linux-kernel - Re: [PATCH, RFC] xip: use i_mutex for xip_file

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Message-ID: <20110910155639.GY2203@ZenIV.linux.org.uk>
Date:	Sat, 10 Sep 2011 16:56:39 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Marco Stornelli <marco.stornelli@...il.com>
Cc:	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH, RFC] xip: use i_mutex for xip_file_fault

On Sat, Sep 10, 2011 at 05:31:39PM +0200, Marco Stornelli wrote:
> From: Marco Stornelli <marco.stornelli@...il.com>
> 
> There aren't sufficient sync points for a fs for xip operations. In 
> particular for the mmap case. It can be not sufficient to lock/unlock 
> to do some operation inside get_xip_mem callback. For xip_file_read 
> it's really easy to write a fs specific wrapper, xip_file_write hold 
> i_mutex so no problem. With this patch we can avoid concurrent truncate 
> operation and xip mmap.

Umm...  I really don't like that; what's going to happen if you have a file
mmapped and do write() to that file from address in that mapping?
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