Re: [PATCH 01/21] block: Add atomic write operations to request_queue limits

Christoph Hellwig
2023-11-10T06:23:32Z

On Thu, Nov 09, 2023 at 05:01:10PM +0000, John Garry wrote:
> Generally they come from the same device property. Then since
> atomic_write_unit_max_bytes must be a power-of-2 (and
> atomic_write_max_bytes may not be), they may be different.

How much do we care about supporting the additional slack over the
power of two version?

> In addition,
> atomic_write_unit_max_bytes is required to be limited by whatever is
> guaranteed to be able to fit in a bio.

The limit what fits into a bio is UINT_MAX, not sure that matters :)

> atomic_write_max_bytes is really only relevant for merging writes. Maybe we
> should not even expose via sysfs.

Or we need to have a good separate discussion on even supporting any
merges. Willy chimed in that supporting merges was intentional,
but I'd really like to see numbers justifying it.