On Thu, Jan 08, 2015 at 01:43:27PM +0100, Christoph Hellwig wrote: > On Thu, Jan 08, 2015 at 08:11:40AM +1100, Dave Chinner wrote: > > So what happens if a grow occurs, then the server crashes, and the > > client on reboot sees the same generation as before the grow > > occured? > > The client doesn't really see the generation. It's party of the deviceid, > which is opaqueue to the client. > > If the client sends the opaqueue device ID that contains the generation > after the grow to a server that had crashed / restarted the server > will reject it as the server starts at zero. The causes the client > to get a new, valid device ID from the server. But if the server fs has a generation number of zero when it crashes, how does the client tell that it needs a new device ID from the server? > Unlike the NFS file hadles which are persistent the device IDs are volatile > handles that can go away (and have really horrible life time rules..). Right. How the clients detect that "going away" when the device generation is zero both before and after a server crash is the question I'm asking.... > > > So that we can communicate if a device was grown to the client, which > > > in this case needs to re-read the device information. > > > > Why does it need to reread the device information? the layouts that > > are handled to it are still going to be valid from the server POV... > > The existing layouts are still valid. But any new layout can reference the > added size, so any new layout needs to point to the new device ID. > > Once the client sees the new device ID it needs to get the information for > it, which causes it to re-read the device information. OK. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
