Re: [PATCH v3 15/15] nvme: Ensure atomic writes will be executed atomically

[Christoph Hellwig]

On Thu, Jan 25, 2024 at 11:28:22AM +0000, John Garry wrote:
> We have limits checks in XFS iomap and fops.c, but we would also want to 
> ensure that the the block layer is not doing anything it shouldn't be doing 
> after submit_bio_noacct(), like merging atomic write BIOs which straddle a 
> boundary or exceed atomic_max (if there were any merging).
>
> The SCSI standard already has provision for error'ing an atomic write 
> command which exceeds the target atomic write capabilities, while NVMe 
> doesn't.

Can you get Oracle to propose this for NVMe?  It always helps if these
suggestions come from a large buyer of NVMe equipment.

> BTW, Christoph did mention that he would like to see this:
> https://lore.kernel.org/linux-nvme/20231109153603.GA2188@xxxxxx/

I can probably live with a sufficiently low-level block layer check.