On Sat, Mar 23, 2019 at 10:52:49PM -0400, Qian Cai wrote:
> On 3/23/19 10:06 PM, Matthew Wilcox wrote:
> > Thanks for testing. Kirill suggests this would be a better fix:
> >
> > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> > index 41858a3744b4..9718393ae45b 100644
> > --- a/include/linux/pagemap.h
> > +++ b/include/linux/pagemap.h
> > @@ -334,10 +334,12 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
> >
> > static inline struct page *find_subpage(struct page *page, pgoff_t offset)
> > {
> > + unsigned long index = page_index(page);
> > +
> > VM_BUG_ON_PAGE(PageTail(page), page);
> > - VM_BUG_ON_PAGE(page->index > offset, page);
> > - VM_BUG_ON_PAGE(page->index + compound_nr(page) <= offset, page);
> > - return page - page->index + offset;
> > + VM_BUG_ON_PAGE(index > offset, page);
> > + VM_BUG_ON_PAGE(index + compound_nr(page) <= offset, page);
> > + return page - index + offset;
> > }
> >
> > struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);
>
> This is not even compiled.
>
> If "s/compound_nr/compound_order/", it failed to boot here,
Oh, sorry. I have another patch in that tree.
- VM_BUG_ON_PAGE(page->index + (1 << compound_order(page)) <= offset,
- page);
+ VM_BUG_ON_PAGE(page->index + compound_nr(page) <= offset, page);
The patch for you should have looked like this:
@@ -335,11 +335,12 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
static inline struct page *find_subpage(struct page *page, pgoff_t offset)
{
+ unsigned long index = page_index(page);
+
VM_BUG_ON_PAGE(PageTail(page), page);
- VM_BUG_ON_PAGE(page->index > offset, page);
- VM_BUG_ON_PAGE(page->index + (1 << compound_order(page)) <= offset,
- page);
- return page - page->index + offset;
+ VM_BUG_ON_PAGE(index > offset, page);
+ VM_BUG_ON_PAGE(index + (1 << compound_order(page)) <= offset, page);
+ return page - index + offset;
}
> [ 56.915812] page dumped because: VM_BUG_ON_PAGE(index + compound_order(page)
> <= offset)
Yeah, you were missing the '1 <<' part.
