On Tue, 2010-04-27 at 16:21 -0400, Jeff Layton wrote: > I've got a bug report about a possible regression from one of our QA > people. They were testing some of the recent write_inode/COMMIT changes > with this script: > > ----------------[snip]----------------- > #! /usr/bin/env bash > servers="server:/export" > nfsstat -c -3 > > for SRV in $servers > do > mount $SRV /media -o nfsvers=3 > rm -f /media/tmp.file > time dd if=/dev/zero bs=1024k count=2000 of=/media/tmp.file > umount /media > nfsstat -c -3 > done > ----------------[snip]----------------- > > The changes have definitely reduced the number of commit calls, but > frequently we see these errors pop and the filesystem isn't unmounted. > > umount.nfs: /media: device is busy > umount.nfs: /media: device is busy > > ...if I call /bin/sync just before the umount, then it works fine. I > added a cat /proc/meminfo just before the umount and see this: > > MemTotal: 980376 kB > MemFree: 12364 kB > Buffers: 3804 kB > Cached: 803584 kB > SwapCached: 0 kB > Active: 172376 kB > Inactive: 650252 kB > Active(anon): 5592 kB > Inactive(anon): 9808 kB > Active(file): 166784 kB > Inactive(file): 640444 kB > Unevictable: 0 kB > Mlocked: 0 kB > SwapTotal: 2064376 kB > SwapFree: 2064376 kB > Dirty: 0 kB > Writeback: 0 kB > AnonPages: 15240 kB > Mapped: 9008 kB > Shmem: 160 kB > Slab: 123572 kB > SReclaimable: 28096 kB > SUnreclaim: 95476 kB > KernelStack: 1016 kB > PageTables: 2428 kB > NFS_Unstable: 90384 kB > Bounce: 0 kB > WritebackTmp: 0 kB > CommitLimit: 2554564 kB > Committed_AS: 80836 kB > VmallocTotal: 34359738367 kB > VmallocUsed: 41980 kB > VmallocChunk: 34359685244 kB > HardwareCorrupted: 0 kB > AnonHugePages: 0 kB > HugePages_Total: 0 > HugePages_Free: 0 > HugePages_Rsvd: 0 > HugePages_Surp: 0 > Hugepagesize: 2048 kB > DirectMap4k: 8128 kB > DirectMap2M: 1040384 kB > > ...note that Dirty and Writeback are 0, but NFS_Unstable is still at > 90M or so. So, I think the problem is likely that the unstable pages > are preventing the umount. > > I've not done much investigation beyond this yet, but figured I'd toss > the bug report out here in case anyone has thoughts on the cause and > how it should be fixed. I can reproduce this fairly easily on my > virtualized test rig in case anyone has patches that they want me to > test. I'm aware of at least one race in mainline that can result in the above behaviour. There is a proposed fix in the 'bugfixes' branch on linux-nfs.org. See http://git.linux-nfs.org/?p=trondmy/nfs-2.6.git;a=commit;h=71d0a6112a363e703e383ae5b12c492485c39701 Cheers Trond -- 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
