Date: Wed, 15 Jun 2011 06:47:29 -0600 From: "Justin T. Gibbs" <gibbs@FreeBSD.org> To: Pawel Jakub Dawidek <pjd@FreeBSD.org> Cc: fs@FreeBSD.org Subject: Re: svn commit: r223089 - in head: sys/cam/ata sys/cam/scsi sys/geom sys/sys usr.sbin/diskinfo Message-ID: <4DF8A9E1.6050501@FreeBSD.org> In-Reply-To: <20110615094202.GB1975@garage.freebsd.pl> References: <201106141710.p5EHAXYS044119@svn.freebsd.org> <20110615094202.GB1975@garage.freebsd.pl>
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On 6/15/11 3:42 AM, Pawel Jakub Dawidek wrote: > On Tue, Jun 14, 2011 at 05:10:33PM +0000, Justin T. Gibbs wrote: > > Author: gibbs > > Date: Tue Jun 14 17:10:32 2011 > > New Revision: 223089 > > URL: http://svn.freebsd.org/changeset/base/223089 > > > > Log: > [...] > > sys/sys/geom/geom.h: > > sys/geom/geom_event.c: > > - Provide the g_attr_changed() function that providers > > can use to advertise attribute changes. > > - Perform delivery of attribute change notifications > > from a thread context via the standard GEOM event > > mechanism. > > Would be nice to discuss it before the commit (or did I miss the > dicussion?). I thought we discussed this at BSDCAN, but perhaps it was when I was talking with mav? Sorry about that. > I was working on something that could be easly merged with > your changes. I had a patch to implement provider's properties change > notification to consumers and devd: > > http://people.freebsd.org/~pjd/patches/geom_property_change.patch > > Currently it implements only mediasize changes, so the upper layers can > act accordingly. The patch also implements ZFS bits to detect vdev size > changes and eventually autoexpand the pool. > > Could you look at the patch and see how we could add property changes to > your API? You say "property," I say "attribute". I used GEOM's string names for properties, you used flags. Other than that, I don't see much difference in the implementations. As far as supporting size changes in the API I committed, the intention is for the API to support notification of arbitrary provider changes, but changes that don't necessarily require consumers to go through a costly "re-taste process". If we define a string constant for the size property, emit that via "g_attr_changed()" in all the places you currently emit g_property_change(), and use strcmp instead of bit tests in your handlers, it should work. If you'd like, I can merge your changes into the API. However, I leave for a two week vacation on Friday, so it will have to be after that. One other issue I need to resolve is that notifying ZFS of things like a physical path change opens us up to lock order reversals. What I'd really like ZFS to do is, during any vdev config generation call, just call a vdev method to refresh attributes. We could then just post a SPA async event from the attr_changed handler and do all of the attribute fetching from the "refresh" method knowing that locks are acquired in the correct order (g_topology last). -- Justin
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