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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kuyo Chang <kuyo.chang@mediatek.com>,
	major.chen@samsung.com, Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Valentin Schneider <vschneid@redhat.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	wsd_upstream@mediatek.com, hongfei.tang@samsung.com,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org
Subject: Re: [PATCH 1/1] sched/debug: fix dentry leak in update_sched_domain_debugfs
Date: Fri, 2 Sep 2022 16:56:05 +0200	[thread overview]
Message-ID: <YxIZhWB2tCXzlzWj@kroah.com> (raw)
In-Reply-To: <YxIX96nUnwz56fte@ZenIV>

On Fri, Sep 02, 2022 at 03:49:27PM +0100, Al Viro wrote:
> On Fri, Sep 02, 2022 at 11:11:54AM +0200, Greg Kroah-Hartman wrote:
> 
> > +/**
> > + * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
> > + * @name: a pointer to a string containing the name of the item to look up.
> > + * @parent: a pointer to the parent dentry of the item.
> > + *
> > + * This is the equlivant of doing something like
> > + * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
> > + * handled for the directory being looked up.
> > + */
> > +void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
> > +{
> > +	struct dentry *dentry;
> > +
> > +	dentry = debugfs_lookup(name, parent);
> > +	if (IS_ERR_OR_NULL(dentry))
> > +		return;
> 
> 	Could somebody explain how could that return ERR_PTR()?

If debugfs is not enabled then debugfs_lookup() will return an
ERR_PTR().  But, doh, this _IS_ debugfs so you are right, that will
never happen.

> Incidentally, IS_ERR_OR_NULL is almost always a sign of bad interface - or
> that of lazy cargo-culting.  Please, don't propagate that garbage... ;-/

Fair enough, I'll fix that up, many thanks for noticing it.

greg k-h

WARNING: multiple messages have this Message-ID (diff)
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kuyo Chang <kuyo.chang@mediatek.com>,
	major.chen@samsung.com, Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Valentin Schneider <vschneid@redhat.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	wsd_upstream@mediatek.com, hongfei.tang@samsung.com,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org
Subject: Re: [PATCH 1/1] sched/debug: fix dentry leak in update_sched_domain_debugfs
Date: Fri, 2 Sep 2022 16:56:05 +0200	[thread overview]
Message-ID: <YxIZhWB2tCXzlzWj@kroah.com> (raw)
In-Reply-To: <YxIX96nUnwz56fte@ZenIV>

On Fri, Sep 02, 2022 at 03:49:27PM +0100, Al Viro wrote:
> On Fri, Sep 02, 2022 at 11:11:54AM +0200, Greg Kroah-Hartman wrote:
> 
> > +/**
> > + * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
> > + * @name: a pointer to a string containing the name of the item to look up.
> > + * @parent: a pointer to the parent dentry of the item.
> > + *
> > + * This is the equlivant of doing something like
> > + * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
> > + * handled for the directory being looked up.
> > + */
> > +void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
> > +{
> > +	struct dentry *dentry;
> > +
> > +	dentry = debugfs_lookup(name, parent);
> > +	if (IS_ERR_OR_NULL(dentry))
> > +		return;
> 
> 	Could somebody explain how could that return ERR_PTR()?

If debugfs is not enabled then debugfs_lookup() will return an
ERR_PTR().  But, doh, this _IS_ debugfs so you are right, that will
never happen.

> Incidentally, IS_ERR_OR_NULL is almost always a sign of bad interface - or
> that of lazy cargo-culting.  Please, don't propagate that garbage... ;-/

Fair enough, I'll fix that up, many thanks for noticing it.

greg k-h

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linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2022-09-02 15:23 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-02  3:15 [PATCH 1/1] sched/debug: fix dentry leak in update_sched_domain_debugfs Kuyo Chang
2022-09-02  3:15 ` Kuyo Chang
2022-09-02  5:26 ` Greg Kroah-Hartman
2022-09-02  5:26   ` Greg Kroah-Hartman
2022-09-02  6:40   ` Kuyo Chang
2022-09-02  6:40     ` Kuyo Chang
2022-09-02  6:58     ` Greg Kroah-Hartman
2022-09-02  6:58       ` Greg Kroah-Hartman
2022-09-02  7:36       ` Kuyo Chang
2022-09-02  7:36         ` Kuyo Chang
2022-09-02  9:11         ` Greg Kroah-Hartman
2022-09-02  9:11           ` Greg Kroah-Hartman
2022-09-02 10:47           ` Kuyo Chang
2022-09-02 10:47             ` Kuyo Chang
2022-09-02 12:47             ` Greg Kroah-Hartman
2022-09-02 12:47               ` Greg Kroah-Hartman
2022-09-02 14:49           ` Al Viro
2022-09-02 14:49             ` Al Viro
2022-09-02 14:56             ` Greg Kroah-Hartman [this message]
2022-09-02 14:56               ` Greg Kroah-Hartman

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