afs: Implement client support for the YFSVL.GetCellName RPC op

Implement client support for the YFSVL.GetCellName RPC operation by which
YFS permits the canonical cell name to be queried from a VL server.

Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/afs.h

@@ -10,7 +10,7 @@
 
 #include <linux/in.h>
 
-#define AFS_MAXCELLNAME		64  	/* Maximum length of a cell name */
+#define AFS_MAXCELLNAME		256  	/* Maximum length of a cell name */
 #define AFS_MAXVOLNAME		64  	/* Maximum length of a volume name */
 #define AFS_MAXNSERVERS		8   	/* Maximum servers in a basic volume record */
 #define AFS_NMAXNSERVERS	13  	/* Maximum servers in a N/U-class volume record */

fs/afs/afs_vl.h

@@ -22,6 +22,7 @@ enum AFSVL_Operations {
 	VLGETENTRYBYNAMEU	= 527,	/* AFS Get VLDB entry by name (UUID-variant) */
 	VLGETADDRSU		= 533,	/* AFS Get addrs for fileserver */
 	YVLGETENDPOINTS		= 64002, /* YFS Get endpoints for file/volume server */
+	YVLGETCELLNAME		= 64014, /* YFS Get actual cell name */
 	VLGETCAPABILITIES	= 65537, /* AFS Get server capabilities */
 };
 

fs/afs/internal.h

@@ -116,6 +116,7 @@ struct afs_call {
 		long			ret0;	/* Value to reply with instead of 0 */
 		struct afs_addr_list	*ret_alist;
 		struct afs_vldb_entry	*ret_vldb;
+		char			*ret_str;
 	};
 	struct afs_operation	*op;
 	unsigned int		server_index;
@@ -1373,6 +1374,7 @@ extern struct afs_addr_list *afs_vl_get_addrs_u(struct afs_vl_cursor *, const uu
 extern struct afs_call *afs_vl_get_capabilities(struct afs_net *, struct afs_addr_cursor *,
 						struct key *, struct afs_vlserver *, unsigned int);
 extern struct afs_addr_list *afs_yfsvl_get_endpoints(struct afs_vl_cursor *, const uuid_t *);
+extern char *afs_yfsvl_get_cell_name(struct afs_vl_cursor *);
 
 /*
  * vl_probe.c

fs/afs/vlclient.c

@@ -645,3 +645,114 @@ struct afs_addr_list *afs_yfsvl_get_endpoints(struct afs_vl_cursor *vc,
 	afs_make_call(&vc->ac, call, GFP_KERNEL);
 	return (struct afs_addr_list *)afs_wait_for_call_to_complete(call, &vc->ac);
 }
+
+/*
+ * Deliver reply data to a YFSVL.GetCellName operation.
+ */
+static int afs_deliver_yfsvl_get_cell_name(struct afs_call *call)
+{
+	char *cell_name;
+	u32 namesz, paddedsz;
+	int ret;
+
+	_enter("{%u,%zu/%u}",
+	       call->unmarshall, iov_iter_count(call->iter), call->count);
+
+	switch (call->unmarshall) {
+	case 0:
+		afs_extract_to_tmp(call);
+		call->unmarshall++;
+
+		/* Fall through - and extract the cell name length */
+	case 1:
+		ret = afs_extract_data(call, true);
+		if (ret < 0)
+			return ret;
+
+		namesz = ntohl(call->tmp);
+		if (namesz > AFS_MAXCELLNAME)
+			return afs_protocol_error(call, afs_eproto_cellname_len);
+		paddedsz = (namesz + 3) & ~3;
+		call->count = namesz;
+		call->count2 = paddedsz - namesz;
+
+		cell_name = kmalloc(namesz + 1, GFP_KERNEL);
+		if (!cell_name)
+			return -ENOMEM;
+		cell_name[namesz] = 0;
+		call->ret_str = cell_name;
+
+		afs_extract_begin(call, cell_name, namesz);
+		call->unmarshall++;
+
+		/* Fall through - and extract cell name */
+	case 2:
+		ret = afs_extract_data(call, true);
+		if (ret < 0)
+			return ret;
+
+		afs_extract_discard(call, call->count2);
+		call->unmarshall++;
+
+		/* Fall through - and extract padding */
+	case 3:
+		ret = afs_extract_data(call, false);
+		if (ret < 0)
+			return ret;
+
+		call->unmarshall++;
+		break;
+	}
+
+	_leave(" = 0 [done]");
+	return 0;
+}
+
+static void afs_destroy_yfsvl_get_cell_name(struct afs_call *call)
+{
+	kfree(call->ret_str);
+	afs_flat_call_destructor(call);
+}
+
+/*
+ * VL.GetCapabilities operation type
+ */
+static const struct afs_call_type afs_YFSVLGetCellName = {
+	.name		= "YFSVL.GetCellName",
+	.op		= afs_YFSVL_GetCellName,
+	.deliver	= afs_deliver_yfsvl_get_cell_name,
+	.destructor	= afs_destroy_yfsvl_get_cell_name,
+};
+
+/*
+ * Probe a volume server for the capabilities that it supports.  This can
+ * return up to 196 words.
+ *
+ * We use this to probe for service upgrade to determine what the server at the
+ * other end supports.
+ */
+char *afs_yfsvl_get_cell_name(struct afs_vl_cursor *vc)
+{
+	struct afs_call *call;
+	struct afs_net *net = vc->cell->net;
+	__be32 *bp;
+
+	_enter("");
+
+	call = afs_alloc_flat_call(net, &afs_YFSVLGetCellName, 1 * 4, 0);
+	if (!call)
+		return ERR_PTR(-ENOMEM);
+
+	call->key = vc->key;
+	call->ret_str = NULL;
+	call->max_lifespan = AFS_VL_MAX_LIFESPAN;
+
+	/* marshall the parameters */
+	bp = call->request;
+	*bp++ = htonl(YVLGETCELLNAME);
+
+	/* Can't take a ref on server */
+	trace_afs_make_vl_call(call);
+	afs_make_call(&vc->ac, call, GFP_KERNEL);
+	return (char *)afs_wait_for_call_to_complete(call, &vc->ac);
+}

include/trace/events/afs.h

@@ -111,6 +111,7 @@ enum afs_vl_operation {
 	afs_VL_GetEntryByNameU	= 527,		/* AFS Get Vol Entry By Name operation ID */
 	afs_VL_GetAddrsU	= 533,		/* AFS Get FS server addresses */
 	afs_YFSVL_GetEndpoints	= 64002,	/* YFS Get FS & Vol server addresses */
+	afs_YFSVL_GetCellName	= 64014,	/* YFS Get actual cell name */
 	afs_VL_GetCapabilities	= 65537,	/* AFS Get VL server capabilities */
 };
 
@@ -143,6 +144,7 @@ enum afs_eproto_cause {
 	afs_eproto_bad_status,
 	afs_eproto_cb_count,
 	afs_eproto_cb_fid_count,
+	afs_eproto_cellname_len,
 	afs_eproto_file_type,
 	afs_eproto_ibulkst_cb_count,
 	afs_eproto_ibulkst_count,
@@ -316,6 +318,7 @@ enum afs_cb_break_reason {
 	EM(afs_VL_GetEntryByNameU,		"VL.GetEntryByNameU") \
 	EM(afs_VL_GetAddrsU,			"VL.GetAddrsU") \
 	EM(afs_YFSVL_GetEndpoints,		"YFSVL.GetEndpoints") \
+	EM(afs_YFSVL_GetCellName,		"YFSVL.GetCellName") \
 	E_(afs_VL_GetCapabilities,		"VL.GetCapabilities")
 
 #define afs_edit_dir_ops				  \
@@ -345,6 +348,7 @@ enum afs_cb_break_reason {
 	EM(afs_eproto_bad_status,	"BadStatus") \
 	EM(afs_eproto_cb_count,		"CbCount") \
 	EM(afs_eproto_cb_fid_count,	"CbFidCount") \
+	EM(afs_eproto_cellname_len,	"CellNameLen") \
 	EM(afs_eproto_file_type,	"FileTYpe") \
 	EM(afs_eproto_ibulkst_cb_count,	"IBS.CbCount") \
 	EM(afs_eproto_ibulkst_count,	"IBS.FidCount") \