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

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Date:	Wed, 25 Aug 2010 22:11:26 +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.
> 
> Please review and test - these are pretty serious problems for the writeback code.
  OK, I've updated Andrew's radix tree test suite to use the latest
incarnation of radix-tree.c and added check to verify consistency of tags
in a radix tree. Without your patches, the new error check triggers almost
immediately for radix_tree_range_tag_if_tagged, with them the test passes.

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