remove bufq_requeue(), last used by sys/scsi in 2017

diff --git share/man/man9/bufq_init.9 share/man/man9/bufq_init.9
index cc9c5a033bb..7e22116df77 100644
--- share/man/man9/bufq_init.9
+++ share/man/man9/bufq_init.9
@@ -23,7 +23,6 @@
 .Nm bufq_destroy ,
 .Nm bufq_queue ,
 .Nm bufq_dequeue ,
-.Nm bufq_requeue ,
 .Nm bufq_peek ,
 .Nm bufq_drain
 .\" .Nm bufq_wait ,
@@ -43,8 +42,6 @@
 .Fn bufq_queue "struct bufq *bufq" "struct buf *bp"
 .Ft struct buf *
 .Fn bufq_dequeue "struct bufq *bufq"
-.Ft void
-.Fn bufq_requeue "struct bufq *bufq" "struct buf *bp"
 .Ft int
 .Fn bufq_peek "struct bufq *bufq"
 .Ft void
@@ -106,12 +103,6 @@ is used to get the next buf the
 has scheduled to be serviced by a disk.
 The buf will be removed from the queue.
 .Pp
-.Fn bufq_requeue
-can be used to return a previously dequeued buf specified by
-.Fa bp
-to the head of the queue of
-.Fa bufq .
-.Pp
 .Fn bufq_peek
 allows the caller to determine if there are more bufs queued on
 .Fa bufq
@@ -134,7 +125,6 @@ can be called during autoconf, or from process context.
 .Pp
 .Nm bufq_queue ,
 .Nm bufq_dequeue ,
-.Nm bufq_requeue ,
 .Nm bufq_peek ,
 and
 .Nm bufq_drain
diff --git sys/kern/kern_bufq.c sys/kern/kern_bufq.c
index 505770176c4..6bc42e2c874 100644
--- sys/kern/kern_bufq.c
+++ sys/kern/kern_bufq.c
@@ -35,7 +35,6 @@ struct bufq_impl {
 
 	void		 (*impl_queue)(void *, struct buf *);
 	struct buf	*(*impl_dequeue)(void *);
-	void		 (*impl_requeue)(void *, struct buf *);
 	int		 (*impl_peek)(void *);
 };
 
@@ -43,14 +42,12 @@ void		*bufq_fifo_create(void);
 void		 bufq_fifo_destroy(void *);
 void		 bufq_fifo_queue(void *, struct buf *);
 struct buf	*bufq_fifo_dequeue(void *);
-void		 bufq_fifo_requeue(void *, struct buf *);
 int		 bufq_fifo_peek(void *);
 
 void		*bufq_nscan_create(void);
 void		 bufq_nscan_destroy(void *);
 void		 bufq_nscan_queue(void *, struct buf *);
 struct buf	*bufq_nscan_dequeue(void *);
-void		 bufq_nscan_requeue(void *, struct buf *);
 int		 bufq_nscan_peek(void *);
 
 const struct bufq_impl bufq_impls[BUFQ_HOWMANY] = {
@@ -59,7 +56,6 @@ const struct bufq_impl bufq_impls[BUFQ_HOWMANY] = {
 		bufq_fifo_destroy,
 		bufq_fifo_queue,
 		bufq_fifo_dequeue,
-		bufq_fifo_requeue,
 		bufq_fifo_peek
 	},
 	{
@@ -67,7 +63,6 @@ const struct bufq_impl bufq_impls[BUFQ_HOWMANY] = {
 		bufq_nscan_destroy,
 		bufq_nscan_queue,
 		bufq_nscan_dequeue,
-		bufq_nscan_requeue,
 		bufq_nscan_peek
 	}
 };
@@ -201,14 +196,6 @@ bufq_dequeue(struct bufq *bq)
 	return (bp);
 }
 
-void
-bufq_requeue(struct bufq *bq, struct buf *bp)
-{
-	mtx_enter(&bq->bufq_mtx);
-	bq->bufq_impl->impl_requeue(bq->bufq_data, bp);
-	mtx_leave(&bq->bufq_mtx);
-}
-
 int
 bufq_peek(struct bufq *bq)
 {
@@ -354,14 +341,6 @@ bufq_fifo_dequeue(void *data)
 	return (bp);
 }
 
-void
-bufq_fifo_requeue(void *data, struct buf *bp)
-{
-	struct bufq_fifo_head	*head = data;
-
-	SIMPLEQ_INSERT_HEAD(head, bp, b_bufq.bufq_data_fifo.bqf_entries);
-}
-
 int
 bufq_fifo_peek(void *data)
 {
@@ -491,14 +470,6 @@ bufq_nscan_dequeue(void *vdata)
 	return (bp);
 }
 
-void
-bufq_nscan_requeue(void *vdata, struct buf *bp)
-{
-	struct bufq_nscan_data *data = vdata;
-
-	SIMPLEQ_INSERT_HEAD(&data->fifo, bp, dsentries);
-}
-
 int
 bufq_nscan_peek(void *vdata)
 {
diff --git sys/sys/buf.h sys/sys/buf.h
index d123377383f..c7feb84cab1 100644
--- sys/sys/buf.h
+++ sys/sys/buf.h
@@ -89,7 +89,6 @@ void		 bufq_destroy(struct bufq *);
 
 void		 bufq_queue(struct bufq *, struct buf *);
 struct buf	*bufq_dequeue(struct bufq *);
-void		 bufq_requeue(struct bufq *, struct buf *);
 int		 bufq_peek(struct bufq *);
 void		 bufq_drain(struct bufq *);