--- Add new FOREACH_FROM variants of the queue(3) FOREACH macros which can
--- optionally start the traversal from a previously found element by passing
--- the element in as "var". Passing a NULL "var" retains the same semantics as
--- the regular FOREACH macros.
---
--- Reviewed by:	?
--- MFC after:		1 week
---
Index: sys/sys/queue.h
===================================================================
--- sys/sys/queue.h	(revision 250136)
+++ sys/sys/queue.h	(working copy)
@@ -88,8 +88,10 @@
  * _PREV			-	+	-	+
  * _LAST			-	-	+	+
  * _FOREACH			+	+	+	+
+ * _FOREACH_FROM		+	+	+	+
  * _FOREACH_SAFE		+	+	+	+
  * _FOREACH_REVERSE		-	-	-	+
+ * _FOREACH_REVERSE_FROM	-	-	-	+
  * _FOREACH_REVERSE_SAFE	-	-	-	+
  * _INSERT_HEAD			+	+	+	+
  * _INSERT_BEFORE		-	+	-	+
@@ -167,6 +169,11 @@
 	    (var);							\
 	    (var) = SLIST_NEXT((var), field))
 
+#define	SLIST_FOREACH_FROM(var, head, field)				\
+	for ((var) = ((var) ? (var) : SLIST_FIRST((head)));		\
+	    (var);							\
+	    (var) = SLIST_NEXT((var), field))
+
 #define	SLIST_FOREACH_SAFE(var, head, field, tvar)			\
 	for ((var) = SLIST_FIRST((head));				\
 	    (var) && ((tvar) = SLIST_NEXT((var), field), 1);		\
@@ -259,6 +266,10 @@
 	   (var);							\
 	   (var) = STAILQ_NEXT((var), field))
 
+#define	STAILQ_FOREACH_FROM(var, head, field)				\
+	for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));		\
+	   (var);							\
+	   (var) = STAILQ_NEXT((var), field))
 
 #define	STAILQ_FOREACH_SAFE(var, head, field, tvar)			\
 	for ((var) = STAILQ_FIRST((head));				\
@@ -389,6 +400,11 @@
 	    (var);							\
 	    (var) = LIST_NEXT((var), field))
 
+#define	LIST_FOREACH_FROM(var, head, field)				\
+	for ((var) = ((var) ? (var) : LIST_FIRST((head)));		\
+	    (var);							\
+	    (var) = LIST_NEXT((var), field))
+
 #define	LIST_FOREACH_SAFE(var, head, field, tvar)			\
 	for ((var) = LIST_FIRST((head));				\
 	    (var) && ((tvar) = LIST_NEXT((var), field), 1);		\
@@ -526,6 +542,11 @@
 	    (var);							\
 	    (var) = TAILQ_NEXT((var), field))
 
+#define	TAILQ_FOREACH_FROM(var, head, field)				\
+	for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));		\
+	    (var);							\
+	    (var) = TAILQ_NEXT((var), field))
+
 #define	TAILQ_FOREACH_SAFE(var, head, field, tvar)			\
 	for ((var) = TAILQ_FIRST((head));				\
 	    (var) && ((tvar) = TAILQ_NEXT((var), field), 1);		\
@@ -536,6 +557,11 @@
 	    (var);							\
 	    (var) = TAILQ_PREV((var), headname, field))
 
+#define	TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field)		\
+	for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));	\
+	    (var);							\
+	    (var) = TAILQ_PREV((var), headname, field))
+
 #define	TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)	\
 	for ((var) = TAILQ_LAST((head), headname);			\
 	    (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);	\
Index: share/man/man3/queue.3
===================================================================
--- share/man/man3/queue.3	(revision 250136)
+++ share/man/man3/queue.3	(working copy)
@@ -32,7 +32,7 @@
 .\"	@(#)queue.3	8.2 (Berkeley) 1/24/94
 .\" $FreeBSD$
 .\"
-.Dd Sep 12, 2012
+.Dd May 1, 2013
 .Dt QUEUE 3
 .Os
 .Sh NAME
@@ -40,6 +40,7 @@
 .Nm SLIST_ENTRY ,
 .Nm SLIST_FIRST ,
 .Nm SLIST_FOREACH ,
+.Nm SLIST_FOREACH_FROM ,
 .Nm SLIST_FOREACH_SAFE ,
 .Nm SLIST_HEAD ,
 .Nm SLIST_HEAD_INITIALIZER ,
@@ -56,6 +57,7 @@
 .Nm STAILQ_ENTRY ,
 .Nm STAILQ_FIRST ,
 .Nm STAILQ_FOREACH ,
+.Nm STAILQ_FOREACH_FROM ,
 .Nm STAILQ_FOREACH_SAFE ,
 .Nm STAILQ_HEAD ,
 .Nm STAILQ_HEAD_INITIALIZER ,
@@ -73,6 +75,7 @@
 .Nm LIST_ENTRY ,
 .Nm LIST_FIRST ,
 .Nm LIST_FOREACH ,
+.Nm LIST_FOREACH_FROM ,
 .Nm LIST_FOREACH_SAFE ,
 .Nm LIST_HEAD ,
 .Nm LIST_HEAD_INITIALIZER ,
@@ -89,8 +92,10 @@
 .Nm TAILQ_ENTRY ,
 .Nm TAILQ_FIRST ,
 .Nm TAILQ_FOREACH ,
+.Nm TAILQ_FOREACH_FROM ,
 .Nm TAILQ_FOREACH_SAFE ,
 .Nm TAILQ_FOREACH_REVERSE ,
+.Nm TAILQ_FOREACH_REVERSE_FROM ,
 .Nm TAILQ_FOREACH_REVERSE_SAFE ,
 .Nm TAILQ_HEAD ,
 .Nm TAILQ_HEAD_INITIALIZER ,
@@ -113,6 +118,7 @@
 .Fn SLIST_ENTRY "TYPE"
 .Fn SLIST_FIRST "SLIST_HEAD *head"
 .Fn SLIST_FOREACH "TYPE *var" "SLIST_HEAD *head" "SLIST_ENTRY NAME"
+.Fn SLIST_FOREACH_FROM "TYPE *var" "SLIST_HEAD *head" "SLIST_ENTRY NAME"
 .Fn SLIST_FOREACH_SAFE "TYPE *var" "SLIST_HEAD *head" "SLIST_ENTRY NAME" "TYPE *temp_var"
 .Fn SLIST_HEAD "HEADNAME" "TYPE"
 .Fn SLIST_HEAD_INITIALIZER "SLIST_HEAD head"
@@ -130,6 +136,7 @@
 .Fn STAILQ_ENTRY "TYPE"
 .Fn STAILQ_FIRST "STAILQ_HEAD *head"
 .Fn STAILQ_FOREACH "TYPE *var" "STAILQ_HEAD *head" "STAILQ_ENTRY NAME"
+.Fn STAILQ_FOREACH_FROM "TYPE *var" "STAILQ_HEAD *head" "STAILQ_ENTRY NAME"
 .Fn STAILQ_FOREACH_SAFE "TYPE *var" "STAILQ_HEAD *head" "STAILQ_ENTRY NAME" "TYPE *temp_var"
 .Fn STAILQ_HEAD "HEADNAME" "TYPE"
 .Fn STAILQ_HEAD_INITIALIZER "STAILQ_HEAD head"
@@ -148,6 +155,7 @@
 .Fn LIST_ENTRY "TYPE"
 .Fn LIST_FIRST "LIST_HEAD *head"
 .Fn LIST_FOREACH "TYPE *var" "LIST_HEAD *head" "LIST_ENTRY NAME"
+.Fn LIST_FOREACH_FROM "TYPE *var" "LIST_HEAD *head" "LIST_ENTRY NAME"
 .Fn LIST_FOREACH_SAFE "TYPE *var" "LIST_HEAD *head" "LIST_ENTRY NAME" "TYPE *temp_var"
 .Fn LIST_HEAD "HEADNAME" "TYPE"
 .Fn LIST_HEAD_INITIALIZER "LIST_HEAD head"
@@ -165,8 +173,10 @@
 .Fn TAILQ_ENTRY "TYPE"
 .Fn TAILQ_FIRST "TAILQ_HEAD *head"
 .Fn TAILQ_FOREACH "TYPE *var" "TAILQ_HEAD *head" "TAILQ_ENTRY NAME"
+.Fn TAILQ_FOREACH_FROM "TYPE *var" "TAILQ_HEAD *head" "TAILQ_ENTRY NAME"
 .Fn TAILQ_FOREACH_SAFE "TYPE *var" "TAILQ_HEAD *head" "TAILQ_ENTRY NAME" "TYPE *temp_var"
 .Fn TAILQ_FOREACH_REVERSE "TYPE *var" "TAILQ_HEAD *head" "HEADNAME" "TAILQ_ENTRY NAME"
+.Fn TAILQ_FOREACH_REVERSE_FROM "TYPE *var" "TAILQ_HEAD *head" "HEADNAME" "TAILQ_ENTRY NAME"
 .Fn TAILQ_FOREACH_REVERSE_SAFE "TYPE *var" "TAILQ_HEAD *head" "HEADNAME" "TAILQ_ENTRY NAME" "TYPE *temp_var"
 .Fn TAILQ_HEAD "HEADNAME" "TYPE"
 .Fn TAILQ_HEAD_INITIALIZER "TAILQ_HEAD head"
@@ -365,6 +375,19 @@
 .Fa var .
 .Pp
 The macro
+.Nm SLIST_FOREACH_FROM
+behaves identically to
+.Nm SLIST_FOREACH
+when
+.Fa var
+is NULL, else it treats
+.Fa var
+as a previously found slist element and begins the loop at
+.Fa var
+instead of the first element in the slist referenced by
+.Fa head .
+.Pp
+The macro
 .Nm SLIST_FOREACH_SAFE
 traverses the list referenced by
 .Fa head
@@ -544,6 +567,19 @@
 .Fa var .
 .Pp
 The macro
+.Nm STAILQ_FOREACH_FROM
+behaves identically to
+.Nm STAILQ_FOREACH
+when
+.Fa var
+is NULL, else it treats
+.Fa var
+as a previously found stailq element and begins the loop at
+.Fa var
+instead of the first element in the stailq referenced by
+.Fa head .
+.Pp
+The macro
 .Nm STAILQ_FOREACH_SAFE
 traverses the tail queue referenced by
 .Fa head
@@ -733,6 +769,19 @@
 .Fa var .
 .Pp
 The macro
+.Nm LIST_FOREACH_FROM
+behaves identically to
+.Nm LIST_FOREACH
+when
+.Fa var
+is NULL, else it treats
+.Fa var
+as a previously found list element and begins the loop at
+.Fa var
+instead of the first element in the list referenced by
+.Fa head .
+.Pp
+The macro
 .Nm LIST_FOREACH_SAFE
 traverses the list referenced by
 .Fa head
@@ -918,12 +967,38 @@
 if the loop completes normally, or if there were no elements.
 .Pp
 The macro
+.Nm TAILQ_FOREACH_FROM
+behaves identically to
+.Nm TAILQ_FOREACH
+when
+.Fa var
+is NULL, else it treats
+.Fa var
+as a previously found tailq element and begins the loop at
+.Fa var
+instead of the first element in the tailq referenced by
+.Fa head .
+.Pp
+The macro
 .Nm TAILQ_FOREACH_REVERSE
 traverses the tail queue referenced by
 .Fa head
 in the reverse direction, assigning each element in turn to
 .Fa var .
 .Pp
+The macro
+.Nm TAILQ_FOREACH_REVERSE_FROM
+behaves identically to
+.Nm TAILQ_FOREACH_REVERSE
+when
+.Fa var
+is NULL, else it treats
+.Fa var
+as a previously found tailq element and begins the reverse loop at
+.Fa var
+instead of the last element in the tailq referenced by
+.Fa head .
+.Pp
 The macros
 .Nm TAILQ_FOREACH_SAFE
 and