linux-kernel - Re: [PATCH 0/2] radix-tree: fix writeback livelock avoidance code

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Message-ID: <20100820135141.GC5716@quack.suse.cz>
Date:	Fri, 20 Aug 2010 15:51:41 +0200
From:	Jan Kara <jack@...e.cz>
To:	Dave Chinner <david@...morbit.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	jack@...e.cz, npiggin@...nel.dk
Subject: Re: [PATCH 0/2] radix-tree: fix writeback livelock avoidance code

On Fri 20-08-10 15:22:05, Dave Chinner wrote:
> The following two patches fix bugs in the new radix tree functionality used to
> implement the writeback livelock avoidance code. Both bugs manifest themselves
> as stray PAGECACHE_TAG_TOWRITE tags in the mapping->page_tree radix tree
> resulting in livelocks during tag lookups. More subtly, they also appear to
> result in writeback tree walks occasionally terminating early and so not
> actually writing all the pages they are supposed to.
  Really, how that early termination could happen? I'm just wondering
because I don't see that.. The code just mindlessly copies tags regardless
of how target flags are set so that's why I'd think that any stale copied
flags just don't matter...

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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