[PATCH 02/12] block: take io_opt and io_min into account for max_sectors

[Bart Van Assche]

On 5/28/24 22:04, Christoph Hellwig wrote:
> The soft max_sectors limit is normally capped by the hardware limits and
> an arbitrary upper limit enforced by the kernel, but can be modified by
> the user.  A few drivers want to increase this limit (nbd, rbd) or
> adjust it up or down based on hardware capabilities (sd).
> 
> Change blk_validate_limits to default max_sectors to the optimal I/O
> size, or upgrade it to the preferred minimal I/O size if that is
> larger than the kernel default if no optimal I/O size is provided based
> on the logic in the SD driver.
> 
> This keeps the existing kernel default for drivers that do not provide
> an io_opt or very big io_min value, but picks a much more useful
> default for those who provide these hints, and allows to remove the
> hacks to set the user max_sectors limit in nbd, rbd and sd.
> 
> Note that rd picks a different value for the optimal I/O size vs the
             ^^
             rbd?

> user max_sectors value, so this is a bit of a behavior change that
> could use careful review from people familiar with rbd.

Anyway:

Reviewed-by: Bart Van Assche <bvanassche at acm.org>