Re: fuse: trying to steal weird page

[Matthew Wilcox <willy@infradead.org>]

On Sat, May 02, 2020 at 08:52:48PM +0100, Nikolaus Rath wrote:
> On May 02 2020, Nikolaus Rath <Nikolaus@rath.org> wrote:
> > I have recently noticed that a FUSE filesystem regularly produces many
> > kernel messages like this:
> >
> > [ 2333.009931] fuse: trying to steal weird page
> > [ 2333.009937] fuse: page=00000000dd1750e3 index=2022240 flags=17ffffc0000097, count=1,
> > mapcount=0, mapping=00000000125079ad
...
> > What are the implications of the above kernel message? Is there a way to
> > provide more debugging information?

It'd be helpful to use the common debugging infrastructure which prints
more useful information:

+++ b/fs/fuse/dev.c
@@ -772,8 +772,7 @@ static int fuse_check_page(struct page *page)
               1 << PG_lru |
               1 << PG_active |
               1 << PG_reclaim))) {
-               pr_warn("trying to steal weird page\n");
-               pr_warn("  page=%p index=%li flags=%08lx, count=%i, mapcount=%i, mapping=%p\n", page, page->index, page->flags, page_count(page), page_mapcount(page), page->mapping);
+               dump_page(page, "fuse: trying to steal weird page");
                return 1;
        }
        return 0;

(whitespace damaged; if you can't make the equivalent change, let me
know and I'll send you a real patch)