linux-kernel - Re: [PATCH] [8/18] BKL-removal: Remove BKL from remote

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Date:	Mon, 28 Jan 2008 09:17:52 +0100
From:	Andi Kleen <ak@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Trond Myklebust <Trond.Myklebust@...app.com>,
	Steve French <smfrench@...il.com>, swhiteho@...hat.com,
	sfrench@...ba.org, vandrove@...cvut.cz,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] [8/18] BKL-removal: Remove BKL from remote_llseek

> I completely agree.  If one thread writes A and another writes B then the
> kernel should record either A or B, not ((A & 0xffffffff00000000) | (B &
> 0xffffffff))

The problem is pretty nasty unfortunately. To solve it properly I think
the file_operations->read/write prototypes would need to be changed
because otherwise it is not possible to do atomic relative updates
of f_pos. Right now the actual update is burrowed deeply in the low level 
read/write implementation. But that would be a huge impact all over
the tree :/

Or maybe define a new read/write64 and keep the default as 32bit only-- i 
suppose most users don't really need 64bit. Still would be a nasty API 
change.

-Andi
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