ceph: inode operations

ceph: inode operations

Inode cache and inode operations.  We also include routines to
incorporate metadata structures returned by the MDS into the client
cache, and some helpers to deal with file capabilities and metadata
leases.  The bulk of that work is done by fill_inode() and
fill_trace().

Most MDS responses include a "trace" of dentry and inode information
from the inode in question back to the root.  fill_trace() takes pains
to ensure that the dcache is updated safely.  If the directory i_mutex
is not already held and cannot be taken (via trylock), that segment of
the trace is skipped.  If an inode is linked incorrectly, we attempt
to reattach it in the correct position in the hierarchy.