Re: kernel BUG at mm/swap.c:134! - page dumped because: VM_BUG_ON_PAGE(page_mapcount(page) != 0)

["Kirill A. Shutemov" <kirill@shutemov.name>]

On Wed, Apr 22, 2015 at 03:12:19PM +0200, Borislav Petkov wrote:
> On Sun, Apr 19, 2015 at 12:08:03AM +0200, Borislav Petkov wrote:
> > On Sat, Apr 18, 2015 at 05:59:53PM -0400, Linus Torvalds wrote:
> > > On Sat, Apr 18, 2015 at 5:56 PM, Kirill A. Shutemov
> > > <kirill@shutemov.name> wrote:
> > > >
> > > > Andrea has already seen the bug and pointed to 8d63d99a5dfb as possible
> > > > cause. I don't see why the commit could broke anything, but it worth
> > > > trying to revert and test.
> > > 
> > > Ahh, yes, that does look like a more likely culprit.
> > 
> > Reverted and building... will report in the next days.
> 
> FWIW, box is solid with the revert and has an uptime of ~4 days so far
> without hickups.

Could you try patch below instead? This can give a clue what's going on.

diff --git a/mm/swap.c b/mm/swap.c
index a7251a8ed532..0dff7004aa25 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -131,7 +131,11 @@ void put_unrefcounted_compound_page(struct page *page_head, struct page *page)
 		 * here, see the comment above this function.
 		 */
 		VM_BUG_ON_PAGE(!PageHead(page_head), page_head);
-		VM_BUG_ON_PAGE(page_mapcount(page) != 0, page);
+		if (page_mapcount(page) != 0) {
+			dump_page(page_head, NULL);
+			dump_page(page, NULL);
+			BUG();
+		}
 		if (put_page_testzero(page_head)) {
 			/*
 			 * If this is the tail of a slab THP page,
-- 
 Kirill A. Shutemov

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