From a02e196edd4a89d7c2582312d8e77c84f215487b Mon Sep 17 00:00:00 2001
From: "Kenneth D. Merry" <ken@FreeBSD.org>
Date: Thu, 23 Jun 2016 20:05:59 +0000
Subject: [PATCH] Switch geom_disk over to using a pool mutex.

The GEOM disk d_mtx is only acquired on disk creation and destruction.
It is a good candidate for replacement with a pool mutex.  This eliminates
the mutex initialization and teardown and the mutex and name variables
themselves from struct disk.

sys/geom/geom_disk.h:
	Take d_mtx and d_mtx_name out of struct disk.

sys/geom/geom_disk.c:
	Use mtx_pool_lock() and mtx_pool_unlock() to guard the disk
	initialization state instead of a dedicated mutex.

	This allows removing the initialization and destruction of
	d_mtx.

sys/sys/param.h:
	Bump __FreeBSD_version to 1100119 for the change to struct disk.

Suggested by:	jhb
Sponsored by:	Spectra Logic
Approved by:	re (gjb)
---
 sys/geom/geom_disk.c | 23 +++++++++--------------
 sys/geom/geom_disk.h |  2 --
 sys/sys/param.h      |  2 +-
 3 files changed, 10 insertions(+), 17 deletions(-)

diff --git a/sys/geom/geom_disk.c b/sys/geom/geom_disk.c
index 37770f938c5..e4b1e141b54 100644
--- a/sys/geom/geom_disk.c
+++ b/sys/geom/geom_disk.c
@@ -670,7 +670,7 @@ g_disk_create(void *arg, int flag)
 	g_topology_assert();
 	dp = arg;
 
-	mtx_lock(&dp->d_mtx);
+	mtx_pool_lock(mtxpool_sleep, dp);
 	dp->d_init_level = DISK_INIT_START;
 
 	/*
@@ -678,12 +678,12 @@ g_disk_create(void *arg, int flag)
 	 * call the user's callback to tell him we've cleaned things up.
 	 */
 	if (dp->d_goneflag != 0) {
-		mtx_unlock(&dp->d_mtx);
+		mtx_pool_unlock(mtxpool_sleep, dp);
 		if (dp->d_gone != NULL)
 			dp->d_gone(dp);
 		return;
 	}
-	mtx_unlock(&dp->d_mtx);
+	mtx_pool_unlock(mtxpool_sleep, dp);
 
 	sc = g_malloc(sizeof(*sc), M_WAITOK | M_ZERO);
 	mtx_init(&sc->start_mtx, "g_disk_start", NULL, MTX_DEF);
@@ -721,7 +721,7 @@ g_disk_create(void *arg, int flag)
 	dp->d_geom = gp;
 	g_error_provider(pp, 0);
 
-	mtx_lock(&dp->d_mtx);
+	mtx_pool_lock(mtxpool_sleep, dp);
 	dp->d_init_level = DISK_INIT_DONE;
 
 	/*
@@ -729,11 +729,11 @@ g_disk_create(void *arg, int flag)
 	 * process for it.
 	 */
 	if (dp->d_goneflag != 0) {
-		mtx_unlock(&dp->d_mtx);
+		mtx_pool_unlock(mtxpool_sleep, dp);
 		g_wither_provider(pp, ENXIO);
 		return;
 	}
-	mtx_unlock(&dp->d_mtx);
+	mtx_pool_unlock(mtxpool_sleep, dp);
 
 }
 
@@ -786,8 +786,6 @@ g_disk_destroy(void *ptr, int flag)
 		g_wither_geom(gp, ENXIO);
 	}
 
-	mtx_destroy(&dp->d_mtx);
-
 	g_free(dp);
 }
 
@@ -852,9 +850,6 @@ disk_create(struct disk *dp, int version)
 		    DEVSTAT_TYPE_DIRECT, DEVSTAT_PRIORITY_MAX);
 	dp->d_geom = NULL;
 
-	snprintf(dp->d_mtx_name, sizeof(dp->d_mtx_name), "%s%ddlk",
-		 dp->d_name, dp->d_unit);
-	mtx_init(&dp->d_mtx, dp->d_mtx_name, NULL, MTX_DEF);
 	dp->d_init_level = DISK_INIT_NONE;
 
 	g_disk_ident_adjust(dp->d_ident, sizeof(dp->d_ident));
@@ -878,7 +873,7 @@ disk_gone(struct disk *dp)
 	struct g_geom *gp;
 	struct g_provider *pp;
 
-	mtx_lock(&dp->d_mtx);
+	mtx_pool_lock(mtxpool_sleep, dp);
 	dp->d_goneflag = 1;
 
 	/*
@@ -897,10 +892,10 @@ disk_gone(struct disk *dp)
 	 * has not been fully setup in any case.
 	 */
 	if (dp->d_init_level < DISK_INIT_DONE) {
-		mtx_unlock(&dp->d_mtx);
+		mtx_pool_unlock(mtxpool_sleep, dp);
 		return;
 	}
-	mtx_unlock(&dp->d_mtx);
+	mtx_pool_unlock(mtxpool_sleep, dp);
 
 	gp = dp->d_geom;
 	if (gp != NULL) {
diff --git a/sys/geom/geom_disk.h b/sys/geom/geom_disk.h
index 8549348faf6..5fce5b93f69 100644
--- a/sys/geom/geom_disk.h
+++ b/sys/geom/geom_disk.h
@@ -72,8 +72,6 @@ struct disk {
 	struct devstat		*d_devstat;
 	int			d_goneflag;
 	int			d_destroyed;
-	struct mtx		d_mtx;
-	char			d_mtx_name[24];
 	disk_init_level		d_init_level;
 
 	/* Shared fields */
diff --git a/sys/sys/param.h b/sys/sys/param.h
index 203b6efdb9d..e254573a606 100644
--- a/sys/sys/param.h
+++ b/sys/sys/param.h
@@ -58,7 +58,7 @@
  *		in the range 5 to 9.
  */
 #undef __FreeBSD_version
-#define __FreeBSD_version 1100118	/* Master, propagated to newvers */
+#define __FreeBSD_version 1100119	/* Master, propagated to newvers */
 
 /*
  * __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,