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Date: Tue, 3 Aug 2010 21:22:16 +0800
From: Wu Fengguang <fengguang.wu@intel.com>
To: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Dave Chinner <david@fromorbit.com>,
        Chris Mason <chris.mason@oracle.com>, Nick Piggin <npiggin@suse.de>,
        Rik van Riel <riel@redhat.com>, Johannes Weiner <hannes@cmpxchg.org>,
        Christoph Hellwig <hch@infradead.org>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Andrea Arcangeli <aarcange@redhat.com>, Mel Gorman <mel@csn.ul.ie>,
        Minchan Kim <minchan.kim@gmail.com>
Subject: Re: [PATCH 2/5] writeback: stop periodic/background work on seeing
 sync works
Message-ID: <20100803132216.GA31893@localhost>
References: <20100729115142.102255590@intel.com>
 <20100729121423.332557547@intel.com>
 <20100729162027.GF12690@quack.suse.cz>
 <20100730040306.GA5694@localhost>
 <20100802205152.GL3278@quack.suse.cz>
 <20100803030125.GA12070@localhost>
 <20100803105520.GA3322@quack.suse.cz>
 <20100803123922.GC3322@quack.suse.cz>
 <20100803125924.GA31827@localhost>
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> >   Fengguang, how about merging also the attached simple patch together with
> > my fix? With these two patches, I'm not able to trigger any sync livelock
> > while without one of them I hit them quite easily...
> 
> This looks OK. However note that redirty_tail() can modify
> dirtied_when unexpectedly. So the more we rely on wb_start, the more
> possibility an inode is (wrongly) skipped by sync. I have a bunch of
> patches to remove redirty_tail(). However they may not be good
> candidates for 2.6.36..

It looks that setting wb_start at the beginning of
writeback_inodes_wb() won't be easily affected by redirty_tail().

So

Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>

Thanks,
Fengguang