NFSv4.2: LAYOUTSTATS is optional to implement

Make it so, by checking the return value for NFS4ERR_MOTSUPP and
caching the information as a server capability.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs42proc.c

@@ -189,9 +189,15 @@ nfs42_layoutstat_done(struct rpc_task *task, void *calldata)
 	if (!nfs4_sequence_done(task, &data->res.seq_res))
 		return;
 
-	/* well, we don't care about errors at all! */
-	if (task->tk_status)
+	switch (task->tk_status) {
+	case 0:
+		break;
+	case -ENOTSUPP:
+	case -EOPNOTSUPP:
+		NFS_SERVER(data->inode)->caps &= ~NFS_CAP_LAYOUTSTATS;
+	default:
 		dprintk("%s server returns %d\n", __func__, task->tk_status);
+	}
 }
 
 static void

fs/nfs/nfs4proc.c

@@ -8635,7 +8635,8 @@ static const struct nfs4_minor_version_ops nfs_v4_2_minor_ops = {
 		| NFS_CAP_ATOMIC_OPEN_V1
 		| NFS_CAP_ALLOCATE
 		| NFS_CAP_DEALLOCATE
-		| NFS_CAP_SEEK,
+		| NFS_CAP_SEEK
+		| NFS_CAP_LAYOUTSTATS,
 	.init_client = nfs41_init_client,
 	.shutdown_client = nfs41_shutdown_client,
 	.match_stateid = nfs41_match_stateid,

fs/nfs/pnfs.c

@@ -2266,6 +2266,9 @@ pnfs_report_layoutstat(struct inode *inode)
 	if (!pnfs_enabled_sb(server) || !ld->prepare_layoutstats)
 		goto out;
 
+	if (!nfs_server_capable(inode, NFS_CAP_LAYOUTSTATS))
+		goto out;
+
 	if (test_and_set_bit(NFS_INO_LAYOUTSTATS, &nfsi->flags))
 		goto out;
 

include/linux/nfs_fs_sb.h

@@ -237,5 +237,6 @@ struct nfs_server {
 #define NFS_CAP_SEEK		(1U << 19)
 #define NFS_CAP_ALLOCATE	(1U << 20)
 #define NFS_CAP_DEALLOCATE	(1U << 21)
+#define NFS_CAP_LAYOUTSTATS	(1U << 22)
 
 #endif