From 333dcaa4981d495bc1606a3bdf7445be56a451d5 Mon Sep 17 00:00:00 2001
From: Matt Joras <mjoras@FreeBSD.org>
Date: Wed, 11 Oct 2017 21:53:50 +0000
Subject: [PATCH] Add clearing function for unr(9).

Previously before you could call unrhdr_delete you needed to
individually free every allocated unit. It is useful to be able to tear
down the unr without having to go through this process, as it is
significantly faster than freeing the individual units.

Reviewed by:	cem, lidl
Approved by:	rstone (mentor)
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D12591
---
 share/man/man9/Makefile |  1 +
 share/man/man9/unr.9    | 15 +++++++++++++--
 sys/kern/subr_unit.c    | 21 +++++++++++++++++++++
 sys/sys/systm.h         |  1 +
 4 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/share/man/man9/Makefile b/share/man/man9/Makefile
index bcfcb52b0152..1540bfa9d4dd 100644
--- a/share/man/man9/Makefile
+++ b/share/man/man9/Makefile
@@ -414,6 +414,7 @@ MAN=	accept_filter.9 \
 MLINKS=	unr.9 alloc_unr.9 \
 	unr.9 alloc_unrl.9 \
 	unr.9 alloc_unr_specific.9 \
+	unr.9 clear_unrhdr.9 \
 	unr.9 delete_unrhdr.9 \
 	unr.9 free_unr.9 \
 	unr.9 new_unrhdr.9
diff --git a/share/man/man9/unr.9 b/share/man/man9/unr.9
index d8b9d9585352..fe1299d40e5d 100644
--- a/share/man/man9/unr.9
+++ b/share/man/man9/unr.9
@@ -24,11 +24,12 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 5, 2010
+.Dd October 4, 2017
 .Dt UNR 9
 .Os
 .Sh NAME
 .Nm new_unrhdr ,
+.Nm clear_unrhdr ,
 .Nm delete_unrhdr ,
 .Nm alloc_unr ,
 .Nm alloc_unr_specific ,
@@ -39,6 +40,8 @@
 .Ft "struct unrhdr *"
 .Fn new_unrhdr "int low" "int high" "struct mtx *mutex"
 .Ft void
+.Fn clear_unrhdr "struct unrhdr *uh"
+.Ft void
 .Fn delete_unrhdr "struct unrhdr *uh"
 .Ft int
 .Fn alloc_unr "struct unrhdr *uh"
@@ -70,8 +73,16 @@ is not
 .Dv NULL ,
 it is used for locking when allocating and freeing units.
 Otherwise, internal mutex is used.
+.It Fn clear_unrhdr uh
+Clear all units from the specified unit number allocator entity.
+This function resets the entity as if it were just initialized with
+.Fn new_unrhdr .
 .It Fn delete_unrhdr uh
-Destroy specified unit number allocator entity.
+Delete specified unit number allocator entity.
+This function frees the memory associated with the entity, it does not free
+any units.
+To free all units use
+.Fn clear_unrhdr .
 .It Fn alloc_unr uh
 Return a new unit number.
 The lowest free number is always allocated.
diff --git a/sys/kern/subr_unit.c b/sys/kern/subr_unit.c
index 3d510775b9ef..c2110d72169f 100644
--- a/sys/kern/subr_unit.c
+++ b/sys/kern/subr_unit.c
@@ -366,6 +366,27 @@ delete_unrhdr(struct unrhdr *uh)
 	Free(uh);
 }
 
+void
+clear_unrhdr(struct unrhdr *uh)
+{
+	struct unr *up, *uq;
+
+	KASSERT(TAILQ_EMPTY(&uh->ppfree),
+	    ("unrhdr has postponed item for free"));
+	up = TAILQ_FIRST(&uh->head);
+	while (up != NULL) {
+		uq = TAILQ_NEXT(up, list);
+		if (up->ptr != uh) {
+			Free(up->ptr);
+		}
+		Free(up);
+		up = uq;
+	}
+	TAILQ_INIT(&uh->head);
+	uh->busy = 0;
+	uh->alloc = 0;
+}
+
 static __inline int
 is_bitmap(struct unrhdr *uh, struct unr *up)
 {
diff --git a/sys/sys/systm.h b/sys/sys/systm.h
index ddebe0a68431..4fa3e6bb3444 100644
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -450,6 +450,7 @@ struct unrhdr;
 struct unrhdr *new_unrhdr(int low, int high, struct mtx *mutex);
 void init_unrhdr(struct unrhdr *uh, int low, int high, struct mtx *mutex);
 void delete_unrhdr(struct unrhdr *uh);
+void clear_unrhdr(struct unrhdr *uh);
 void clean_unrhdr(struct unrhdr *uh);
 void clean_unrhdrl(struct unrhdr *uh);
 int alloc_unr(struct unrhdr *uh);