NFSv4: Add support for the NFSv4.2 "change_attr_type" attribute

The change_attr_type allows the server to provide a description of how
the change attribute will behave. This again will allow the client to
optimise its behaviour w.r.t. attribute revalidation.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/client.c

@@ -792,6 +792,7 @@ static void nfs_server_set_fsinfo(struct nfs_server *server,
 	server->maxfilesize = fsinfo->maxfilesize;
 
 	server->time_delta = fsinfo->time_delta;
+	server->change_attr_type = fsinfo->change_attr_type;
 
 	server->clone_blksize = fsinfo->clone_blksize;
 	/* We're airborne Set socket buffersize */
@@ -933,6 +934,8 @@ struct nfs_server *nfs_alloc_server(void)
 		return NULL;
 	}
 
+	server->change_attr_type = NFS4_CHANGE_TYPE_IS_UNDEFINED;
+
 	ida_init(&server->openowner_id);
 	ida_init(&server->lockowner_id);
 	pnfs_init_server(server);

fs/nfs/nfs3xdr.c

@@ -2227,6 +2227,7 @@ static int decode_fsinfo3resok(struct xdr_stream *xdr,
 
 	/* ignore properties */
 	result->lease_time = 0;
+	result->change_attr_type = NFS4_CHANGE_TYPE_IS_TIME_METADATA;
 	return 0;
 }
 

fs/nfs/nfs4proc.c

@@ -264,6 +264,7 @@ const u32 nfs4_fsinfo_bitmap[3] = { FATTR4_WORD0_MAXFILESIZE
 			| FATTR4_WORD1_FS_LAYOUT_TYPES,
 			FATTR4_WORD2_LAYOUT_BLKSIZE
 			| FATTR4_WORD2_CLONE_BLKSIZE
+			| FATTR4_WORD2_CHANGE_ATTR_TYPE
 			| FATTR4_WORD2_XATTR_SUPPORT
 };
 

fs/nfs/nfs4xdr.c

@@ -153,6 +153,7 @@ static int decode_layoutget(struct xdr_stream *xdr, struct rpc_rqst *req,
 				 5 /* fs layout types */ + \
 				 1 /* layout blksize */ + \
 				 1 /* clone blksize */ + \
+				 1 /* change attr type */ + \
 				 1 /* xattr support */)
 #define encode_renew_maxsz	(op_encode_hdr_maxsz + 3)
 #define decode_renew_maxsz	(op_decode_hdr_maxsz)
@@ -4846,6 +4847,32 @@ static int decode_attr_clone_blksize(struct xdr_stream *xdr, uint32_t *bitmap,
 	return 0;
 }
 
+static int decode_attr_change_attr_type(struct xdr_stream *xdr,
+					uint32_t *bitmap,
+					enum nfs4_change_attr_type *res)
+{
+	u32 tmp = NFS4_CHANGE_TYPE_IS_UNDEFINED;
+
+	dprintk("%s: bitmap is %x\n", __func__, bitmap[2]);
+	if (bitmap[2] & FATTR4_WORD2_CHANGE_ATTR_TYPE) {
+		if (xdr_stream_decode_u32(xdr, &tmp))
+			return -EIO;
+		bitmap[2] &= ~FATTR4_WORD2_CHANGE_ATTR_TYPE;
+	}
+
+	switch(tmp) {
+	case NFS4_CHANGE_TYPE_IS_MONOTONIC_INCR:
+	case NFS4_CHANGE_TYPE_IS_VERSION_COUNTER:
+	case NFS4_CHANGE_TYPE_IS_VERSION_COUNTER_NOPNFS:
+	case NFS4_CHANGE_TYPE_IS_TIME_METADATA:
+		*res = tmp;
+		break;
+	default:
+		*res = NFS4_CHANGE_TYPE_IS_UNDEFINED;
+	}
+	return 0;
+}
+
 static int decode_fsinfo(struct xdr_stream *xdr, struct nfs_fsinfo *fsinfo)
 {
 	unsigned int savep;
@@ -4894,6 +4921,11 @@ static int decode_fsinfo(struct xdr_stream *xdr, struct nfs_fsinfo *fsinfo)
 	if (status)
 		goto xdr_error;
 
+	status = decode_attr_change_attr_type(xdr, bitmap,
+					      &fsinfo->change_attr_type);
+	if (status)
+		goto xdr_error;
+
 	status = decode_attr_xattrsupport(xdr, bitmap,
 					  &fsinfo->xattr_support);
 	if (status)

fs/nfs/proc.c

@@ -91,6 +91,7 @@ nfs_proc_get_root(struct nfs_server *server, struct nfs_fh *fhandle,
 	info->dtpref = fsinfo.tsize;
 	info->maxfilesize = 0x7FFFFFFF;
 	info->lease_time = 0;
+	info->change_attr_type = NFS4_CHANGE_TYPE_IS_TIME_METADATA;
 	return 0;
 }
 

include/linux/nfs4.h

@@ -452,6 +452,7 @@ enum lock_type4 {
 #define FATTR4_WORD2_LAYOUT_BLKSIZE     (1UL << 1)
 #define FATTR4_WORD2_MDSTHRESHOLD       (1UL << 4)
 #define FATTR4_WORD2_CLONE_BLKSIZE	(1UL << 13)
+#define FATTR4_WORD2_CHANGE_ATTR_TYPE	(1UL << 15)
 #define FATTR4_WORD2_SECURITY_LABEL     (1UL << 16)
 #define FATTR4_WORD2_MODE_UMASK		(1UL << 17)
 #define FATTR4_WORD2_XATTR_SUPPORT	(1UL << 18)
@@ -709,6 +710,14 @@ struct nl4_server {
 	} u;
 };
 
+enum nfs4_change_attr_type {
+	NFS4_CHANGE_TYPE_IS_MONOTONIC_INCR = 0,
+	NFS4_CHANGE_TYPE_IS_VERSION_COUNTER = 1,
+	NFS4_CHANGE_TYPE_IS_VERSION_COUNTER_NOPNFS = 2,
+	NFS4_CHANGE_TYPE_IS_TIME_METADATA = 3,
+	NFS4_CHANGE_TYPE_IS_UNDEFINED = 4,
+};
+
 /*
  * Options for setxattr. These match the flags for setxattr(2).
  */

include/linux/nfs_fs_sb.h

@@ -180,6 +180,9 @@ struct nfs_server {
 #define NFS_OPTION_FSCACHE	0x00000001	/* - local caching enabled */
 #define NFS_OPTION_MIGRATION	0x00000002	/* - NFSv4 migration enabled */
 
+	enum nfs4_change_attr_type
+				change_attr_type;/* Description of change attribute */
+
 	struct nfs_fsid		fsid;
 	__u64			maxfilesize;	/* maximum file size */
 	struct timespec64	time_delta;	/* smallest time granularity */

include/linux/nfs_xdr.h

@@ -152,6 +152,8 @@ struct nfs_fsinfo {
 	__u32			layouttype[NFS_MAX_LAYOUT_TYPES]; /* supported pnfs layout driver */
 	__u32			blksize; /* preferred pnfs io block size */
 	__u32			clone_blksize; /* granularity of a CLONE operation */
+	enum nfs4_change_attr_type
+				change_attr_type; /* Info about change attr */
 	__u32			xattr_support; /* User xattrs supported */
 };