From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id F135C6B0055 for ; Thu, 15 Jan 2009 12:36:04 -0500 (EST) Date: Thu, 15 Jan 2009 11:35:45 -0600 (CST) From: Christoph Lameter Subject: Re: [patch] mm: fix assertion In-Reply-To: <20090114062816.GA15671@wotan.suse.de> Message-ID: References: <20090114062816.GA15671@wotan.suse.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Nick Piggin Cc: Linus Torvalds , Linux Memory Management List List-ID: You still have a VM_BUG_ON(PageTail(page)); in page_cache_get_speculative() which will verify that the successfully acquired speculative reference is not a compound tail. Reviewed-by: Christoph Lameter On Wed, 14 Jan 2009, Nick Piggin wrote: > (I ran into this when debugging the lockless pagecache barrier problem btw) > > -- > > This assertion is incorrect for lockless pagecache. By definition if we have an > unpinned page that we are trying to take a speculative reference to, it may > become the tail of a compound page at any time (if it is freed, then reallocated > as a compound page). > > It was still a valid assertion for the vmscan.c LRU isolation case, but it > doesn't seem incredibly helpful... if somebody wants it, they can put it back > directly where it applies in the vmscan code. > > Signed-off-by: Nick Piggin > --- > Index: linux-2.6/include/linux/mm.h > =================================================================== > --- linux-2.6.orig/include/linux/mm.h 2009-01-05 14:53:29.000000000 +1100 > +++ linux-2.6/include/linux/mm.h 2009-01-05 14:53:54.000000000 +1100 > @@ -270,7 +270,6 @@ static inline int put_page_testzero(stru > */ > static inline int get_page_unless_zero(struct page *page) > { > - VM_BUG_ON(PageTail(page)); > return atomic_inc_not_zero(&page->_count); > } > > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org