On Sun, 27 Jun 2010, Tejun Heo wrote:
> >> struct pcpu_alloc_info * __init pcpu_build_alloc_info(
> >> - size_t reserved_size, ssize_t dyn_size,
> >> + size_t reserved_size, size_t dyn_size,
> >> size_t atom_size,
> >> pcpu_fc_cpu_distance_fn_t cpu_distance_fn)
> >> {
> >> @@ -1098,13 +1084,15 @@ struct pcpu_alloc_info * __init pcpu_bui
> >> memset(group_map, 0, sizeof(group_map));
> >> memset(group_cnt, 0, sizeof(group_map));
> >>
> >> + size_sum = PFN_ALIGN(static_size + reserved_size + dyn_size);
> >> + dyn_size = size_sum - static_size - reserved_size;
> >
> > Ok, so the only purpose of "dyn_size" is to store in the struct
> > pcpu_alloc_info later. Before this patch, ai->dyn_size would always be 0
> > if that's what was passed to pcpu_build_alloc_info(), but due to this
> > arithmetic it now requires that static_size + reserved_size to be pfn
> > aligned. Where is that enforced or do we not care?
>
> I'm not really following you, but
>
> * Nobody called pcpu_build_alloc_info() w/ zero dyn_size. It was
> either -1 or positive minimum size.
>
Ok, the commit description said that passing pcpu_build_alloc_info() a
dyn_size of 0 would force it to be 0, although the arithmetic introduced
by this patch would not have necessarily set ai->dyn_size to be 0 when
passed if static_size + reserved_size was not page aligned (size_sum
could be greater than static_size + reserved_size). Since there are no
users passing a dyn_size of 0, my concern is addressed.
Thanks!
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