[PATCH 05/15] block: add a max_user_discard_sectors queue limit

[Keith Busch]

On Mon, Jan 22, 2024 at 07:38:57PM +0100, Christoph Hellwig wrote:
> On Mon, Jan 22, 2024 at 11:27:15AM -0700, Keith Busch wrote:
> > > +	q->limits.max_user_discard_sectors = max_discard_bytes >> SECTOR_SHIFT;
> > > +	q->limits.max_discard_sectors =
> > > +		min_not_zero(q->limits.max_hw_discard_sectors,
> > > +			     q->limits.max_user_discard_sectors);
> > 
> > Shouldn't writing 0 disable discards?
> 
> I mirror the max_user_sectors behavior here, where 0 disables the
> user limiting.  But yes, that would be a behavior change.

But a user should be able to disable discards, right? Unless you really
want to match max_user_sectors, I think you could default the user
setting here to UINT_MAX and use "min" instead of "min_not_zero".