From owner-svn-src-all@FreeBSD.ORG Mon May 17 15:45:54 2010 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 95BA5106566C; Mon, 17 May 2010 15:45:54 +0000 (UTC) (envelope-from matthew.fleming@isilon.com) Received: from seaxch09.isilon.com (seaxch09.isilon.com [74.85.160.25]) by mx1.freebsd.org (Postfix) with ESMTP id 733018FC16; Mon, 17 May 2010 15:45:54 +0000 (UTC) X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Date: Mon, 17 May 2010 08:33:52 -0700 Message-ID: <06D5F9F6F655AD4C92E28B662F7F853E021D4D66@seaxch09.desktop.isilon.com> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: svn commit: r208003 - in head/sys: kern sys Thread-Index: Acr0tZ24VvXcICWfSciYrg8DiAvBhwBH5f1R References: <201005122124.o4CLOk3b027904@svn.freebsd.org> <20100516050651.GZ83316@deviant.kiev.zoral.com.ua> From: "Matthew Fleming" To: "Kostik Belousov" , "Zachary Loafman" Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: RE: svn commit: r208003 - in head/sys: kern sys X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 17 May 2010 15:45:54 -0000 > From: Kostik Belousov [mailto:kostikbel@gmail.com] > On Wed, May 12, 2010 at 09:24:46PM +0000, Zachary Loafman wrote: > > Author: zml > > Date: Wed May 12 21:24:46 2010 > > New Revision: 208003 > > URL: http://svn.freebsd.org/changeset/base/208003 > >=20 > > Log: > > Add VOP_ADVLOCKPURGE so that the file system is called when = purging > > locks (in the case where the VFS impl isn't using lf_*) > > =20 > > Submitted by: Matthew Fleming > > Reviewed by: zml, dfr >=20 > After looking at what happen to nullfs, see r208003, I wonder why > the vop is needed. It is called after VOP_RECLAIM is called by = vgonel(), > after fs-specific data are destroyed. So, on the one hand, vop can = only > operate on struct vnode proper, on the other hand, the actions = performed > by vop_advlockpurge implementation can be done by vop_reclaim as well. >=20 > Could you, please, give some details on the supposed use of the vop ? >From a design perspective, it makes little sense to allow overriding the = advlock operation, but not the purge. A specific example is if an = implementation does not use struct lockf to implement advlock, then the = hack you mention of purging in VOP_RECLAIM is needed. After looking over the history of the changes, I believe it would be = sufficient to have the lock purge done before the reclaim. The vnode is = locked exclusively for both operations, so I don't believe there will be = any timing windows. But I am still not 100% sure when the file lock is = used versus the interlock for serializing access to various fields. The advlock VOPs are analogous to the regular VOP_LOCK in that we expect = an implementation may override the VOP and also the data structures = used, e.g. to not use the vnode's v_lock field for the VOP_LOCK. Thus = any code which refers to v_lockf should be wrapped in a VOP to allow = correct overriding. Thanks, matthew