[PATCH 0/1] NFSv4.1 Fix umount when filelayout DS is also the MDS

[andros@netapp.com]

From: Andy Adamson <andros@netapp.com>

At the Bakeathon, Jorge noted that when the MDS and DS use the same struct
nfs_client, umount would fail to free the nfs_client struct and the
keep-alive SEQUENCE compound would continue ad infinitum.

This was due to the fact that the DS reference to the MDS nfs_client would
prevent the umount from dropping the cl_count to zero. Moreover, the
DS refererence is only dropped by the deviceid dereference only called
by nfs4_deviceid_purge_client from nfs_free_client when the nfs_client
cl_count was zero.

See the patch comments for the solution description.

I've tested this solution against a 2-node C-mode filer where one node is an
MDS/DS and the other node a standalone MDS but uses the first node as a DS.

I tested all combinations, including mounting the MDS/DS node, and using pNFS
for I/O. Then mounting the solo MDS node, and using pNFS for I/O (which uses
the MDS/DS node as a DS), then umounting one of the mount points, doing pNFS
I/O and then umount the other.

In all cases, umount destroyed the appropriate nfs_client, and associated
session.

Andy Adamson (1):
  NFSv4.1 Fix umount when filelayout DS is also the MDS

 fs/nfs/client.c            |   71 ++++++++++++++++++++++++++++++++++++++++++--
 fs/nfs/internal.h          |    1 +
 fs/nfs/nfs4filelayoutdev.c |   29 +++++++++++++++--
 include/linux/nfs_fs_sb.h  |    1 +
 4 files changed, 95 insertions(+), 7 deletions(-)

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1.7.6.4