svn commit: r348701 - head/sys/vm

[Konstantin Belousov]

Author: kib
Date: Wed Jun  5 20:21:17 2019
New Revision: 348701
URL: https://svnweb.freebsd.org/changeset/base/348701

Log:
  In vm_map_entry_set_vnode_text(), tolerate tmpfs mappings for which
  vnode is no longer resident.
  
  Mapping of tmpfs file does not bump use count on the vnode, because
  backing object has swap type.  As result, even during normal
  operations, and of course on forced unmount, we might end up with text
  mapping from tmpfs node which has no vnode in memory.  In this case,
  there is no v_writecount to clear (this was done during reclaim), and
  no reason to assert that the vnode is present.
  
  Restructure the code to silently ignore OBJ_SWAP objects with
  OBJ_TMPFS_NODE flag set, but OBJ_TMPFS flag clear.
  
  Reported and tested by:	pho
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/sys/vm/vm_map.c

Modified: head/sys/vm/vm_map.c
==============================================================================
--- head/sys/vm/vm_map.c	Wed Jun  5 20:18:56 2019	(r348700)
+++ head/sys/vm/vm_map.c	Wed Jun  5 20:21:17 2019	(r348701)
@@ -526,19 +526,31 @@ vm_map_entry_set_vnode_text(vm_map_entry_t entry, bool
 		object = object1;
 	}
 
-	/*
-	 * For OBJT_DEAD objects, v_writecount was handled in
-	 * vnode_pager_dealloc().
-	 */
-	if (object->type != OBJT_DEAD) {
-		KASSERT(((object->flags & OBJ_TMPFS) == 0 &&
-		    object->type == OBJT_VNODE) ||
-		    ((object->flags & OBJ_TMPFS) != 0 &&
-		    object->type == OBJT_SWAP),
+	vp = NULL;
+	if (object->type == OBJT_DEAD) {
+		/*
+		 * For OBJT_DEAD objects, v_writecount was handled in
+		 * vnode_pager_dealloc().
+		 */
+	} else if (object->type == OBJT_VNODE) {
+		vp = object->handle;
+	} else if (object->type == OBJT_SWAP) {
+		KASSERT((object->flags & OBJ_TMPFS_NODE) != 0,
+		    ("vm_map_entry_set_vnode_text: swap and !TMPFS "
+		    "entry %p, object %p, add %d", entry, object, add));
+		/*
+		 * Tmpfs VREG node, which was reclaimed, has
+		 * OBJ_TMPFS_NODE flag set, but not OBJ_TMPFS.  In
+		 * this case there is no v_writecount to adjust.
+		 */
+		if ((object->flags & OBJ_TMPFS) != 0)
+			vp = object->un_pager.swp.swp_tmpfs;
+	} else {
+		KASSERT(0,
 		    ("vm_map_entry_set_vnode_text: wrong object type, "
 		    "entry %p, object %p, add %d", entry, object, add));
-		vp = (object->flags & OBJ_TMPFS) == 0 ? object->handle :
-		    object->un_pager.swp.swp_tmpfs;
+	}
+	if (vp != NULL) {
 		if (add)
 			VOP_SET_TEXT_CHECKED(vp);
 		else