NFSv2/v3: Simulate the change attribute

Use the ctime to simulate a change attribute for NFSv2 and NFSv3.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/client.c

@@ -880,7 +880,7 @@ static int nfs_init_server(struct nfs_server *server,
 	server->options = data->options;
 	server->caps |= NFS_CAP_HARDLINKS|NFS_CAP_SYMLINKS|NFS_CAP_FILEID|
 		NFS_CAP_MODE|NFS_CAP_NLINK|NFS_CAP_OWNER|NFS_CAP_OWNER_GROUP|
-		NFS_CAP_ATIME|NFS_CAP_CTIME|NFS_CAP_MTIME;
+		NFS_CAP_ATIME|NFS_CAP_CTIME|NFS_CAP_MTIME|NFS_CAP_CHANGE_ATTR;
 
 	if (data->rsize)
 		server->rsize = nfs_block_size(data->rsize, NULL);

fs/nfs/internal.h

@@ -493,3 +493,15 @@ unsigned int nfs_page_array_len(unsigned int base, size_t len)
 		PAGE_SIZE - 1) >> PAGE_SHIFT;
 }
 
+/*
+ * Convert a struct timespec into a 64-bit change attribute
+ *
+ * This does approximately the same thing as timespec_to_ns(),
+ * but for calculation efficiency, we multiply the seconds by
+ * 1024*1024*1024.
+ */
+static inline
+u64 nfs_timespec_to_change_attr(const struct timespec *ts)
+{
+	return ((u64)ts->tv_sec << 30) + ts->tv_nsec;
+}

fs/nfs/nfs2xdr.c

@@ -313,6 +313,8 @@ static int decode_fattr(struct xdr_stream *xdr, struct nfs_fattr *fattr)
 	p = xdr_decode_time(p, &fattr->atime);
 	p = xdr_decode_time(p, &fattr->mtime);
 	xdr_decode_time(p, &fattr->ctime);
+	fattr->change_attr = nfs_timespec_to_change_attr(&fattr->ctime);
+
 	return 0;
 out_overflow:
 	print_overflow_msg(__func__, xdr);

fs/nfs/nfs3xdr.c

@@ -675,6 +675,7 @@ static int decode_fattr3(struct xdr_stream *xdr, struct nfs_fattr *fattr)
 	p = xdr_decode_nfstime3(p, &fattr->atime);
 	p = xdr_decode_nfstime3(p, &fattr->mtime);
 	xdr_decode_nfstime3(p, &fattr->ctime);
+	fattr->change_attr = nfs_timespec_to_change_attr(&fattr->ctime);
 
 	fattr->valid |= NFS_ATTR_FATTR_V3;
 	return 0;
@@ -725,12 +726,14 @@ static int decode_wcc_attr(struct xdr_stream *xdr, struct nfs_fattr *fattr)
 		goto out_overflow;
 
 	fattr->valid |= NFS_ATTR_FATTR_PRESIZE
+		| NFS_ATTR_FATTR_PRECHANGE
 		| NFS_ATTR_FATTR_PREMTIME
 		| NFS_ATTR_FATTR_PRECTIME;
 
 	p = xdr_decode_size3(p, &fattr->pre_size);
 	p = xdr_decode_nfstime3(p, &fattr->pre_mtime);
 	xdr_decode_nfstime3(p, &fattr->pre_ctime);
+	fattr->pre_change_attr = nfs_timespec_to_change_attr(&fattr->pre_ctime);
 
 	return 0;
 out_overflow:

include/linux/nfs_xdr.h

@@ -106,14 +106,14 @@ struct nfs_fattr {
 		| NFS_ATTR_FATTR_FILEID \
 		| NFS_ATTR_FATTR_ATIME \
 		| NFS_ATTR_FATTR_MTIME \
-		| NFS_ATTR_FATTR_CTIME)
+		| NFS_ATTR_FATTR_CTIME \
+		| NFS_ATTR_FATTR_CHANGE)
 #define NFS_ATTR_FATTR_V2 (NFS_ATTR_FATTR \
 		| NFS_ATTR_FATTR_BLOCKS_USED)
 #define NFS_ATTR_FATTR_V3 (NFS_ATTR_FATTR \
 		| NFS_ATTR_FATTR_SPACE_USED)
 #define NFS_ATTR_FATTR_V4 (NFS_ATTR_FATTR \
-		| NFS_ATTR_FATTR_SPACE_USED \
-		| NFS_ATTR_FATTR_CHANGE)
+		| NFS_ATTR_FATTR_SPACE_USED)
 
 /*
  * Info on the file system