() is still a public API (so should still check); but, by that same token, we have no sanity check for args.sense_len value here then. Is it possible to make __scsi_execute() non-public or move/add the check for proper sense_len here? I'm being extra cautious about this, I suppose.
> Do people want the BUILD_BUG_ON we have now or a WARN/BUG?
> 
> If we move to a single check in __scsi_execute or some non-macro wrapper
> around it then we have to do a WARN/BUG. We do the macro approach now
> so we can do the BUILD_BUG_ON.

Maybe we have to switch to a WARN/BUG.

It looks like some compilers don't like:

const struct scsi_exec_args exec_args = {
	.sshdr = &sshdr,
};

scsi_execute_args(.... exec_args);

and will hit the:

#define scsi_execute_args(sdev, cmd, opf, buffer, bufflen, timeout,     \
                          retries, args)                                \
({                                                                      \
        BUILD_BUG_ON(args.sense &&                                      \
                     args.sense_len != SCSI_SENSE_BUFFERSIZE);          \

because the args's sense and sense_len are not cleared yet.