Re: brd in a memdesc world

[Matthew Wilcox <willy@infradead.org>]

On Wed, Mar 13, 2024 at 07:36:01PM +0100, Pankaj Raghav wrote:
> Got it! Probably moving to folios just for the sake of retaining the
> debugging checks is not enough.

That would be my assessment, but maybe Jens has a different preference.

> > None of those things are needed for brd's uses.  All brd needs is to
> > be able to allocate, kmap and free chunks of memory.  Unless there are
> > plans to do more than this.
> 
> I remember he mentioned he wanted to support bigger logical block sizes
> in brd, in which case moving to folios might be justified.

Using folios (or some other data structure that embedded the order of
the allocation) would be justified if there was a proposal on the table
to support variable sized allocations in the brd XArray.  Hannes wasn't
suggesting that; his patch series used a fixed size per block device
(which honestly makes sense; I don't see the advantage to supporting
variable sized allocations).