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: <20110907065635.GA12619@lst.de>
Date:	Wed, 7 Sep 2011 08:56:35 +0200
From:	Christoph Hellwig <hch@....de>
To:	Jan Kara <jack@...e.cz>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Wu Fengguang <fengguang.wu@...el.com>,
	linux-fsdevel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@....de>,
	Dave Chinner <david@...morbit.com>,
	Greg Thelen <gthelen@...gle.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Andrea Righi <arighi@...eler.com>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 17/18] writeback: fix dirtied pages accounting on
	redirty

On Wed, Sep 07, 2011 at 02:22:22AM +0200, Jan Kara wrote:
> > So wtf is ext4 doing? Shouldn't a page stay dirty until its written out?
> > 
> > That is, should we really frob around this behaviour or fix ext4 because
> > its on crack?
>   Fengguang, could you please verify your findings with recent kernel? I
> believe ext4 got fixed in this regard some time ago already (and yes, old
> delalloc writeback code in ext4 was terrible).

The pattern we do in writeback is:

in pageout / write_cache_pages:
	lock_page();
	clear_page_dirty_for_io();

in ->writepage:
	set_page_writeback();
	unlock_page();
	end_page_writeback();

So whenever ->writepage decides it doesn't want to write things back
we have to redirty pages.  We have this happen quite a bit in every
filesystem, but ext4 hits it a lot more than usual because it refuses
to write out delalloc pages from plain ->writepage and only allows
->writepages to do it.

--
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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ