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

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Message-ID: <4E6C705F.8010101@gmail.com>
Date:	Sun, 11 Sep 2011 10:25:03 +0200
From:	Marco Stornelli <marco.stornelli@...il.com>
To:	Al Viro <viro@...IV.linux.org.uk>
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

Il 10/09/2011 17:56, Al Viro ha scritto:
> 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?
>

Nothing strange. There is a serialization of the operations. Maybe I 
don't understand the point here.

Marco
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