Index: sys/fs/pseudofs/pseudofs_vnops.c
===================================================================
--- sys/fs/pseudofs/pseudofs_vnops.c
+++ sys/fs/pseudofs/pseudofs_vnops.c
@@ -68,6 +68,26 @@
 	KASSERT((pn)->pn_type == pfstype_symlink,			\
 	    ("%s(): VLNK vnode refers to non-link pfs_node", __func__))
 
+static int pfs_bufsiz = MAXPHYS;
+
+static int
+sysctl_pfs_bufsiz(SYSCTL_HANDLER_ARGS)
+{
+	int error, limit;
+
+	limit = pfs_bufsiz;
+	error = sysctl_handle_int(oidp, &limit, 0, req);
+	if (error || !req->newptr)
+		return (error);
+	if (limit < 1 || limit > IOSIZE_MAX)
+		return (EINVAL);
+	pfs_bufsiz = limit;
+	return (0);
+}
+SYSCTL_PROC(_vfs_pfs, OID_AUTO, bufsiz, CTLTYPE_INT|CTLFLAG_RW,
+    0, 0, sysctl_pfs_bufsiz, "I",
+    "storage buffer size");
+
 /*
  * Returns the fileno, adjusted for target pid
  */
@@ -663,8 +683,8 @@
 		goto ret;
 	}
 	buflen = uio->uio_offset + uio->uio_resid;
-	if (buflen > MAXPHYS)
-		buflen = MAXPHYS;
+	if (buflen > pfs_bufsiz)
+		buflen = pfs_bufsiz;
 
 	sb = sbuf_new(sb, NULL, buflen + 1, 0);
 	if (sb == NULL) {