From 2d1ca3cdff784f8171b03e8a0a7425e94773257f Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Sat, 11 Jul 2015 16:28:12 +0000
Subject: [PATCH] vfs: move si_usecount manipulation to dedicated functions

Reviewed by:	kib
---
 sys/kern/vfs_subr.c | 50 +++++++++++++++++++++++++++++++--------------
 1 file changed, 35 insertions(+), 15 deletions(-)

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index a6093bdd40ed..16ad0f360b9e 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -105,6 +105,8 @@ static void	v_incr_usecount(struct vnode *);
 static void	v_decr_usecount(struct vnode *);
 static void	v_decr_useonly(struct vnode *);
 static void	v_upgrade_usecount(struct vnode *);
+static void	v_incr_devcount(struct vnode *);
+static void	v_decr_devcount(struct vnode *);
 static void	vnlru_free(int);
 static void	vgonel(struct vnode *);
 static void	vfs_knllock(void *arg);
@@ -2082,11 +2084,7 @@ v_incr_usecount(struct vnode *vp)
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	vholdl(vp);
 	vp->v_usecount++;
-	if (vp->v_type == VCHR && vp->v_rdev != NULL) {
-		dev_lock();
-		vp->v_rdev->si_usecount++;
-		dev_unlock();
-	}
+	v_incr_devcount(vp);
 }
 
 /*
@@ -2099,11 +2097,7 @@ v_upgrade_usecount(struct vnode *vp)
 
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	vp->v_usecount++;
-	if (vp->v_type == VCHR && vp->v_rdev != NULL) {
-		dev_lock();
-		vp->v_rdev->si_usecount++;
-		dev_unlock();
-	}
+	v_incr_devcount(vp);
 }
 
 /*
@@ -2120,11 +2114,7 @@ v_decr_usecount(struct vnode *vp)
 	    ("v_decr_usecount: negative usecount"));
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	vp->v_usecount--;
-	if (vp->v_type == VCHR && vp->v_rdev != NULL) {
-		dev_lock();
-		vp->v_rdev->si_usecount--;
-		dev_unlock();
-	}
+	v_decr_devcount(vp);
 	vdropl(vp);
 }
 
@@ -2143,6 +2133,36 @@ v_decr_useonly(struct vnode *vp)
 	    ("v_decr_useonly: negative usecount"));
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	vp->v_usecount--;
+	v_decr_devcount(vp);
+}
+
+/*
+ * Increment si_usecount of the associated device, if any.
+ */
+static void
+v_incr_devcount(struct vnode *vp)
+{
+
+#ifdef INVARIANTS
+	/* getnewvnode() calls v_incr_usecount() without holding interlock. */
+	if (vp->v_type != VNON || vp->v_data != NULL)
+		ASSERT_VI_LOCKED(vp, __FUNCTION__);
+#endif
+	if (vp->v_type == VCHR && vp->v_rdev != NULL) {
+		dev_lock();
+		vp->v_rdev->si_usecount++;
+		dev_unlock();
+	}
+}
+
+/*
+ * Decrement si_usecount of the associated device, if any.
+ */
+static void
+v_decr_devcount(struct vnode *vp)
+{
+
+	ASSERT_VI_LOCKED(vp, __FUNCTION__);
 	if (vp->v_type == VCHR && vp->v_rdev != NULL) {
 		dev_lock();
 		vp->v_rdev->si_usecount--;