Re: + iov_iter-iterate_folioq-fix-handling-of-offset-=-folio-size.patch added to mm-hotfixes-unstable branch

[Dominique Martinet <asmadeus@codewreck.org>]

David Howells wrote on Tue, Aug 12, 2025 at 10:38:07AM +0100:
> > @@ -168,6 +168,8 @@ size_t iterate_folioq(struct iov_iter *i
> >  			break;
> >  
> >  		fsize = folioq_folio_size(folioq, slot);
> > +		if (skip < fsize) {
> >  		base = kmap_local_folio(folio, skip);
> >  		part = umin(len, PAGE_SIZE - skip % PAGE_SIZE);
> >  		remain = step(base, progress, part, priv, priv2);
> > @@ -177,6 +179,7 @@ size_t iterate_folioq(struct iov_iter *i
> >  		progress += consumed;
> >  		skip += consumed;
> > +		}
> >  		if (skip >= fsize) {
> >  			skip = 0;
> >  			slot++;
> >  			if (slot == folioq_nr_slots(folioq) && folioq->next) {
> 
> With the stuff inside the braces suitably indented.  The compiler should be
> able to optimise away the extra comparison.

skip is modified in the first if so I don't see how the compiler could
optimize it.
I just checked and at least iov_iter.o is slightly bigger with a second if:

(a.o = goto, b.o = if)
06:17:52 asmadeus@thor 0 ~/code/linux/bb$ size a.o b.o
   text	  data	   bss	   dec	   hex	filename
  26923	  1104	     0	 28027	  6d7b	a.o
  27019	  1104	     0	 28123	  6ddb	b.o

but honestly I'm happy to focus on readability here -- if you think two
if are easier to read I'll be happy to send a v3

-- 
Dominique Martinet | Asmadeus