From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753390AbaJFTMz (ORCPT ); Mon, 6 Oct 2014 15:12:55 -0400 Received: from mout.gmx.net ([212.227.15.18]:52843 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753011AbaJFTMx (ORCPT ); Mon, 6 Oct 2014 15:12:53 -0400 Message-ID: <5432E921.7040306@gmx.de> Date: Mon, 06 Oct 2014 21:10:25 +0200 From: Heinrich Schuchardt User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.0 MIME-Version: 1.0 To: Jan Kara CC: Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Paris , John McCutchan , Robert Love , Michael Kerrisk Subject: Re: [PATCH 1/1] fallocate: create FAN_MODIFY and IN_MODIFY events References: <1412287587-5392-1-git-send-email-xypron.glpk@gmx.de> <1412324370-959-1-git-send-email-xypron.glpk@gmx.de> <20141006141227.GF7526@quack.suse.cz> In-Reply-To: <20141006141227.GF7526@quack.suse.cz> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V03:K0:TjNRaEmnMozMyCzHXkaJUClFs+ExHLdChH6r+0yK2PKNlGSa1xH uxW3WIHxhgiM/gQ4Lm99ndtEmP7Vq9WardOxFVqTfRWpLdxZfRAL/WTEcf/WRPK7qA2bvi6 zSUMOCT9SJ3Bdg0IF6lRXxyc4STTepY+wYGGqKwHodhgRw7jlDc+rZjADYx3HsQLYQ8NsKw uIpCIprCXllRB2RrZ/qJQ== X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06.10.2014 16:12, Jan Kara wrote: > On Fri 03-10-14 10:19:30, Heinrich Schuchardt wrote: >> The fanotify and the inotify API can used to monitor changes of the file >> system. >> >> System call fallocate modifies files. Hence it should trigger the corresponding >> fanotify (FAN_MODIFY) and inotify (IN_MODIFY) events. >> >> This patch adds the missing call to fsnotify_modify. > Well, there are different fallocate() commands and e.g. pure > FALLOC_FL_KEEP_SIZE call will not change any data in the file. I'm not sure > how much we care but I wanted to point that out... The most interesting case is FALLOC_FL_COLLAPSE_RANGE because this value allows to create arbitrary file content from random data. Hence I think we really need to create FAN_MODIFY in this case. As the fallocate(2) man page teaches: After a successful call, subsequent writes into the range specified by offset and len are guaranteed not to fail because of lack of disk space. So calling fallocate(fd, FALLOC_FL_KEEP_SIZE, offset, len) may result in different outcomes of a subsequent write depending on the values of offset and len. Calling fallocate for a region already zeroed will not result in any data change. I would like to compare fallocate() with write(). When we call write() we always create a FAN_MODIFY event even in the case of overwriting with identical data. So event FAN_MODIFY does not provide any guarantee that data was actually changed. In analogy to write() I suggest to keep the logic for fallocate() as trivial as possible: If fallocate() succeeds, create IN_MODIFY and FAN_MODIFY events. Best regards Heinrich Schuchardt > >> Signed-off-by: Heinrich Schuchardt >> --- >> fs/open.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/fs/open.c b/fs/open.c >> index d6fd3ac..03aa8e5 100644 >> --- a/fs/open.c >> +++ b/fs/open.c >> @@ -295,6 +295,11 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len) >> >> sb_start_write(inode->i_sb); >> ret = file->f_op->fallocate(file, mode, offset, len); >> + >> + /* Create inotify and fanotify events. */ >> + if (ret == 0) >> + fsnotify_modify(file); >> + >> sb_end_write(inode->i_sb); >> return ret; >> } >> -- >> 2.1.0 >>