Change the kernel's ucred API as follows:

- crhold() returns a reference to the ucred whose refcount it bumps.
- crcopy() now simply copies the credentials from one credential to
  another and has no return value.
- a new crshared() primitive is added which returns true if a ucred's
  refcount is > 1 and false (0) otherwise.

2 files changed, 14 insertions, 21 deletions

diff --git a/sys/vm/swap_pager.c b/sys/vm/swap_pager.c
index e25a556..711a00f 100644
--- a/sys/vm/swap_pager.c
+++ b/sys/vm/swap_pager.c
@@ -1134,10 +1134,9 @@ swap_pager_getpages(object, m, count, reqpage)
 
 	bp->b_iocmd = BIO_READ;
 	bp->b_iodone = swp_pager_async_iodone;
-	bp->b_rcred = bp->b_wcred = proc0.p_ucred;
+	bp->b_rcred = crhold(proc0.p_ucred);
+	bp->b_wcred = crhold(proc0.p_ucred);
 	bp->b_data = (caddr_t) kva;
-	crhold(bp->b_rcred);
-	crhold(bp->b_wcred);
 	bp->b_blkno = blk - (reqpage - i);
 	bp->b_bcount = PAGE_SIZE * (j - i);
 	bp->b_bufsize = PAGE_SIZE * (j - i);
@@ -1386,14 +1385,12 @@ swap_pager_putpages(object, m, count, sync, rtvals)
 
 		pmap_qenter((vm_offset_t)bp->b_data, &m[i], n);
 
-		bp->b_rcred = bp->b_wcred = proc0.p_ucred;
+		bp->b_rcred = crhold(proc0.p_ucred);
+		bp->b_wcred = crhold(proc0.p_ucred);
 		bp->b_bcount = PAGE_SIZE * n;
 		bp->b_bufsize = PAGE_SIZE * n;
 		bp->b_blkno = blk;
 
-		crhold(bp->b_rcred);
-		crhold(bp->b_wcred);
-
 		pbgetvp(swapdev_vp, bp);
 
 		for (j = 0; j < n; ++j) {
@@ -2082,12 +2079,10 @@ getchainbuf(struct bio *bp, struct vnode *vp, int flags)
 	nbp->b_iocmd = bp->bio_cmd;
 	nbp->b_ioflags = bp->bio_flags & BIO_ORDERED;
 	nbp->b_flags = flags;
-	nbp->b_rcred = nbp->b_wcred = proc0.p_ucred;
+	nbp->b_rcred = crhold(proc0.p_ucred);
+	nbp->b_wcred = crhold(proc0.p_ucred);
 	nbp->b_iodone = vm_pager_chain_iodone;
 
-	crhold(nbp->b_rcred);
-	crhold(nbp->b_wcred);
-
 	if (vp)
 		pbgetvp(vp, nbp);
 	return(nbp);
diff --git a/sys/vm/vnode_pager.c b/sys/vm/vnode_pager.c
index bad9bcf..97e7039 100644
--- a/sys/vm/vnode_pager.c
+++ b/sys/vm/vnode_pager.c
@@ -434,11 +434,10 @@ vnode_pager_input_smlfs(object, m)
 			/* build a minimal buffer header */
 			bp->b_iocmd = BIO_READ;
 			bp->b_iodone = vnode_pager_iodone;
-			bp->b_rcred = bp->b_wcred = curthread->td_proc->p_ucred;
-			if (bp->b_rcred != NOCRED)
-				crhold(bp->b_rcred);
-			if (bp->b_wcred != NOCRED)
-				crhold(bp->b_wcred);
+			KASSERT(bp->b_rcred == NOCRED, ("leaking read ucred"));
+			KASSERT(bp->b_wcred == NOCRED, ("leaking write ucred"));
+			bp->b_rcred = crhold(curthread->td_proc->p_ucred);
+			bp->b_wcred = crhold(curthread->td_proc->p_ucred);
 			bp->b_data = (caddr_t) kva + i * bsize;
 			bp->b_blkno = fileaddr;
 			pbgetvp(dp, bp);
@@ -754,11 +753,10 @@ vnode_pager_generic_getpages(vp, m, bytecount, reqpage)
 	bp->b_iocmd = BIO_READ;
 	bp->b_iodone = vnode_pager_iodone;
 	/* B_PHYS is not set, but it is nice to fill this in */
-	bp->b_rcred = bp->b_wcred = curthread->td_proc->p_ucred;
-	if (bp->b_rcred != NOCRED)
-		crhold(bp->b_rcred);
-	if (bp->b_wcred != NOCRED)
-		crhold(bp->b_wcred);
+	KASSERT(bp->b_rcred == NOCRED, ("leaking read ucred"));
+	KASSERT(bp->b_wcred == NOCRED, ("leaking write ucred"));
+	bp->b_rcred = crhold(curthread->td_proc->p_ucred);
+	bp->b_wcred = crhold(curthread->td_proc->p_ucred);
 	bp->b_blkno = firstaddr;
 	pbgetvp(dp, bp);
 	bp->b_bcount = size;