linux-kernel - Re: [PATCH 01/34] VFS: Make clone_mnt() and copy

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Message-ID: <20101001015857.GA5003@ram-laptop>
Date:	Thu, 30 Sep 2010 18:58:57 -0700
From:	Ram Pai <linuxram@...ibm.com>
To:	Ram Pai <linuxram@...ibm.com>
Cc:	Valerie Aurora <vaurora@...hat.com>,
	Miklos Szeredi <miklos@...redi.hu>, viro@...iv.linux.org.uk,
	hch@...radead.org, agruen@...e.de, npiggin@...nel.dk,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 01/34] VFS: Make clone_mnt() and copy_tree() return
 error codes

On Thu, Sep 30, 2010 at 05:33:42PM -0700, Ram Pai wrote:
> On Thu, Sep 30, 2010 at 05:44:18PM -0400, Valerie Aurora wrote:
> > (Resend with correct email for Ram Pai)
> > 
> > On Thu, Sep 30, 2010 at 11:51:30AM +0200, Miklos Szeredi wrote:
> > > On Thu, 16 Sep 2010, Valerie Aurora wrote:
> > > > copy_tree() can theoretically fail in a case other than ENOMEM, but
> > > > always returns NULL which is interpreted by callers as -ENOMEM.
> > > > Convert to return an explicit error.  Convert clone_mnt() for
> > > > consistency and because union mounts will add new error cases.
> > > 
> > > I think it makes sense to push this fix to 2.6.37 independently of the
> > > other patches.
> > > 
> > > Acked-by: Miklos Szeredi <mszeredi@...e.cz>
> > 
> > I'm certainly not going to argue, but I spent an hour trying to
> > trigger the non-ENOMEM case (below) and failed - maybe it's
> > unreachable?
> > 
> > > > @@ -1212,11 +1216,12 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
> > > >  	struct path path;
> > > >  
> > > >  	if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
> > > > -		return NULL;
> > > > +		return ERR_PTR(-EINVAL);
> > 
> > Ram, do you remember how this worked?
> 
> Oops. That should be a OR condition. there is one other check in that
> function that should also be a OR condition.

I may be wrong here. Can't exactly recollect what CL_COPY_ALL flag means. Al Viro
might remember?  If CL_COPY_ALL means, to clone everything irrespective of any other
flags, then the above code seems right. 


> 
> BTW: the return value has to be NULL. right? because its not an error
> to clone a unbindable mount. Nor is it an error to not specify CL_COPY_ALL.
> It just means that you want nothing in return.

In any case i think the return value should be NULL.

RP
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