linux-kernel - Re: missing mnt_drop

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Message-ID: <20070926150745.GB24744@infradead.org>
Date:	Wed, 26 Sep 2007 16:07:45 +0100
From:	Christoph Hellwig <hch@...radead.org>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	haveblue@...ibm.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: missing mnt_drop_write() on open error

On Wed, Sep 26, 2007 at 10:38:22AM +0200, Miklos Szeredi wrote:
> Also even more horrible things can happen because of the
> nd->intent.open.file thing.  For example if the lookup routine calls
> lookup_instantiate_filp(), and after this, but before may_open() some
> error happens, then release_open_intent() will call fput() on the
> file, which will cause mnt_drop_write() to be called, even though a
> matching mnt_want_write() hasn't yet been called.  Ugly, eh?

It's more than horrible.  I wouldn't mind using the word utter crap
for it.  It's defintively on my todo list to get rid of this junk
again.  It managed to get in without proper review unfortunately.

> 
> > I'm also thinking that we should change the open_namei*
> > functions to simply return 'struct file *'.  Those are the only users
> > other than NFS, and forcing the return of a file like that will force
> > users to do the fput() on it if they don't want it any more.  We'd just
> > need to make sure no new may_open() users pop up.  Any thoughts on that?
> 
> Yeah, something needs to be done with open, because currently it's way
> too convoluted.

I have some changes for open_namei pending and I'll see if incorporating
this makes sense.
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