On 21.01.2020 09:14, Martin K. Petersen wrote: > > Kirill, > >> + if (flags & BLKDEV_ZERO_NOUNMAP) >> + req_flags |= REQ_NOUNMAP; >> + if (flags & BLKDEV_ZERO_ALLOCATE) >> + req_flags |= REQ_NOZERO|REQ_NOUNMAP; > > I find there is some dissonance between using BLKDEV_ZERO_ALLOCATE to > describe this operation in one case and REQ_NOZERO in the other. > > I understand why not zeroing is important in your case. However, I think > the allocation aspect is semantically more important. Also, in the case > of SCSI, the allocated blocks will typically appear zeroed. So from that > perspective REQ_NOZERO doesn't really make sense. I would really prefer > to use REQ_ALLOCATE to describe this operation. I agree that "do not > write every block" is important too. I just don't have a good suggestion > for how to express that as an additional qualifier to REQ_ALLOCATE_?. No problem, I'll rename the modifier. > Also, adding to the confusion: In the context of SCSI, ANCHOR requires > UNMAP. So my head hurts a bit when I read REQ_NOZERO|REQ_NOUNMAP and > have to translate that into ANCHOR|UNMAP. > > Longer term, I think we should consider introducing REQ_OP_SINGLE_RANGE > or something like that as an umbrella operation that can be used to > describe zeroing, allocating, and other things that operate on a single > LBA range with no payload. Thus removing both the writiness and the > zeroness from the existing REQ_OP_WRITE_ZEROES conduit. > > Naming issues aside, your patch looks fine. I'll try to rebase my SCSI > patches on top of your series to see how things fit. Ok, thanks.
