Re: [RFC 0/2] guarantee natural alignment for kmalloc()

[Christoph Hellwig]

On Fri, Apr 05, 2019 at 07:11:17PM +0200, Vlastimil Babka wrote:
> On 3/22/19 6:52 PM, Christopher Lameter wrote:
> > On Thu, 21 Mar 2019, Vlastimil Babka wrote:
> > 
> >> That however doesn't work well for the xfs/IO case where block sizes are
> >> not known in advance:
> >>
> >> https://lore.kernel.org/linux-fsdevel/20190225040904.5557-1-ming.lei@xxxxxxxxxx/T/#ec3a292c358d05a6b29cc4a9ce3ae6b2faf31a23f
> > 
> > I thought we agreed to use custom slab caches for that?
> 
> Hm maybe I missed something but my impression was that xfs/IO folks would have
> to create lots of them for various sizes not known in advance, and that it
> wasn't practical and would welcome if kmalloc just guaranteed the alignment.
> But so far they haven't chimed in here in this thread, so I guess I'm wrong.

Yes, in XFS we might have quite a few.  Never mind all the other
block level consumers that might have similar reasonable expectations
but haven't triggered the problematic drivers yet.