ceph: add get_name() NFS export callback

Use the newly introduced LOOKUPNAME MDS request to connect child
inode to its parent directory.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
ceph: print inode number for LOOKUPINO request

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
vfs: Make __d_materialise_dentry() set the materialised dentry name correctly

Make __d_materialise_dentry() set the materialised dentry name correctly by
flipping the arguments to switch_names().

switch_names() is lazy: if both names are internal to their dentries, it'll
overwrite that of the first dentry with that of the second, and won't update
that of the second.

In the case of __d_materialise_dentry(), the second is an already extant
anonymous dentry that we want to insert into the tree in place of the dentry we
just looked up[*].  However, the dentry we just looked up carries the name we
actually want to use.

[*] This is used by NFS to join a mount of a subtree into a mount of a tree
nearer the root when the two meet, where both mounts share a superblock and
thus a set of dentries.

Signed-off-by: David Howells <dhowells@redhat.com>
ceph: make sure write caps are registered with auth MDS

Only auth MDS can issue write caps to clients, so don't consider
write caps registered with non-auth MDS as valid.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
ceph: update i_max_size even if inode version does not change

handle following sequence of events:
 - client releases a inode with i_max_size > 0. The release message
   is queued.
 - a 'lookup' request reply from non-auth MDS returns the same inode.
 - client opens the inode in write mode. The version of inode trace
   in 'open' request reply is equal to the cached inode's version.
 - client requests new max size. But the MDS ignores the request
   because the request does not affect client's write range

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>