nfs/filelayout: set layoutcommit depending on write verifier

Following http://www.rfc-editor.org/errata_search.php?rfc=5661&eid=2751
Don't set layoutcommit for commit_through_mds case.
For FILE_SYNC writes, don't set layoutcommit.
For DATA_SYNC wirtes, set layout commit right after wirtes done.
For UNSTABLE writes, set layout commit when commit done.
Signed-off-by: NPeng Tao <tao.peng@primarydata.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/filelayout/filelayout.c

@@ -265,7 +265,7 @@ filelayout_set_layoutcommit(struct nfs_pgio_header *hdr)
 {
 
 	if (FILELAYOUT_LSEG(hdr->lseg)->commit_through_mds ||
-	    hdr->res.verf->committed == NFS_FILE_SYNC)
+	    hdr->res.verf->committed != NFS_DATA_SYNC)
 		return;
 
 	pnfs_set_layoutcommit(hdr);
@@ -403,6 +403,9 @@ static int filelayout_commit_done_cb(struct rpc_task *task,
 		return -EAGAIN;
 	}
 
+	if (data->verf.committed == NFS_UNSTABLE)
+		pnfs_commit_set_layoutcommit(data);
+
 	return 0;
 }