From fe39412e99d2ad2bc77575d08efdc199c08ba94d Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Sun, 29 Sep 2013 18:07:14 +0000
Subject: [PATCH] For vunref(), try to upgrade the vnode lock if the function
 was called with the vnode shared-locked.  If upgrade succeeded, the
 inactivation can be done immediately, instead of being postponed.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Approved by:	re (glebius)
---
 sys/kern/vfs_subr.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 23343f12a1b..952a48990d2 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -2218,8 +2218,10 @@ vputx(struct vnode *vp, int func)
 		}
 		break;
 	case VPUTX_VUNREF:
-		if (VOP_ISLOCKED(vp) != LK_EXCLUSIVE)
-			error = EBUSY;
+		if (VOP_ISLOCKED(vp) != LK_EXCLUSIVE) {
+			error = VOP_LOCK(vp, LK_TRYUPGRADE | LK_INTERLOCK);
+			VI_LOCK(vp);
+		}
 		break;
 	}
 	if (vp->v_usecount > 0)