From: Marco Stornelli Subject: Re: [PATCH, RFC] xip: use i_mutex for xip_file_fault Date: Sun, 11 Sep 2011 10:25:03 +0200 Message-ID: <4E6C705F.8010101@gmail.com> References: <4E6B82DB.50803@gmail.com> <20110910155639.GY2203@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Linux FS Devel , Linux Kernel To: Al Viro Return-path: Received: from mail-fx0-f46.google.com ([209.85.161.46]:42573 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752546Ab1IKIbT (ORCPT ); Sun, 11 Sep 2011 04:31:19 -0400 In-Reply-To: <20110910155639.GY2203@ZenIV.linux.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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 >> >> 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