linux-kernel - Re: [PATCH 03/41] VFS: Make lookup

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Date:	Sun, 29 Nov 2009 21:02:31 -0500
From:	Erez Zadok <ezk@...sunysb.edu>
To:	Valerie Aurora <vaurora@...hat.com>
Cc:	Jan Blunck <jblunck@...e.de>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@...radead.org>,
	Andy Whitcroft <apw@...onical.com>,
	Scott James Remnant <scott@...onical.com>,
	Sandu Popa Marius <sandupopamarius@...il.com>,
	Jan Rekorajski <baggins@...h.mimuw.edu.pl>,
	"J. R. Okajima" <hooanon05@...oo.co.jp>,
	Arnd Bergmann <arnd@...db.de>,
	Vladimir Dronnikov <dronnikov@...il.com>,
	Felix Fietkau <nbd@...nwrt.org>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/41] VFS: Make lookup_hash() return a struct path 

In message <1256152779-10054-4-git-send-email-vaurora@...hat.com>, Valerie Aurora writes:
> From: Jan Blunck <jblunck@...e.de>
> 
> This patch changes lookup_hash() into returning a struct path.

Actually, lookup_hash now also takes a qstr.

This is a somewhat involved patch.  I think more documentation is needed to
list all the places it touches and changes, b/c now struct path has to
propagate in various other places.  (In general, passing struct path instead
of struct dentry is going in the right direction: eventually we could get rid
of lookup_one_len.)

> @@ -1219,14 +1219,22 @@ out:
>   * needs parent already locked. Doesn't follow mounts.
>   * SMP-safe.
>   */
> -static struct dentry *lookup_hash(struct nameidata *nd)
> +static int lookup_hash(struct nameidata *nd, struct qstr *name,
> +		       struct path *path)
>  {

I suggest you document above this function what the @name and @path are for,
who is supposed to allocate and free them, caller/callee's responsibilities,
side effects (if any), new return status upon success/failure, etc.

>  
>  	err = inode_permission(nd->path.dentry->d_inode, MAY_EXEC);
>  	if (err)
> -		return ERR_PTR(err);
> -	return __lookup_hash(&nd->last, nd->path.dentry, nd);
> +		return err;

At least initially, while all this code is being developed, it might also be
a good idea to add

   BUG_ON(!name);
   BUG_ON(!path);

here and possibly in other places which are now taking new pointers.

Erez.
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