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Cc: freebsd-current@FreeBSD.ORG
Subject: Sloppy uio.uio_procp initialization ...
References: <4.1.19981123122653.00abfe40@206.25.93.69> <19981125142249.B38959@matti.ee> <yzsogpmk1pm.fsf_-_@sicily.odyssey.cs.cmu.edu>
From: "Robert V. Baron" <rvb@cs.cmu.edu>
Date: 07 Dec 1998 22:28:14 -0500
In-Reply-To: "Robert V. Baron"'s message of 02 Dec 1998 10:23:01 -0500
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Recently I fixed vnode_pager_input_old, because it was doing a
VOP_READ into a Coda fs, but it had set the uio.uio_procp to 0 vs
curproc.  (Coda freaks because it vgets a vnode [and hence locks it
with curproc], then tries to unlock it with a 0 process pointer.)
I just noticed (the hard way) the same design happens in ktrwrite():
ktrwrite(vp, kth)
        struct vnode *vp;
        register struct ktr_header *kth;
{
        struct uio auio;
        struct iovec aiov[2];
        register struct proc *p = curproc;      /* XXX */
        int error;

	...
        auio.uio_procp = (struct proc *)0;
	...
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
        error = VOP_WRITE(vp, &auio, IO_UNIT|IO_APPEND, p->p_ucred);
        VOP_UNLOCK(vp, 0, p);

So here the vn_locks are using the actual process pointer, but since
uio_procp is 0, coda will try an unlock not with curproc and fail.  I'll
change ktrwrite to use auio.uio_procp = curproc, Wed Noon EST, unless
anyone objects.

PS
For the curious, Coda is locking and unlocking a vnode associated with
the Coda vnode (which caches the file data) -- not the Coda vnode.

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