linux-kernel - Re: [PATCH 02/10] vfs: check submounts and drop atomically

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Message-ID: <CAJfpegsQ=COW0kGKLmZ_q7t3qTD2TXuFMGL8sSDSOvcRZQU4Gg@mail.gmail.com>
Date:	Thu, 5 Sep 2013 11:11:23 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Ric Wheeler <rwheeler@...hat.com>, Anand Avati <avati@...hat.com>,
	Brian Foster <bfoster@...hat.com>,
	David Howells <dhowells@...hat.com>,
	Eric Paris <eparis@...hat.com>, Ian Kent <raven@...maw.net>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"mszeredi@...e.cz" <mszeredi@...e.cz>,
	Steven Whitehouse <swhiteho@...hat.com>,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 02/10] vfs: check submounts and drop atomically

On Wed, Sep 4, 2013 at 7:58 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Wed, Sep 04, 2013 at 04:05:48PM +0200, Miklos Szeredi wrote:
>
>> +static void check_and_drop(void *_data, struct dentry *dentry)
>> +{
>> +     struct select_data *data = _data;
>> +
>> +     /* We're only interested in the root of this subtree */
>> +     if (data->start == dentry) {
>> +             if (d_mountpoint(dentry))
>> +                     data->found = -EBUSY;
>> +             if (!data->found)
>> +                     __d_drop(dentry);
>> +     }
>> +}
>
> Wouldn't it be better to do that in caller?

It needs to stay under d_lock.  Moving the unlock to caller would be
rather awkward (if we quit walking the start dentry is not even
locked, etc..)  So instead of a ->leave() callback, I just added a
->finish() callback which is called once, when the walk was finished
successfully.

Fixed your other comments too.  I'll do a quick testing and then post
the changed patches.

Thanks,
Miklos
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