From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heinrich Schuchardt Subject: Re: [PATCH 1/1] ftruncate: create FAN_MODIFY and IN_MODIFY events Date: Mon, 06 Oct 2014 22:09:12 +0200 Message-ID: <5432F6E8.7010607@gmx.de> References: <1412360190-1507-1-git-send-email-xypron.glpk@gmx.de> <20141006132449.GD7526@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Paris , Michael Kerrisk , John McCutchan , Robert Love To: Jan Kara Return-path: Received: from mout.gmx.net ([212.227.17.20]:64275 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750720AbaJFULq (ORCPT ); Mon, 6 Oct 2014 16:11:46 -0400 In-Reply-To: <20141006132449.GD7526@quack.suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 06.10.2014 15:24, Jan Kara wrote: > On Fri 03-10-14 20:16:30, Heinrich Schuchardt wrote: >> The fanotify and the inotify API can be used to monitor changes of the file >> system. >> >> System call ftruncate modifies files. Hence it should trigger the corresponding >> fanotify (FAN_MODIFY) and inotify (IN_MODIFY) events. > Hum, I would think that the appropriate event gets generated by > fsnotify_change() called from notify_change()? > > Honza Hello Jan, thank you for reviewing. fsnotify_change() calls fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE, NULL, 0); fsnotify_modify() calls fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0); Only with FSNOTIFY_EVENT_PATH a mount is determined in fsnotify(). So a FAN_MODIFY event for a mount cannot occur. But I also did not see a FAN_MODIFY event when watching a file either. IN_MODIFY events are actually created. So would it be better to do the change in do_truncate and replace the call to notify_change by a call to fsnotify_modify? I just had a look at http://lxr.free-electrons.com/ident?i=notify_change There seem to be some other usages of notify_change that deserve consideration, e.g. in ecryptfs_truncate(). Best regards Heinrich Schuchardt >> >> Signed-off-by: Heinrich Schuchardt >> --- >> fs/open.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/fs/open.c b/fs/open.c >> index d6fd3ac..e36f26e 100644 >> --- a/fs/open.c >> +++ b/fs/open.c >> @@ -189,6 +189,8 @@ static long do_sys_ftruncate(unsigned int fd, loff_t length, int small) >> error = security_path_truncate(&f.file->f_path); >> if (!error) >> error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file); >> + if (!error) >> + fsnotify_modify(f.file); >> sb_end_write(inode->i_sb); >> out_putf: >> fdput(f); >> -- >> 2.1.0 >>