[04/11] cifs: add witness mount option and data structs

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 8111d0109a2e..c2bbc444b463 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -637,6 +637,11 @@  cifs_show_options(struct seq_file *s, struct dentry *root)
 		seq_printf(s, ",multichannel,max_channels=%zu",
 			   tcon->ses->chan_max);
 
+#ifdef CONFIG_CIFS_SWN_UPCALL
+	if (tcon->use_witness)
+		seq_puts(s, ",witness");
+#endif
+
 	return 0;
 }
 
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index b6925aeeb621..5ca3a5568ac5 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -615,6 +615,7 @@  struct smb_vol {
 	unsigned int max_channels;
 	__u16 compression; /* compression algorithm 0xFFFF default 0=disabled */
 	bool rootfs:1; /* if it's a SMB root file system */
+	bool witness:1; /* use witness protocol */
 };
 
 /**
@@ -1173,6 +1174,9 @@  struct cifs_tcon {
 	int remap:2;
 	struct list_head ulist; /* cache update list */
 #endif
+#ifdef CONFIG_CIFS_SWN_UPCALL
+	bool use_witness:1; /* use witness protocol */
+#endif
 };
 
 /*
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 5aadc4632097..ed749e978ad8 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -102,7 +102,7 @@  enum {
 	Opt_resilient, Opt_noresilient,
 	Opt_domainauto, Opt_rdma, Opt_modesid, Opt_rootfs,
 	Opt_multichannel, Opt_nomultichannel,
-	Opt_compress,
+	Opt_compress, Opt_witness,
 
 	/* Mount options which take numeric value */
 	Opt_backupuid, Opt_backupgid, Opt_uid,
@@ -276,6 +276,7 @@  static const match_table_t cifs_mount_option_tokens = {
 	{ Opt_ignore, "relatime" },
 	{ Opt_ignore, "_netdev" },
 	{ Opt_rootfs, "rootfs" },
+	{ Opt_witness, "witness" },
 
 	{ Opt_err, NULL }
 };
@@ -1538,6 +1539,13 @@  cifs_parse_mount_options(const char *mountdata, const char *devname,
 			vol->rootfs = true;
 #endif
 			break;
+		case Opt_witness:
+#ifndef CONFIG_CIFS_SWN_UPCALL
+			cifs_dbg(VFS, "Witness support needs CONFIG_CIFS_SWN_UPCALL kernel config option set\n");
+			goto cifs_parse_mount_err;
+#endif
+			vol->witness = true;
+			break;
 		case Opt_posixpaths:
 			vol->posix_paths = 1;
 			break;
@@ -3158,6 +3166,8 @@  cifs_put_tcon(struct cifs_tcon *tcon)
 		return;
 	}
 
+	/* TODO witness unregister */
+
 	list_del_init(&tcon->tcon_list);
 	spin_unlock(&cifs_tcp_ses_lock);
 
@@ -3319,6 +3329,26 @@  cifs_get_tcon(struct cifs_ses *ses, struct smb_vol *volume_info)
 		tcon->use_resilient = true;
 	}
 
+#ifdef CONFIG_CIFS_SWN_UPCALL
+	tcon->use_witness = false;
+	if (volume_info->witness) {
+		if (ses->server->vals->protocol_id >= SMB30_PROT_ID) {
+			if (tcon->capabilities & SMB2_SHARE_CAP_CLUSTER) {
+				/* TODO witness register */
+				tcon->use_witness = true;
+			} else {
+				cifs_dbg(VFS, "witness requested on mount but no CLUSTER capability on share\n");
+				rc = -EOPNOTSUPP;
+				goto out_fail;
+			}
+		} else {
+			cifs_dbg(VFS, "SMB3 or later required for witness option\n");
+			rc = -EOPNOTSUPP;
+			goto out_fail;
+		}
+	}
+#endif
+
 	/* If the user really knows what they are doing they can override */
 	if (tcon->share_flags & SMB2_SHAREFLAG_NO_CACHING) {
 		if (volume_info->cache_ro)
@@ -5070,6 +5100,9 @@  cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 	vol_info->sectype = master_tcon->ses->sectype;
 	vol_info->sign = master_tcon->ses->sign;
 	vol_info->seal = master_tcon->seal;
+#ifdef CONFIG_CIFS_SWN_UPCALL
+	vol_info->witness = master_tcon->use_witness;
+#endif
 
 	rc = cifs_set_vol_auth(vol_info, master_tcon->ses);
 	if (rc) {