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_?. 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. -- Martin K. Petersen Oracle Linux Engineering
