On Wed, 2006-09-13 at 18:22 -0700, Zachary Amsden wrote:
> Martin Schwidefsky wrote:
> > diff -urpN linux-2.6/mm/memory.c linux-2.6-patched/mm/memory.c
> > --- linux-2.6/mm/memory.c 2006-09-01 12:50:24.000000000 +0200
> > +++ linux-2.6-patched/mm/memory.c 2006-09-01 12:50:24.000000000 +0200
> > @@ -2523,6 +2523,31 @@ int make_pages_present(unsigned long add
> > BUG_ON(addr >= end);
> > BUG_ON(end > vma->vm_end);
> > len = (end+PAGE_SIZE-1)/PAGE_SIZE-addr/PAGE_SIZE;
> > +
> > + if (page_host_discards() && (vma->vm_flags & VM_LOCKED)) {
> > + int rlen = len;
> > + ret = 0;
> > + while (rlen > 0) {
> > + struct page *page_refs[32];
> > + int chunk, cret, i;
> > +
> > + chunk = rlen < 32 ? rlen : 32;
> > + cret = get_user_pages(current, current->mm, addr,
> > + chunk, write, 0,
> > + page_refs, NULL);
> > + if (cret > 0) {
> > + for (i = 0; i < cret; i++)
> > + page_cache_release(page_refs[i]);
> > + ret += cret;
> > + }
> > + if (cret < chunk)
> > + return ret ? : cret;
> > + addr += 32*PAGE_SIZE;
> > + rlen -= 32;
> > + }
> > + return ret == len ? 0 : -1;
> > + }
> > +
> > ret = get_user_pages(current, current->mm, addr,
> > len, write, 0, NULL, NULL);
> > if (ret < 0)
> >
>
> This seems like a bit of unneeded complexity. Since you've already
> changed get_user_pages, why not add a follow flag to release the page
> cache, and simply pass it to get_user_pages, instead of trying to fetch
> the page list back. In particular, write and force arguments to
> get_user_pages look very ripe for combining into a flags field. Sure,
> get_user_pages now has a bit more work to do, but it is already a
> monster, and I think it would keep make_page_present much cleaner.
That makes sense. If we combine write and force the additional flag we
need won't hurt. I'll add this to my to-do list.
--
blue skies,
Martin.
Martin Schwidefsky
Linux for zSeries Development & Services
IBM Deutschland Entwicklung GmbH
"Reality continues to ruin my life." - Calvin.
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