Date: Sun, 30 Jan 2005 15:37:03 +0000 (GMT) From: Robert Watson <rwatson@FreeBSD.org> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: Warner Losh <imp@rover.village.org> Subject: Re: Devd event from GEOM? Message-ID: <Pine.NEB.3.96L.1050130153532.15336I-100000@fledge.watson.org> In-Reply-To: <69175.1107098435@critter.freebsd.dk>
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On Sun, 30 Jan 2005, Poul-Henning Kamp wrote: > In message <20050130161323.5e25414e@Magellan.Leidinger.net>, Alexander Leidinger writes: > > >Let's take a CD for example, when it arrives the auto-mounter mounts it. > >Fine, but the CD is locked then. What do we do when we want to remove > >the CD? Or another example, an USB stick. The hardware isn't locked, but > >when we just remove it, we're calling for a kernel panic. > > Now that local-storage filesystems are GEOM users, we can actually get > the "orphan" event from GEOM communicated to the filesystem which can > then take proper evasive action. No filesystem has implemented this yet. I think tolerance of hard removal faults will always be a tricky issue -- we can clearly handle it better than we do today. The user losing data is fine: if you don't want to lose data, you have to arrange for a clean unmount. However, today's panic is a bit extreme. The good news is that soft eject is a lot easier to handle, as it's more of a question of signalling and management than hard technical issues in how to tear down state at a bad moment in the kernel. Robert N M Watson
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