On Thu, Apr 04, 2019 at 09:10:10AM -0400, Qian Cai wrote:
> On Mon, 2019-04-01 at 12:27 +0300, Kirill A. Shutemov wrote:
> > What about patch like this? (completely untested)
> >
> > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> > index f939e004c5d1..e3b9bf843dcb 100644
> > --- a/include/linux/pagemap.h
> > +++ b/include/linux/pagemap.h
> > @@ -335,12 +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);
> > + unsigned long mask;
> >
> > VM_BUG_ON_PAGE(PageTail(page), page);
> > - VM_BUG_ON_PAGE(index > offset, page);
> > - VM_BUG_ON_PAGE(index + (1 << compound_order(page)) <= offset, page);
> > - return page - index + offset;
> > +
> > + mask = (1UL << compound_order(page)) - 1;
> > + return page + (offset & mask);
> > }
> >
> > struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);
>
> No, this then leads to a panic below by LTP hugemmap05. Still reverting the
> whole "mm: page cache: store only head pages in i_pages" commit fixed the
> problem.
Ughh... hugetlb stores pages in page cache differently.
What about this:
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index f939e004c5d1..2e8438a1216a 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -335,12 +335,15 @@ 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);
+ unsigned long mask;
+
+ if (PageHuge(page))
+ return page;
VM_BUG_ON_PAGE(PageTail(page), page);
- VM_BUG_ON_PAGE(index > offset, page);
- VM_BUG_ON_PAGE(index + (1 << compound_order(page)) <= offset, page);
- return page - index + offset;
+
+ mask = (1UL << compound_order(page)) - 1;
+ return page + (offset & mask);
}
struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);
--
Kirill A. Shutemov
