Re: [GIT PULL] Block updates for 6.9-rc1

[Mike Snitzer <snitzer@kernel.org>]

On Tue, Mar 12 2024 at  6:30P -0400,
Christoph Hellwig <hch@infradead.org> wrote:

> On Tue, Mar 12, 2024 at 06:22:21PM -0400, Mike Snitzer wrote:
> > > The real problem is that we combine the limits while we shouldn't.
> > > Every since we've supported immutable biovecs and do the splitting
> > > down in blk-mq there is no point to even inherit such limits in the
> > > upper drivers.
> > 
> > immutable biovecs, late splitting and blk-mq aren't a factor.
> > 
> > dm-crypt has to contend with the crypto subsystem and HW crypto
> > engines that have their own constraints.
> 
> Yes, they are.  The limit for underlying device does not matter for
> an upper devіce as it will split later.  And that's not just my
> opinion, you also clearly stated that in the commit adding the
> limits (586b286b110e94e).  We should have stopped inheriting all
> these limits only relevant for splitting when we switched to
> immutable bvecs.  I don't know why we didn't, but a big part of
> that might be that we never made clear which limits these are.

Wow, using my 8+ year old commit message against me ;)

I've honestly paged most of this out but I'll revisit, likely with
Mikulas, to pin this down better and then see what possible.