smb3: allow "posix" mount option to enable new SMB311 protocol extensions

If "posix" (or synonym "unix" for backward compatibility) specified on mount,
and server advertises support for SMB3.11 POSIX negotiate context, then
enable the new posix extensions on the tcon.  This can be viewed by
looking for "posix" in the mount options displayed by /proc/mounts
for that mount (ie if posix extensions allowed by server and the
experimental POSIX extensions also requested on the mount by specifying
"posix" at mount time).

Also add check to warn user if conflicting unix/nounix or posix/noposix specified
on mount.

Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/cifsfs.c

@@ -481,10 +481,20 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
 		seq_puts(s, ",persistenthandles");
 	else if (tcon->use_resilient)
 		seq_puts(s, ",resilienthandles");
+
+#ifdef CONFIG_CIFS_SMB311
+	if (tcon->posix_extensions)
+		seq_puts(s, ",posix");
+	else if (tcon->unix_ext)
+		seq_puts(s, ",unix");
+	else
+		seq_puts(s, ",nounix");
+#else
 	if (tcon->unix_ext)
 		seq_puts(s, ",unix");
 	else
 		seq_puts(s, ",nounix");
+#endif /* SMB311 */
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS)
 		seq_puts(s, ",posixpaths");
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SET_UID)

fs/cifs/cifsglob.h

@@ -522,6 +522,7 @@ struct smb_vol {
 	bool sfu_remap:1;  /* remap seven reserved chars ala SFU */
 	bool posix_paths:1; /* unset to not ask for posix pathnames. */
 	bool no_linux_ext:1;
+	bool linux_ext:1;
 	bool sfu_emul:1;
 	bool nullauth:1;   /* attempt to authenticate with null user */
 	bool nocase:1;     /* request case insensitive filenames */
@@ -960,6 +961,9 @@ struct cifs_tcon {
 	bool seal:1;      /* transport encryption for this mounted share */
 	bool unix_ext:1;  /* if false disable Linux extensions to CIFS protocol
 				for this mount even if server would support */
+#ifdef CONFIG_CIFS_SMB311
+	bool posix_extensions; /* if true SMB3.11 posix extensions enabled */
+#endif /* CIFS_311 */
 	bool local_lease:1; /* check leases (only) on local system not remote */
 	bool broken_posix_open; /* e.g. Samba server versions < 3.3.2, 3.2.9 */
 	bool broken_sparse_sup; /* if server or share does not support sparse */

fs/cifs/connect.c

@@ -77,7 +77,7 @@ enum {
 	Opt_mapposix, Opt_nomapposix,
 	Opt_mapchars, Opt_nomapchars, Opt_sfu,
 	Opt_nosfu, Opt_nodfs, Opt_posixpaths,
-	Opt_noposixpaths, Opt_nounix,
+	Opt_noposixpaths, Opt_nounix, Opt_unix,
 	Opt_nocase,
 	Opt_brl, Opt_nobrl,
 	Opt_handlecache, Opt_nohandlecache,
@@ -146,6 +146,10 @@ static const match_table_t cifs_mount_option_tokens = {
 	{ Opt_noposixpaths, "noposixpaths" },
 	{ Opt_nounix, "nounix" },
 	{ Opt_nounix, "nolinux" },
+	{ Opt_nounix, "noposix" },
+	{ Opt_unix, "unix" },
+	{ Opt_unix, "linux" },
+	{ Opt_unix, "posix" },
 	{ Opt_nocase, "nocase" },
 	{ Opt_nocase, "ignorecase" },
 	{ Opt_brl, "brl" },
@@ -1438,8 +1442,17 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 			vol->posix_paths = 0;
 			break;
 		case Opt_nounix:
+			if (vol->linux_ext)
+				cifs_dbg(VFS,
+					"conflicting unix mount options\n");
 			vol->no_linux_ext = 1;
 			break;
+		case Opt_unix:
+			if (vol->no_linux_ext)
+				cifs_dbg(VFS,
+					"conflicting unix mount options\n");
+			vol->linux_ext = 1;
+			break;
 		case Opt_nocase:
 			vol->nocase = 1;
 			break;
@@ -2985,6 +2998,13 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb_vol *volume_info)
 		}
 	}
 
+#ifdef CONFIG_CIFS_SMB311
+	if ((volume_info->linux_ext) && (ses->server->posix_ext_supported)) {
+		if (ses->server->vals->protocol_id == SMB311_PROT_ID)
+			tcon->posix_extensions = true;
+	}
+#endif /* 311 */
+
 	/*
 	 * BB Do we need to wrap session_mutex around this TCon call and Unix
 	 * SetFS as we do on SessSetup and reconnect?
@@ -4406,6 +4426,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 
 	if (cap_unix(ses))
 		reset_cifs_unix_caps(0, tcon, NULL, vol_info);
+
 out:
 	kfree(vol_info->username);
 	kzfree(vol_info->password);