Index: sys/kern/vfs_vnops.c
===================================================================
--- sys/kern/vfs_vnops.c
+++ sys/kern/vfs_vnops.c
@@ -184,6 +184,22 @@
 	} args;
 };
 
+/*
+ * Structure used to pass arguments to vn_deallocate_impl(), to do either
+ * file- or vnode-based I/O calls.
+ */
+struct vn_deallocate_args {
+	enum {
+		VN_DEALLOCATE_FOP,
+		VN_DEALLOCATE_VOP
+	} kind;
+	struct vnode *vp;
+	struct ucred *active_cred;
+	struct ucred *file_cred;
+	int flags;
+	int ioflag;
+};
+
 static int vn_io_fault1(struct vnode *vp, struct uio *uio,
     struct vn_io_fault_args *args, struct thread *td);
 
@@ -3462,9 +3478,10 @@
 }
 
 static int
-vn_deallocate_impl(struct vnode *vp, off_t *offset, off_t *length, int flags,
-    int ioflag, struct ucred *active_cred, struct ucred *file_cred)
+vn_deallocate_impl(struct vn_deallocate_args *args, off_t *offset,
+    off_t *length)
 {
+	struct ucred *cred;
 	struct mount *mp;
 	void *rl_cookie;
 	off_t off, len;
@@ -3472,14 +3489,16 @@
 #ifdef AUDIT
 	bool audited_vnode1 = false;
 #endif
+	struct vnode *vp;
 
 	rl_cookie = NULL;
 	error = 0;
 	mp = NULL;
 	off = *offset;
 	len = *length;
+	vp = args->vp;
 
-	if ((ioflag & (IO_NODELOCKED | IO_RANGELOCKED)) == 0)
+	if ((args->ioflag & (IO_NODELOCKED | IO_RANGELOCKED)) == 0)
 		rl_cookie = vn_rangelock_wlock(vp, off, off + len);
 	while (len > 0 && error == 0) {
 		/*
@@ -3489,7 +3508,7 @@
 		 * pass.
 		 */
 
-		if ((ioflag & IO_NODELOCKED) == 0) {
+		if ((args->ioflag & IO_NODELOCKED) == 0) {
 			bwillwrite();
 			if ((error = vn_start_write(vp, &mp,
 			    V_WAIT | PCATCH)) != 0)
@@ -3504,15 +3523,21 @@
 #endif
 
 #ifdef MAC
-		if ((ioflag & IO_NOMACCHECK) == 0)
-			error = mac_vnode_check_write(active_cred, file_cred,
-			    vp);
+		if ((args->ioflag & IO_NOMACCHECK) == 0)
+			error = mac_vnode_check_write(args->active_cred,
+			    args->file_cred, vp);
 #endif
-		if (error == 0)
-			error = VOP_DEALLOCATE(vp, &off, &len, flags, ioflag,
-			    active_cred);
+		if (error == 0) {
+			if (args->kind == VN_DEALLOCATE_VOP &&
+			    args->file_cred != NULL)
+				cred = args->file_cred;
+			else
+				cred = args->active_cred;
+			error = VOP_DEALLOCATE(vp, &off, &len, args->flags,
+			    args->ioflag, cred);
+		}
 
-		if ((ioflag & IO_NODELOCKED) == 0) {
+		if ((args->ioflag & IO_NODELOCKED) == 0) {
 			VOP_UNLOCK(vp);
 			if (mp != NULL) {
 				vn_finished_write(mp);
@@ -3530,27 +3555,38 @@
 	return (error);
 }
 
+/*
+ * If file_cred is non-NULL, it is chosen over active_cred.
+ */
 int
 vn_deallocate(struct vnode *vp, off_t *offset, off_t *length, int flags,
     int ioflag, struct ucred *active_cred, struct ucred *file_cred)
 {
+	struct vn_deallocate_args args;
+
 	if (*offset < 0 || *length <= 0 || *length > OFF_MAX - *offset ||
 	    flags != 0)
 		return (EINVAL);
 	if (vp->v_type != VREG)
 		return (ENODEV);
 
-	return (vn_deallocate_impl(vp, offset, length, flags, ioflag,
-	    active_cred, file_cred));
+	args.vp = vp;
+	args.kind = VN_DEALLOCATE_VOP;
+	args.active_cred = active_cred;
+	args.file_cred = file_cred;
+	args.flags = flags;
+	args.ioflag = ioflag;
+	return (vn_deallocate_impl(&args, offset, length));
 }
 
 static int
 vn_fspacectl(struct file *fp, int cmd, off_t *offset, off_t *length, int flags,
     struct ucred *active_cred, struct thread *td)
 {
-	int error;
+	struct vn_deallocate_args args;
 	struct vnode *vp;
 	int ioflag;
+	int error;
 
 	vp = fp->f_vnode;
 
@@ -3564,8 +3600,13 @@
 
 	switch (cmd) {
 	case SPACECTL_DEALLOC:
-		error = vn_deallocate_impl(vp, offset, length, flags, ioflag,
-		    active_cred, fp->f_cred);
+		args.vp = vp;
+		args.kind = VN_DEALLOCATE_FOP;
+		args.active_cred = active_cred;
+		args.file_cred = fp->f_cred;
+		args.flags = flags;
+		args.ioflag = ioflag;
+		error = vn_deallocate_impl(&args, offset, length);
 		break;
 	default:
 		panic("vn_fspacectl: unknown cmd %d", cmd);