From owner-svn-src-all@FreeBSD.ORG  Sun Oct  6 06:09:43 2013
Return-Path: <owner-svn-src-all@FreeBSD.ORG>
Delivered-To: svn-src-all@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTP id BF04C538;
 Sun,  6 Oct 2013 06:09:43 +0000 (UTC) (envelope-from kib@FreeBSD.org)
Received: from svn.freebsd.org (svn.freebsd.org
 [IPv6:2001:1900:2254:2068::e6a:0])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (No client certificate requested)
 by mx1.freebsd.org (Postfix) with ESMTPS id AAB822915;
 Sun,  6 Oct 2013 06:09:43 +0000 (UTC)
Received: from svn.freebsd.org ([127.0.1.70])
 by svn.freebsd.org (8.14.7/8.14.7) with ESMTP id r9669hNw028287;
 Sun, 6 Oct 2013 06:09:43 GMT (envelope-from kib@svn.freebsd.org)
Received: (from kib@localhost)
 by svn.freebsd.org (8.14.7/8.14.5/Submit) id r9669hQM028286;
 Sun, 6 Oct 2013 06:09:43 GMT (envelope-from kib@svn.freebsd.org)
Message-Id: <201310060609.r9669hQM028286@svn.freebsd.org>
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Sun, 6 Oct 2013 06:09:43 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org
Subject: svn commit: r256077 - stable/9/sys/kern
X-SVN-Group: stable-9
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
X-BeenThere: svn-src-all@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: "SVN commit messages for the entire src tree \(except for &quot;
 user&quot; and &quot; projects&quot; \)" <svn-src-all.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/svn-src-all>,
 <mailto:svn-src-all-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-all>
List-Post: <mailto:svn-src-all@freebsd.org>
List-Help: <mailto:svn-src-all-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-all>,
 <mailto:svn-src-all-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 06 Oct 2013 06:09:43 -0000

Author: kib
Date: Sun Oct  6 06:09:43 2013
New Revision: 256077
URL: http://svnweb.freebsd.org/changeset/base/256077

Log:
  MFC r255941:
  Increase the chance of the buffer write from the bufdaemon helper
  context to succeed. If the locked vnode which owns the buffer to be
  written is shared locked, try the non-blocking upgrade of the lock to
  exclusive.

Modified:
  stable/9/sys/kern/vfs_bio.c
Directory Properties:
  stable/9/sys/   (props changed)

Modified: stable/9/sys/kern/vfs_bio.c
==============================================================================
--- stable/9/sys/kern/vfs_bio.c	Sun Oct  6 06:05:11 2013	(r256076)
+++ stable/9/sys/kern/vfs_bio.c	Sun Oct  6 06:09:43 2013	(r256077)
@@ -2671,6 +2671,8 @@ flushbufqueues(struct vnode *lvp, int qu
 	int hasdeps;
 	int flushed;
 	int target;
+	int error;
+	bool unlock;
 
 	if (lvp == NULL) {
 		target = numdirtybuffers - lodirtybuffers;
@@ -2751,7 +2753,16 @@ flushbufqueues(struct vnode *lvp, int qu
 			BUF_UNLOCK(bp);
 			continue;
 		}
-		if (vn_lock(vp, LK_EXCLUSIVE | LK_NOWAIT | LK_CANRECURSE) == 0) {
+		if (lvp == NULL) {
+			unlock = true;
+			error = vn_lock(vp, LK_EXCLUSIVE | LK_NOWAIT);
+		} else {
+			ASSERT_VOP_LOCKED(vp, "getbuf");
+			unlock = false;
+			error = VOP_ISLOCKED(vp) == LK_EXCLUSIVE ? 0 :
+			    vn_lock(vp, LK_TRYUPGRADE);
+		}
+		if (error == 0) {
 			mtx_unlock(&bqlock);
 			CTR3(KTR_BUF, "flushbufqueue(%p) vp %p flags %X",
 			    bp, bp->b_vp, bp->b_flags);
@@ -2763,7 +2774,8 @@ flushbufqueues(struct vnode *lvp, int qu
 				notbufdflashes++;
 			}
 			vn_finished_write(mp);
-			VOP_UNLOCK(vp, 0);
+			if (unlock)
+				VOP_UNLOCK(vp, 0);
 			flushwithdeps += hasdeps;
 			flushed++;