Refactor the existing machine-dependent sf_buf_free() into a machine-

dependent function by the same name and a machine-independent function,
sf_buf_mext().  Aside from the virtue of making more of the code machine-
independent, this change also makes the interface more logical.  Before,
sf_buf_free() did more than simply undo an sf_buf_alloc(); it also
unwired and if necessary freed the page.  That is now the purpose of
sf_buf_mext().  Thus, sf_buf_alloc() and sf_buf_free() can now be used
as a general-purpose emphemeral map cache.

2 files changed, 25 insertions, 3 deletions

diff --git a/sys/kern/uipc_cow.c b/sys/kern/uipc_cow.c
index ca6b2d8..8c00ffe 100644
--- a/sys/kern/uipc_cow.c
+++ b/sys/kern/uipc_cow.c
@@ -85,7 +85,7 @@ socow_iodone(void *addr, void *args)
 	vm_page_unlock_queues();
 	splx(s);
 	/* note that sf_buf_free() unwires the page for us*/
-	sf_buf_free(addr, args);
+	sf_buf_mext(addr, args);
 	socow_stats.iodone++;
 }
 
diff --git a/sys/kern/uipc_syscalls.c b/sys/kern/uipc_syscalls.c
index 78405a7..9827021 100644
--- a/sys/kern/uipc_syscalls.c
+++ b/sys/kern/uipc_syscalls.c
@@ -1632,6 +1632,28 @@ getsockaddr(namp, uaddr, len)
 }
 
 /*
+ * Detatch mapped page and release resources back to the system.
+ */
+void
+sf_buf_mext(void *addr, void *args)
+{
+	vm_page_t m;
+
+	m = sf_buf_page(args);
+	sf_buf_free(args);
+	vm_page_lock_queues();
+	vm_page_unwire(m, 0);
+	/*
+	 * Check for the object going away on us. This can
+	 * happen since we don't hold a reference to it.
+	 * If so, we're responsible for freeing the page.
+	 */
+	if (m->wire_count == 0 && m->object == NULL)
+		vm_page_free(m);
+	vm_page_unlock_queues();
+}
+
+/*
  * sendfile(2)
  *
  * MPSAFE
@@ -1917,14 +1939,14 @@ retry_lookup:
 			MGETHDR(m, M_TRYWAIT, MT_DATA);
 		if (m == NULL) {
 			error = ENOBUFS;
-			sf_buf_free((void *)sf_buf_kva(sf), sf);
+			sf_buf_mext((void *)sf_buf_kva(sf), sf);
 			sbunlock(&so->so_snd);
 			goto done;
 		}
 		/*
 		 * Setup external storage for mbuf.
 		 */
-		MEXTADD(m, sf_buf_kva(sf), PAGE_SIZE, sf_buf_free, sf, M_RDONLY,
+		MEXTADD(m, sf_buf_kva(sf), PAGE_SIZE, sf_buf_mext, sf, M_RDONLY,
 		    EXT_SFBUF);
 		m->m_data = (char *)sf_buf_kva(sf) + pgoff;
 		m->m_pkthdr.len = m->m_len = xfsize;