linux-kernel - Re: Status of buffered write path (deadlock fixes)

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Message-ID: <457D6944.4010703@yahoo.com.au>
Date:	Tue, 12 Dec 2006 01:20:52 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Mark Fasheh <mark.fasheh@...cle.com>
CC:	Linux Memory Management <linux-mm@...ck.org>,
	linux-fsdevel@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	Andrew Morton <akpm@...gle.com>
Subject: Re: Status of buffered write path (deadlock fixes)

Nick Piggin wrote:
> Mark Fasheh wrote:

>> If we make the change I described above (looking for BH_New buffers 
>> outside
>> the range passed), then zero length or partial shouldn't matter, but zero
>> length instead of partial would be nicer imho just for the sake of 
>> reducing
>> the total number of cases down to the entire range or zero length.
> 
> 
> We don't want to do zero length, because we might make the theoretical
> livelock much easier to hit (eg. in the case of many small iovecs). But
> yes we can restrict ourselves to zero-length or full-length.

On second thoughts, I think I'm wrong about that.

Consider the last page of a file, which is uptodate. A full length
commit, which extends the file, will expose transient zeroes if the
usercopy fails.

-- 
SUSE Labs, Novell Inc.
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