On Tue, 27 Apr 2010 17:18:06 -0400 Trond Myklebust <Trond.Myklebust@xxxxxxxxxx> wrote: > 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 > Thanks Trond, that patch does seem to fix it. FWIW, the kernel I saw this on did not have commit 2c61be0a9478258f77b66208a0c4b1f5f8161c3c, so apparently the race can manifest itself without that commit. Cheers, -- Jeff Layton <jlayton@xxxxxxxxxx> -- 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
