On Tue, Mar 15, 2016 at 03:40:53PM +0900, Sergey Senozhatsky wrote:
> On (03/11/16 16:30), Minchan Kim wrote:
> > -static void *location_to_obj(struct page *page, unsigned long obj_idx)
> > +static void objidx_to_page_and_ofs(struct size_class *class,
> > + struct page *first_page,
> > + unsigned long obj_idx,
> > + struct page **obj_page,
> > + unsigned long *ofs_in_page)
>
> this looks big; 5 params, function "returning" both page and offset...
> any chance to split it in two steps, perhaps?
Yes, it's rather ugly but I don't have a good idea.
Feel free to suggest if you have a better idea.
>
> besides, it is more intuitive (at least to me) when 'offset'
> shortened to 'offt', not 'ofs'.
Indeed. I will change it to get_page_and_offset instead of
abbreviation if we cannot refactor it more.
>
> -ss
>
> > {
> > - unsigned long obj;
> > + int i;
> > + unsigned long ofs;
> > + struct page *cursor;
> > + int nr_page;
> >
> > - if (!page) {
> > - VM_BUG_ON(obj_idx);
> > - return NULL;
> > - }
> > + ofs = obj_idx * class->size;
> > + cursor = first_page;
> > + nr_page = ofs >> PAGE_SHIFT;
> >
> > - obj = page_to_pfn(page) << OBJ_INDEX_BITS;
> > - obj |= ((obj_idx) & OBJ_INDEX_MASK);
> > - obj <<= OBJ_TAG_BITS;
> > + *ofs_in_page = ofs & ~PAGE_MASK;
> > +
> > + for (i = 0; i < nr_page; i++)
> > + cursor = get_next_page(cursor);
> >
> > - return (void *)obj;
> > + *obj_page = cursor;
> > }
