PROBLEM: knfsd misses occasional writes

[Sverker Wiberg]

Hello everyone, 

When copying lots of small files from multiple NFS clients to a kNFSd
filesystem (i.e. doing backup of a cluster), exported with `sync', I
find that some few files (1 out of 1000) were silently truncated to zero
size when checking locally with `ls' (the clients reported total
success). With `asynch' instead, all files were correctly copied. 

I have seen this behaviour in 2.4.17 (UP and SMP builds, UP hardware) as
well as 2.4.18, when using the NFSv2 protocol. I have not tried 2.5.x
and NFSv3 yet. The full /etc/exports line is:

   /opt/telorb 172.16.0.0/255.255.0.0(rw,sync,no_wdelay)

Removing `no_wdelay' makes no difference.

The clients are all 2.4.17, and the relevant .config lines (for both
server and clients) are:

   CONFIG_NFS_FS=y
   CONFIG_NFS_V3=y
   CONFIG_ROOT_NFS=y
   CONFIG_NFSD=y
   CONFIG_NFSD_V3=y
   CONFIG_SUNRPC=y
   CONFIG_LOCKD=y
   CONFIG_LOCKD_V4=y

Reading the source (fs/nfsd/*) seems to show that knfsd tries to do the
right thing.

/Sverker Wiberg