From: Andi Kleen <ak@suse.de>
Subject: Re: [PATCH] [8/18] BKL-removal: Remove BKL from remote_llseek
Date: Mon, 28 Jan 2008 14:27:35 +0100
Message-ID: <200801281427.36048.ak@suse.de>
References: <20080127317.043953000@suse.de> <20080127211345.6e73fa0b.akpm@linux-foundation.org> <20080128125605.299740a1@core>
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Cc: Andrew Morton <akpm@linux-foundation.org>,
	Trond Myklebust <Trond.Myklebust@netapp.com>,
	Steve French <smfrench@gmail.com>, swhiteho@redhat.com,
	sfrench@samba.org, vandrove@vc.cvut.cz,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
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On Monday 28 January 2008 13:56:05 Alan Cox wrote:
> > > No specific spec, just general quality of implementation.
> > 
> > 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))
> 
> Agree entirely: the spec doesn't allow for random scribbling in the wrong
> place. It doesn't cover which goes first or who "wins" the race but
> provides pwrite/pread for that situation. Writing somewhere unrelated is
> definitely not to spec 

Actually it would probably -- i guess it's undefined and in undefined
country such things can happen.

Also to be fair I think it's only a problem for the 4GB wrapping case
which is presumably rare (otherwise we would have heard about it)

Also worse really fixing it would be a major change to the VFS 
because of the way ->read/write are defined :/

-Andi