On Thu, Mar 23, 2017 at 10:35:06AM -0400, James Bottomley wrote:

I'm certainly not saying we blindly follow t10, but I believe their
intent is to issue the next command from the completion of the first
(we can do this using qc->complete_fn, like atapi_request_sense).  That
way we don't get any tag problems because there's only one command
outstanding at once; reusing the qc means no allocation issues either.

The t10 approach does mean the SG_IO problem is actually fixable rather
than simply erroring out.

It would be sort of fixable, but with a lot of hackery.

That's up to you ... from the point of view of code documenting itself,
forming the ATA_16 TRIM in sd and not doing any satl transformation is
easier for others to follow, but if it's going to cause more code, I'm
only marginal on the advantages of easier to follow code.

I tried this earlier before giving up on it because it looked to ugly.
But I can complete that version of it and post it for people to compare.