linux-kernel - Re: [PATCH v1 1/2] binderfs: implement "max" mount option

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Message-ID: <20190102111601.gvvxtfw7kg64rczf@brauner.io>
Date:   Wed, 2 Jan 2019 12:16:02 +0100
From:   Christian Brauner <christian@...uner.io>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     gregkh@...uxfoundation.org, tkjos@...roid.com,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        joel@...lfernandes.org, arve@...roid.com, maco@...roid.com,
        Todd Kjos <tkjos@...gle.com>
Subject: Re: [PATCH v1 1/2] binderfs: implement "max" mount option

On Wed, Jan 02, 2019 at 12:17:31PM +0300, Dan Carpenter wrote:
> On Sun, Dec 23, 2018 at 03:35:49PM +0100, Christian Brauner wrote:
> >  static inline struct binderfs_info *BINDERFS_I(const struct inode *inode)
> > @@ -110,10 +132,16 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
> >  
> >  	/* Reserve new minor number for the new device. */
> >  	mutex_lock(&binderfs_minors_mutex);
> > -	minor = ida_alloc_max(&binderfs_minors, BINDERFS_MAX_MINOR, GFP_KERNEL);
> > +	if (++info->device_count <= info->mount_opts.max)
> > +		minor = ida_alloc_max(&binderfs_minors, BINDERFS_MAX_MINOR,
> > +				      GFP_KERNEL);
> > +	else
> > +		minor = -ENOSPC;
> >  	mutex_unlock(&binderfs_minors_mutex);
> > -	if (minor < 0)
> > +	if (minor < 0) {
> > +		--info->device_count;
> 
> Isn't this decrement supposed to happen under binderfs_minors_mutex?

Indeed. Good catch!
Leftover from when this was an atomic_t.

Thanks!
Christian