Re: [PATCH] padata: Fix possible divide-by-0 panic in padata_mt_helper()

[Waiman Long]

On 8/10/24 23:13, Herbert Xu wrote:
> On Sat, Aug 10, 2024 at 11:11:07PM -0400, Waiman Long wrote:
> > > Unless I'm missing something chunk_size cannot be zero before the
> > > division because that's the first thing we check upon entry into
> > > this function.
> > chunk_size is initialized as
> >
> > ps.chunk_size = job->size / (ps.nworks * load_balance_factor);
> >
> > chunk_size will be 0 if job->size < (ps.nworks * load_balance_factor). If
> > min_chunk is 0, chunk_size will remain 0.
> That's why I was suggesting that you replace the division by
> DIV_ROUND_UP.  That should ensure that ps.chunk_size is not zero.

Now I see what you mean. Yes, we can probably change that to a 
DIV_ROUND_UP operation to make sure that chunk_size is at least one 
unless job->size is 0. I still think the current patch is a bit more 
fail-safe.

Cheers, Longman