linux-kernel - Re: Debugfs : inotify, multiple calls to debugfs_create

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Message-ID: <20061123074727.GA1703@Krystal>
Date:	Thu, 23 Nov 2006 02:47:27 -0500
From:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
To:	Greg KH <greg@...ah.com>
Cc:	ltt-dev@...fik.org, linux-kernel@...r.kernel.org
Subject: Re: Debugfs : inotify, multiple calls to debugfs_create_file, remove

Hi Greg,

Sorry for the delay : I reworked my patches so they fully address the issues.
The patches follows.

Mathieu

* Greg KH (greg@...ah.com) wrote:
> On Mon, Nov 20, 2006 at 01:18:38PM -0500, Mathieu Desnoyers wrote:
> > Hi Greg,
> > 
> > I just had to add inotify support to my LTTng consumer so I could inform it
> > of the presence of new CPUs (for CPU hotplug). I noticed that no
> > notification event was being sent when a debugfs file is created from within
> > the kernel through debugfs_create. There are probably other notifications
> > missing, but here is the patch adding the one I care about. Should it be added
> > in libfs or in debugfs ?
> 
> So does this fix the inotify issue?
> 
> > A second problem I noticed is when a caller calls debugfs_create_file more than
> > once : the result is that the debugfs_remove will fail. I guess the second call
> > to debugfs_create_file increments the reference counts (there is not fix for
> > this issue in my patch).
> > 
> > Third problem : a failing call to debugfs_remove keeps the filesystem pinned.
> > (fixed by calling simple_release_fs in the error path).
> > 
> > The third problem : When a process is in a directory, the call to simple_rmdir
> > will fail. Debugfs does not use its return value. I noticed that calling
> > simple_unlink on a directory when simple_rmdir fails removes the directory that
> > would otherwise be left there. I am not sure if this approach is correct
> > through.
> > 
> > This patch is against Linux 2.6.18.
> 
> Care to split this into 4 different patches (you seem to have 4 issues
> here), so that it's easier to see them, and it will follow the
> 1-patch-per-issue rule?
> 
> thanks,
> 
> greg k-h
> 
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