Re: [PATCH v2 1/4] mm: correct mask size for slub page->objects

[Kirill A. Shutemov]

On Thu, Sep 12, 2019 at 03:11:14PM -0600, Yu Zhao wrote:
> On Thu, Sep 12, 2019 at 12:40:35PM +0300, Kirill A. Shutemov wrote:
> > On Wed, Sep 11, 2019 at 08:31:08PM -0600, Yu Zhao wrote:
> > > Mask of slub objects per page shouldn't be larger than what
> > > page->objects can hold.
> > > 
> > > It requires more than 2^15 objects to hit the problem, and I don't
> > > think anybody would. It'd be nice to have the mask fixed, but not
> > > really worth cc'ing the stable.
> > > 
> > > Fixes: 50d5c41cd151 ("slub: Do not use frozen page flag but a bit in the page counters")
> > > Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
> > 
> > I don't think the patch fixes anything.
> 
> Technically it does. It makes no sense for a mask to have more bits
> than the variable that holds the masked value. I had to look up the
> commit history to find out why and go through the code to make sure
> it doesn't actually cause any problem.
> 
> My hope is that nobody else would have to go through the same trouble.

Just put some comments then.

-- 
 Kirill A. Shutemov