diff --git a/fs/afs/fs_probe.c b/fs/afs/fs_probe.c
index e7e98ad63a91..c0031a3ab42f 100644
--- a/fs/afs/fs_probe.c
+++ b/fs/afs/fs_probe.c
@@ -9,6 +9,7 @@
 #include <linux/slab.h>
 #include "afs_fs.h"
 #include "internal.h"
+#include "protocol_afs.h"
 #include "protocol_yfs.h"
 
 static unsigned int afs_fs_probe_fast_poll_interval = 30 * HZ;
@@ -102,7 +103,7 @@ void afs_fileserver_probe_result(struct afs_call *call)
 	struct afs_addr_list *alist = call->alist;
 	struct afs_server *server = call->server;
 	unsigned int index = call->addr_ix;
-	unsigned int rtt_us = 0;
+	unsigned int rtt_us = 0, cap0;
 	int ret = call->error;
 
 	_enter("%pU,%u", &server->uuid, index);
@@ -159,6 +160,11 @@ responded:
 			clear_bit(AFS_SERVER_FL_IS_YFS, &server->flags);
 			alist->addrs[index].srx_service = call->service_id;
 		}
+		cap0 = ntohl(call->tmp);
+		if (cap0 & AFS3_VICED_CAPABILITY_64BITFILES)
+			set_bit(AFS_SERVER_FL_HAS_FS64, &server->flags);
+		else
+			clear_bit(AFS_SERVER_FL_HAS_FS64, &server->flags);
 	}
 
 	if (rxrpc_kernel_get_srtt(call->net->socket, call->rxcall, &rtt_us) &&
diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index dd3f45d906d2..4943413d9c5f 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -456,9 +456,7 @@ void afs_fs_fetch_data(struct afs_operation *op)
 	struct afs_read *req = op->fetch.req;
 	__be32 *bp;
 
-	if (upper_32_bits(req->pos) ||
-	    upper_32_bits(req->len) ||
-	    upper_32_bits(req->pos + req->len))
+	if (test_bit(AFS_SERVER_FL_HAS_FS64, &op->server->flags))
 		return afs_fs_fetch_data64(op);
 
 	_enter("");
@@ -1113,9 +1111,7 @@ void afs_fs_store_data(struct afs_operation *op)
 	       (unsigned long long)op->store.pos,
 	       (unsigned long long)op->store.i_size);
 
-	if (upper_32_bits(op->store.pos) ||
-	    upper_32_bits(op->store.size) ||
-	    upper_32_bits(op->store.i_size))
+	if (test_bit(AFS_SERVER_FL_HAS_FS64, &op->server->flags))
 		return afs_fs_store_data64(op);
 
 	call = afs_alloc_flat_call(op->net, &afs_RXFSStoreData,
@@ -1229,7 +1225,7 @@ static void afs_fs_setattr_size(struct afs_operation *op)
 	       key_serial(op->key), vp->fid.vid, vp->fid.vnode);
 
 	ASSERT(attr->ia_valid & ATTR_SIZE);
-	if (upper_32_bits(attr->ia_size))
+	if (test_bit(AFS_SERVER_FL_HAS_FS64, &op->server->flags))
 		return afs_fs_setattr_size64(op);
 
 	call = afs_alloc_flat_call(op->net, &afs_RXFSStoreData_as_Status,
@@ -1657,20 +1653,33 @@ static int afs_deliver_fs_get_capabilities(struct afs_call *call)
 			return ret;
 
 		count = ntohl(call->tmp);
-
 		call->count = count;
 		call->count2 = count;
-		afs_extract_discard(call, count * sizeof(__be32));
+		if (count == 0) {
+			call->unmarshall = 4;
+			call->tmp = 0;
+			break;
+		}
+
+		/* Extract the first word of the capabilities to call->tmp */
+		afs_extract_to_tmp(call);
 		call->unmarshall++;
 		fallthrough;
 
-		/* Extract capabilities words */
 	case 2:
 		ret = afs_extract_data(call, false);
 		if (ret < 0)
 			return ret;
 
-		/* TODO: Examine capabilities */
+		afs_extract_discard(call, (count - 1) * sizeof(__be32));
+		call->unmarshall++;
+		fallthrough;
+
+		/* Extract remaining capabilities words */
+	case 3:
+		ret = afs_extract_data(call, false);
+		if (ret < 0)
+			return ret;
 
 		call->unmarshall++;
 		break;
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index c97618855b46..b0fe27ae60db 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -520,6 +520,7 @@ struct afs_server {
 #define AFS_SERVER_FL_IS_YFS	16		/* Server is YFS not AFS */
 #define AFS_SERVER_FL_NO_IBULK	17		/* Fileserver doesn't support FS.InlineBulkStatus */
 #define AFS_SERVER_FL_NO_RM2	18		/* Fileserver doesn't support YFS.RemoveFile2 */
+#define AFS_SERVER_FL_HAS_FS64	19		/* Fileserver supports FS.{Fetch,Store}Data64 */
 	atomic_t		ref;		/* Object refcount */
 	atomic_t		active;		/* Active user count */
 	u32			addr_version;	/* Address list version */
diff --git a/fs/afs/protocol_afs.h b/fs/afs/protocol_afs.h
new file mode 100644
index 000000000000..0c39358c8b70
--- /dev/null
+++ b/fs/afs/protocol_afs.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* AFS protocol bits
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+
+#define AFSCAPABILITIESMAX 196 /* Maximum number of words in a capability set */
+
+/* AFS3 Fileserver capabilities word 0 */
+#define AFS3_VICED_CAPABILITY_ERRORTRANS	0x0001 /* Uses UAE errors */
+#define AFS3_VICED_CAPABILITY_64BITFILES	0x0002 /* FetchData64 & StoreData64 supported */
+#define AFS3_VICED_CAPABILITY_WRITELOCKACL	0x0004 /* Can lock a file even without lock perm */
+#define AFS3_VICED_CAPABILITY_SANEACLS		0x0008 /* ACLs reviewed for sanity - don't use */
diff --git a/fs/afs/protocol_yfs.h b/fs/afs/protocol_yfs.h
index b5bd03b1d3c7..e4cd89c44c46 100644
--- a/fs/afs/protocol_yfs.h
+++ b/fs/afs/protocol_yfs.h
@@ -168,3 +168,9 @@ enum yfs_lock_type {
 	yfs_LockMandatoryWrite	= 0x101,
 	yfs_LockMandatoryExtend	= 0x102,
 };
+
+/* RXYFS Viced Capability Flags */
+#define YFS_VICED_CAPABILITY_ERRORTRANS		0x0001 /* Deprecated v0.195 */
+#define YFS_VICED_CAPABILITY_64BITFILES		0x0002 /* Deprecated v0.195 */
+#define YFS_VICED_CAPABILITY_WRITELOCKACL	0x0004 /* Can lock a file even without lock perm */
+#define YFS_VICED_CAPABILITY_SANEACLS		0x0008 /* Deprecated v0.195 */