linux-kernel - Re: [PATCH v4 2/7] deactivate invalidated pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20101207150710.GA26613@barrios-desktop>
Date:	Wed, 8 Dec 2010 00:07:10 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Nick Piggin <npiggin@...nel.dk>, Mel Gorman <mel@....ul.ie>
Subject: Re: [PATCH v4 2/7] deactivate invalidated pages

On Tue, Dec 07, 2010 at 03:49:24PM +0100, Johannes Weiner wrote:
> On Mon, Dec 06, 2010 at 02:29:10AM +0900, Minchan Kim wrote:
> > Changelog since v3:
> >  - Change function comments - suggested by Johannes
> >  - Change function name - suggested by Johannes
> >  - add only dirty/writeback pages to deactive pagevec
> 
> Why the extra check?
> 
> > @@ -359,8 +360,16 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
> >  			if (lock_failed)
> >  				continue;
> >  
> > -			ret += invalidate_inode_page(page);
> > -
> > +			ret = invalidate_inode_page(page);
> > +			/*
> > +			 * If the page is dirty or under writeback, we can not
> > +			 * invalidate it now.  But we assume that attempted
> > +			 * invalidation is a hint that the page is no longer
> > +			 * of interest and try to speed up its reclaim.
> > +			 */
> > +			if (!ret && (PageDirty(page) || PageWriteback(page)))
> > +				deactivate_page(page);
> 
> The writeback completion handler does not take the page lock, so you
> can still miss pages that finish writeback before this test, no?

Yes. but I think it's rare and even though it happens, it's not critical.
> 
> Can you explain why you felt the need to add these checks?

invalidate_inode_page can return 0 although the pages is !{dirty|writeback}.
Look invalidate_complete_page. As easiest example, if the page has buffer and
try_to_release_page can't release the buffer, it could return 0.

I want to check this.

> 
> Thanks!
> 
> 	Hannes

-- 
Kind regards,
Minchan Kim
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/