From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Paris Subject: Re: A possible flaw in the fsnotify design. Date: Mon, 15 Nov 2010 17:51:58 -0500 Message-ID: <1289861518.14282.41.camel@localhost.localdomain> References: <1289859078.14282.28.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Tvrtko Ursulin , linux-fsdevel@vger.kernel.org, "stefan@buettcher.org" , linux-kernel@vger.kernel.org, Al Viro To: Alexey Zaytsev Return-path: Received: from mx1.redhat.com ([209.132.183.28]:58934 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758016Ab0KOWwF (ORCPT ); Mon, 15 Nov 2010 17:52:05 -0500 In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, 2010-11-16 at 01:44 +0300, Alexey Zaytsev wrote: > On Tue, Nov 16, 2010 at 01:11, Eric Paris wrote: > > On Tue, 2010-11-16 at 01:05 +0300, Alexey Zaytsev wrote: > >> Just some thoughts. > >> > >> Consider the situation: Files A and B both point to the same inode. > >> File A is being watched, but the user won't get notifications if B is > >> modified. > > > > That's not true. Users watch inodes, not files (this is true for both > > inotify and fanotify). Give it a try, it works. > > > > debian-i386:~/tmp# touch a > debian-i386:~/tmp# ../fanotify a & > debian-i386:~/tmp# link a b > debian-i386:~/tmp# ls -li > total 0 > 3433 -rw-r--r-- 2 root root 0 Nov 15 22:37 a > 3433 -rw-r--r-- 2 root root 0 Nov 15 22:37 b > debian-i386:~/tmp# echo 123 > b > /root/tmp/b: pid=2143 mask = 20 open > /root/tmp/b: pid=2143 mask = a modify 0 - 4 close(writable) 0 - 4 > > Am I doing something wrong? Same thing happens if I watch the mount point. Maybe I don't understand the problem, you watched the inode behind A. You made changes accessing this inode via B, you got notification about those changes. Isn't that what you wanted?