Re: [PATCH v2 2/2] mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two)

Ming Lei
2019-09-04T06:41:01Z

On Wed, Sep 04, 2019 at 07:19:33AM +0200, Christoph Hellwig wrote:
> On Tue, Sep 03, 2019 at 01:53:12PM -0700, Matthew Wilcox wrote:
> > > Its enabled in all full debug session as far as I know. Fedora for
> > > example has been running this for ages to find breakage in device drivers
> > > etc etc.
> >
> > Are you telling me nobody uses the ramdisk driver on fedora? Because
> > that's one of the affected drivers.
>
> For pmem/brd misaligned memory alone doesn't seem to be the problem.
> Misaligned memory that cross a page barrier is. And at least XFS
> before my log recovery changes only used kmalloc for smaller than
> page size allocation, so this case probably didn't hit.

BTW, does sl[aou]b guarantee that smaller than page size allocation via kmalloc()
won't cross page boundary any time?

Thanks,
Ming