On Thu, 9 Nov 2023 01:12:15 +0100 Andreas Grünbacher <andreas.gruenbacher@xxxxxxxxx> wrote:
> Andrew,
>
> Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> schrieb am Do., 9. Nov. 2023, 00:06:
> > > +
> > > + if (folio_test_highmem(folio)) {
> > > + size_t max = PAGE_SIZE - offset_in_page(offset);
> > > +
> > > + while (len > max) {
> >
> > Shouldn't this be `while (len)'? AFAICT this code can fail to clear
> > the final page.
>
> not sure what you're seeing there, but this looks fine to me.
I was right! This code does fail to handle the final page.
: static inline void folio_fill_tail(struct folio *folio, size_t offset,
: const char *from, size_t len)
: {
: char *to = kmap_local_folio(folio, offset);
:
: VM_BUG_ON(offset + len > folio_size(folio));
:
: if (folio_test_highmem(folio)) {
: size_t max = PAGE_SIZE - offset_in_page(offset);
:
: while (len > max) {
: memcpy(to, from, max);
: kunmap_local(to);
: len -= max;
: from += max;
: offset += max;
: max = PAGE_SIZE;
: to = kmap_local_folio(folio, offset);
: }
: }
:
: memcpy(to, from, len);
This code down here handles it, doh.
: to = folio_zero_tail(folio, offset, to);
: kunmap_local(to);
: }
Implementation seems less straightforward than it might be? Oh well.
Has it been runtime tested?
Anyway, let's please change the function argument ordering and remember
to cc linux-mm on v2?
