linux-kernel - Re: [PATCH v2 1/2] binder: Add default binder devices through binderfs when configured

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Message-ID: <20190807174937.53qo7uninqi3c6xq@brauner.io>
Date:   Wed, 7 Aug 2019 19:50:06 +0200
From:   Christian Brauner <christian@...uner.io>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Hridya Valsaraju <hridya@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Christian Brauner <christian@...uner.io>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        Christian Brauner <christian.brauner@...ntu.com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v2 1/2] binder: Add default binder devices through
 binderfs when configured

On Wed, Aug 07, 2019 at 02:02:05PM +0300, Dan Carpenter wrote:
> On Tue, Aug 06, 2019 at 11:40:05AM -0700, Hridya Valsaraju wrote:
> > @@ -467,6 +466,9 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
> >  	int ret;
> >  	struct binderfs_info *info;
> >  	struct inode *inode = NULL;
> > +	struct binderfs_device device_info = { 0 };
> > +	const char *name;
> > +	size_t len;
> >  
> >  	sb->s_blocksize = PAGE_SIZE;
> >  	sb->s_blocksize_bits = PAGE_SHIFT;
> > @@ -521,7 +523,24 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
> >  	if (!sb->s_root)
> >  		return -ENOMEM;
> >  
> > -	return binderfs_binder_ctl_create(sb);
> > +	ret = binderfs_binder_ctl_create(sb);
> > +	if (ret)
> > +		return ret;
> > +
> > +	name = binder_devices_param;
> > +	for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {
> > +		strscpy(device_info.name, name, len + 1);
> > +		ret = binderfs_binder_device_create(inode, NULL, &device_info);
> > +		if (ret)
> > +			return ret;
> 
> We should probably clean up before returning...  The error handling code
> would probably be tricky to write though and it's not super common.

struct dentry *mount_nodev(struct file_system_type *fs_type,
	int flags, void *data,
	int (*fill_super)(struct super_block *, void *, int))
{
	<snip>

	error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
	if (error) {
		deactivate_locked_super(s);
		return ERR_PTR(error);
	}

	<snip>
}

	deactivate_locked_super()
will call
	fs->kill_sb(s)
which calls
	binderfs_kill_super()
which calls
	kill_litter_super()
the latter will destory any remaining dentries and then calls
	generic_shutdown_super()
which calls
	evict_inodes()
which calls
	evict(inode)
which calls the binderfs specific
	binderfs_evict_inode()
and get rid of the rest.

So manually cleaning up is not needed, imho.

Christian