linux-kernel - Re: [PATCH 5/9] writeback: introduce the pageout work

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Date:	Fri, 9 Mar 2012 10:51:35 +0100
From:	Jan Kara <jack@...e.cz>
To:	Fengguang Wu <fengguang.wu@...el.com>
Cc:	Artem Bityutskiy <dedekind1@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kara <jack@...e.cz>, Greg Thelen <gthelen@...gle.com>,
	Ying Han <yinghan@...gle.com>,
	"hannes@...xchg.org" <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Minchan Kim <minchan.kim@...il.com>,
	Linux Memory Management List <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH 5/9] writeback: introduce the pageout work

  Hello,

On Thu 08-03-12 23:31:13, Wu Fengguang wrote:
> On Wed, Mar 07, 2012 at 05:48:21PM +0200, Artem Bityutskiy wrote:
> > On Sat, 2012-03-03 at 21:55 +0800, Fengguang Wu wrote:
> > >   13   1125  /c/linux/fs/ubifs/file.c <<do_truncation>>   <===== deadlockable
> > 
> > Sorry, but could you please explain once again how the deadlock may
> > happen?
> 
> Sorry I confused ubifs do_truncation() with the truncate_inode_pages()
> that may be called from iput().
> 
> The once suspected deadlock scheme is when the flusher thread calls
> the final iput:
> 
>         flusher thread
>           iput_final
>             <some ubifs function>
>               ubifs_budget_space
>                 shrink_liability
>                   writeback_inodes_sb
>                     writeback_inodes_sb_nr
>                       bdi_queue_work
>                       wait_for_completion  => end up waiting for the flusher itself
> 
> However I cannot find any ubifs functions to form the above loop, so
> ubifs should be safe for now.
  Yeah, me neither but I also failed to find a place where
ubifs_evict_inode() truncates inode space when deleting the inode... Artem?

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