From owner-cvs-all  Fri Jan 17 17:11:35 2003
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Date: Fri, 17 Jan 2003 17:11:34 -0800 (PST)
From: Nate Lawson <nate@root.org>
To: "Tim J. Robbins" <tjr@FreeBSD.org>
Cc: cvs-all@freebsd.org, cvs-committers@freebsd.org
Subject: Re: cvs commit: src/sys/fs/unionfs union_vfsops.c
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On Fri, 17 Jan 2003, Tim J. Robbins wrote:
>   Modified files:
>     sys/fs/unionfs       union_vfsops.c 
>   Log:
>   Fake up a struct componentname to pass to VOP_WHITEOUT instead of passing
>   NULL. union_whiteout() expects the componentname argument to be non-NULL.
>   Fixes a NULL dereference panic when an existing union mount becomes the
>   upper layer of a new union mount.
> 
> @@ -230,7 +231,15 @@
>  	 * supports whiteout operations.
>  	 */
>  	if ((mp->mnt_flag & MNT_RDONLY) == 0) {
> -		error = VOP_WHITEOUT(um->um_uppervp, NULL, LOOKUP);
> +		/*
> +		 * XXX Fake up a struct componentname with only cn_nameiop
> +		 * and cn_thread valid; union_whiteout() needs to use the
> +		 * thread pointer to lock the vnode.
> +		 */
> +		bzero(&fakecn, sizeof(fakecn));
> +		fakecn.cn_nameiop = LOOKUP;
> +		fakecn.cn_thread = td;
> +		error = VOP_WHITEOUT(um->um_uppervp, &fakecn, LOOKUP);
>  		if (error)
>  			goto bad;
>  	}

Since lookup can sleep, does the vop need to be changed to use curthread
instead of expecting a reference to a thread passed in the struct?

-Nate


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