Re: Race in pagevec_strip?

[Christoph Lameter <clameter@sgi.com>]

On Thu, 16 Mar 2006, Hugh Dickins wrote:

> But wouldn't you, on balance, be better off repeating the
> PagePrivate test within the lock?

Good idea. That avoid uselessly taking the pagelock.



Seems that we can call try_to_release_page with PagePrivate off and a
valid mapping because we check PagePrivate before taking the page lock.
This may cause all sorts of trouble for thefilesystem *_releasepage()
handlers. XFS bombs out in that case.

Check the PagePrivate again before calling try_to_release_page.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.16-rc6/mm/swap.c
===================================================================
--- linux-2.6.16-rc6.orig/mm/swap.c	2006-03-11 14:12:55.000000000 -0800
+++ linux-2.6.16-rc6/mm/swap.c	2006-03-16 11:46:54.000000000 -0800
@@ -393,7 +393,8 @@ void pagevec_strip(struct pagevec *pvec)
 		struct page *page = pvec->pages[i];
 
 		if (PagePrivate(page) && !TestSetPageLocked(page)) {
-			try_to_release_page(page, 0);
+			if (PagePrivate(page))
+				try_to_release_page(page, 0);
 			unlock_page(page);
 		}
 	}