On Tue, 2024-02-27 at 07:02 +0000, Christophe Leroy wrote:

quoted

It could be possible to initialize the new field for each arch to
0, but
instead simply inialize the field with a C99 struct inializing
syntax.

Why doing a full init of the struct when all fields are re-written a
few 
lines after ?

If I take the exemple of powerpc function slice_find_area_bottomup():

        struct vm_unmapped_area_info info;

        info.flags = 0;
        info.length = len;
        info.align_mask = PAGE_MASK & ((1ul << pshift) - 1);
        info.align_offset = 0;

For me it looks better to just add:

        info.new_field = 0; /* or whatever value it needs to have */

Hi,

Thanks for taking a look. Yes, I guess that should have some
justification. I was thinking of two reasons:
1. No future additions of optional parameters would need to make tree
wide changes like this.
2. The change is easier to review and get correct because the necessary
context is within a single line. For example, in that function some of
members are set within a while loop. The place you pointed seems to be
the correct one, but a diff that had the new field set after:
   info.high_limit = addr;
...would look correct too, but not be.

What is the concern with C99 initialization? FWIW, the full series also
removes an indirect branch, and probably is a net win for performance
in this path.