On Thu, Jul 12, 2012 at 07:43:49AM +0900, Namjae Jeon wrote: > 2012/7/12, Namjae Jeon <linkinjeon@xxxxxxxxx>: > > 2012/7/11, J. Bruce Fields <bfields@xxxxxxxxxxxx>: > >> On Wed, Jul 11, 2012 at 01:10:53PM +0900, Namjae Jeon wrote: > >>> 2012/7/10, J. Bruce Fields <bfields@xxxxxxxxxxxx>: > >>> > On Sat, Jul 07, 2012 at 11:17:39PM -0400, Namjae Jeon wrote: > >>> >> For removing storage device - user needs to safely un-mount the > >>> >> device > >>> >> and then eject. But if 'EBUSY' occurs in umount then it will create > >>> >> confusion for the user as it will mean some I/O is in progress - and > >>> >> won't allow user to safely ejecting device. > >>> > > >>> Hi James. > >>> > The one drawback is that recovering from the cache flushes might be a > >>> > little expensive if you have a lot of exports in use. > >>> Good point. I will look for more there is the method flush only mount > >>> entry. > >> > >> I don't think there's a good way to flush only one entry. > >> > >> Also, this isn't going to help for NFSv4 since a v4 client won't do an > >> unmount call. > > Okay. > >> > >>> > I'm curious, since you said this was for a usb disk: are users > >>> > expected > >>> > to just unplug it (in which case--is it read only?) or do they have > >>> > some > >>> > way of unmounting before they pull the plug? > >>> Users expected to unplug it on both read only and read/write. > >>> And there is no way that system be prepared to know about the > >>> intelligence when the user is going to unplug. > >>> if the user really want to detach the device safely. There is an > >>> option like the desktop PC - where, we can say - umount/eject the > >>> device. There is a proper user interface for safe removal. > >>> but they can not unplug safely if usb device is mounted with nfs > >>> because of this issue. > >> > >> Ideal might be to get some way to notify nfsd when the device > >> diseappears or the filesystem wants to unmount. I don't know how to do > >> that. > > Okay. I will look for good solution for this issue. > > Thanks. > Hi James. > I have a question. > If we found the method to notify nfs when unplugging device, What's that? > Can nfsd > flush only entry of usb mount ? Hm, I don't think there's anything that does that now. But I think if you look it up and set the cache item's expiry_time to the current unix time in seconds, that'd be at least a start. Come to think of it you should actually be able to do that from userspace if you want: just write a negative cache entry for that export. However you do this there may still be some brief delay while some thread finishes processing an rpc using the entry; I don't know what to do about that. It's unlikely in your case (where clients have unmounted first). --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
