Merge branch 'flexfiles'

* flexfiles:
  pNFS/flexfiles: Ensure we record layoutstats even if RPC is terminated early
  pNFS: Add flag to track if we've called nfs4_ff_layout_stat_io_start_read/write
  pNFS/flexfiles: Fix a statistics gathering imbalance
  pNFS/flexfiles: Don't mark the entire layout as failed, when returning it
  pNFS/flexfiles: Don't prevent flexfiles client from retrying LAYOUTGET
  pnfs/flexfiles: count io stat in rpc_count_stats callback
  pnfs/flexfiles: do not mark delay-like status as DS failure
  NFS41: map NFS4ERR_LAYOUTUNAVAILABLE to ENODATA
  nfs: only remove page from mapping if launder_page fails
  nfs: handle request add failure properly
  nfs: centralize pgio error cleanup
  nfs: clean up rest of reqs when failing to add one
  NFS41: pop some layoutget errors to application
  pNFS/flexfiles: Support server-supplied layoutstats sampling period