Re: [PATCH 21/21] nvme: Support atomic writes

Christoph Hellwig
2023-11-09T15:46:27Z

On Thu, Nov 09, 2023 at 03:42:40PM +0000, Matthew Wilcox wrote:
> That wasn't the model we had in mind. In our thinking, it was fine to
> send a write that crossed the atomic write limit, but the drive wouldn't
> guarantee that it was atomic except at the atomic write boundary.
> Eg with an AWUN of 16kB, you could send five 16kB writes, combine them
> into a single 80kB write, and if the power failed midway through, the
> drive would guarantee that it had written 0, 16kB, 32kB, 48kB, 64kB or
> all 80kB. Not necessarily in order; it might have written bytes 16-32kB,
> 64-80kB and not the other three.

I can see some use for that, but I'm really worried that debugging
problems in the I/O merging and splitting will be absolute hell.