On Tue, 12 Nov 2013 18:49:34 +0100 Colin Guthrie <gm...@colin.guthr.ie> wrote:
> 'Twas brillig, and NeilBrown at 12/11/13 11:17 did gyre and gimble: > > On Tue, 12 Nov 2013 18:16:24 +0900 Greg KH <gre...@linuxfoundation.org> > > wrote: > > > >> On Tue, Nov 12, 2013 at 07:54:42PM +1100, NeilBrown wrote: > >>> On Tue, 12 Nov 2013 00:10:28 -0800 Greg KH <gre...@linuxfoundation.org> > >>> wrote: > >>> > >>>> On Tue, Nov 12, 2013 at 11:31:45AM +1100, NeilBrown wrote: > >>>>> Alternately, is there some "all devices have been probed, nothing new > >>>>> will > >>>>> appear unless it is hot-plugged" event. That would be equally useful > >>>>> (and > >>>>> probably mirrors what hardware-RAID cards do). > >>>> > >>>> No, there's no way to ever know this in a hotplug world, sorry. > >>>> Especially with USB devices, they show up when they show up, there's no > >>>> "oh look, the bus is all scanned now and all devices currently plugged > >>>> in are found" type knowledge at all. > >>>> > >>>> Then there are hotplug PCI systems where people slam in PCI cards > >>>> whenever they feel like it (remember, thunderbolt is PCI express...) > >>>> > >>>> Sorry, > >>>> > >>>> greg k-h > >>> > >>> Surely something must be possible. > >> > >> For USB, nope, there isn't, sorry. > >> > >>> Clearly a physical hot-plug event will cause more devices to appear, but > >>> there must come a point at which no more (non-virtual) devices will appear > >>> unless a physical event happens? > >> > >> Not for USB, sorry. > >> > >> The USB bus just announces devices when it finds them, there is no "all > >> is quiet" type signal or detection. > >> > >> Same for PCI hotplug, devices can show up at any point in time, you > >> never know when, and you don't know when all devices are "found". > >> > >> sorry, > >> > >> greg k-h > > > > > > Hmmm... OK. USB doesn't bother me a lot, but PCI is important. > > > > I guess I'll just have to settle for a timeout much like the current > > device-discovery timeout that systemd has. > > Still hoping someone can tell me how to plug into that though... > > Wouldn't it be nicer to work on a nice text-UI/wizard type thing that > would allow an admin to manually say "yes, I appreciate that the raid > array is degraded and I would like to start it anyway"? > > It seems to me that doing this automatically is a bad idea if someone > simply forgot to plug in a drive... or, and this has happened to me > (tho' I stress not *by* me!), removes the wrong drive. I guess I'm in > two minds on this one as I can see the usefulness of just coping and > carrying on but the prospect of a multi-day resync with modern large > disks for a simple mistake isn't too nice either! > > There doesn't appear to be any generic way to get user approval for such > interactive questions, but perhaps this is the kind of infrastructure > that should be provided - perhaps similar to the whole password agent thing? > > Maybe this is just all a bit too much tho'... Thanks for the suggestion. However lots of machines are expected to boot unattended and that is the case that I really want to work. I think boot should only fail if it cannot possibly succeed (without risking serious corruption). Thanks, NeilBrown
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