pnfs/blocklayout: use the device id cache

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --cc fs/nfs/blocklayout/blocklayout.c
Simple merge

diff --cc fs/nfs/blocklayout/blocklayout.h
Simple merge

diff --cc fs/nfs/blocklayout/blocklayoutdev.c
Simple merge

diff --cc fs/nfs/blocklayout/blocklayoutdm.c
Simple merge

diff --cc fs/nfs/blocklayout/extent_tree.c
Simple merge