Date: Tue, 5 Jan 2010 08:10:21 -0800 (PST)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
cc: Peter Zijlstra <peterz@infradead.org>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "linux-mm@kvack.org" <linux-mm@kvack.org>,
       "minchan.kim@gmail.com" <minchan.kim@gmail.com>,
       cl@linux-foundation.org, "hugh.dickins" <hugh.dickins@tiscali.co.uk>,
       Nick Piggin <nickpiggin@yahoo.com.au>, Ingo Molnar <mingo@elte.hu>
Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault()
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On Tue, 5 Jan 2010, Al Viro wrote:
> 
> - a bunch of fs operations done from RCU callbacks.  Including severely
> blocking ones.

Yeah, you're right (and Peter also pointed out the might_sleep). That is 
likely to be the really fundamental issue. 

You _can_ handle it (make the RCU callback just schedule the work instead 
of doing it directly), but it does sound really nasty. I suspect we should 
explore just about any other approach over this one. 

			Linus
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