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

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Date:	Mon, 28 Jan 2008 03:43:27 +0100
From:	Andi Kleen <ak@...e.de>
To:	"Steve French" <smfrench@...il.com>
Cc:	Trond.Myklebust@...app.com, swhiteho@...hat.com, sfrench@...ba.org,
	vandrove@...cvut.cz, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, akpm@...l.org
Subject: Re: [PATCH] [8/18] BKL-removal: Remove BKL from remote_llseek

On Sunday 27 January 2008 17:57:14 Steve French wrote:
> Don't you need to a spinlock/spinunlock(i_lock) or something similar
> (there isn't a spinlock in the file struct unfortunately) around the
> reads and writes from f_pos in fs/read_write.c in remote_llseek with
> your patch since the reads/writes from that field are not necessarily
> atomic and threads could be racing in seek on the same file struct?

Funny that you mention it. I actually noticed this too while working on this, 
but noticed that it is wrong everywhere (as in even plain sys_write/read gets 
it wrong). So I decided to not address it because it is already
broken. 

I did actually send email to a few people about this, but no answer
yet.

I agree it's probably all broken on 32bit platforms, but I'm not
sure how to best address this. When it is comprehensively addressed remote_llseek 
can use that new method too.

-Andi

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