2012/6/25, Fields James <bfields@xxxxxxxxxxxx>: > On Sun, Jun 24, 2012 at 02:12:49PM +0900, Namjae Jeon wrote: >> 2012/6/24, Fields James <bfields@xxxxxxxxxxxx>: >> > On Sat, Jun 23, 2012 at 11:57:10AM -0400, Fields James wrote: >> >> On Sat, Jun 23, 2012 at 03:52:20PM +0000, Myklebust, Trond wrote: >> >> > The other objection is that NFSv3 already has a way to do this via >> >> > the >> >> > MOUNT protocol. We already call MOUNTPROC3_UMNT/MOUNTPROC_UMNT on >> >> > unmount of a filesystem. >> >> > >> >> > The problem with this approach is that if the NFS client crashes >> >> > before >> >> > it can call this function, then the server never gets notified. That >> >> > is >> >> > a problem that your patch has too... >> >> >> >> Yes. Could you instead work on describing *exactly* what the original >> >> problem was that prompted this? >> > >> > ("You" here meaning Namjae Jeon, of course). >> > >> > And note here we've all read the changelog, that's not what I'm asking >> > for. >> > >> > I want to know the details of *your* specific case. "I have X clients >> > that I use for Y, periodically I want to unmount the exported >> > filesystem >> > to do Z, I tried doing W but it didn't work...". >> As you remember, We discussed this >> issue(http://www.spinics.net/lists/linux-nfs/msg29997.html) with you >> before. you guided me to use exportfs -f call on nfs server. >> It is hard to use this method on our system > > Why is it hard? Two target are connected by only nfs.. we can't manually hand exportfs -f.. And I should make each new App on client / server to call exportfs -f. > > Could you hack umount to do the equivalent of "exportfs -f" before > calling the umount? Good Idea! I will check your suggestion. > >> and nomally the user is >> thinking it is problem device busy happen after umounting. >> >> The details of specific case. >> 1. There are two target or two PC. and Client want to access files of >> usb device on server. >> 2. the client try to mount usb mount point using nfs on sever after >> plugging usb device. >> 3. we try to umount mount point directory on client. >> 4. and when we try to umount usb device mount directory server, device >> busy message occured like this (umount: can't umount /mnt: Device or >> resource busy) > > Right, so I don't think you want protocol modifications. They take a > few years to get hammered out and then make it into implementations, and > they won't help a great deal with your problem anyway. (Because of > problems like the possibility of lost "unmount" calls that Trond > mentions.) > > Either modify umount itself to flush the export cache before attempting > the unmount, or if that doesn't work perhaps you could patch the kernel > to notify nfsd on unmount and let it attemt to clear its caches before > deciding whether the filesystem is busy. After checking your suggestion I will share with you. Thanks a lot. James. > > --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