cifs: Add mount option -o reparse=none

This new mount option allows to completely disable creating new reparse
points. When -o sfu or -o mfsymlinks or -o symlink= is not specified then
creating any special file (fifo, socket, symlink, block and char) will fail
with -EOPNOTSUPP error.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: pali

fs/smb/client/cifsglob.h

@@ -160,6 +160,7 @@ enum upcall_target_enum {
 };
 
 enum cifs_reparse_type {
+	CIFS_REPARSE_TYPE_NONE,
 	CIFS_REPARSE_TYPE_NFS,
 	CIFS_REPARSE_TYPE_WSL,
 	CIFS_REPARSE_TYPE_DEFAULT = CIFS_REPARSE_TYPE_NFS,
@@ -168,6 +169,8 @@ enum cifs_reparse_type {
 static inline const char *cifs_reparse_type_str(enum cifs_reparse_type type)
 {
 	switch (type) {
+	case CIFS_REPARSE_TYPE_NONE:
+		return "none";
 	case CIFS_REPARSE_TYPE_NFS:
 		return "nfs";
 	case CIFS_REPARSE_TYPE_WSL:

fs/smb/client/fs_context.c

@@ -334,6 +334,7 @@ cifs_parse_cache_flavor(struct fs_context *fc, char *value, struct smb3_fs_conte
 
 static const match_table_t reparse_flavor_tokens = {
 	{ Opt_reparse_default,	"default" },
+	{ Opt_reparse_none,	"none" },
 	{ Opt_reparse_nfs,	"nfs" },
 	{ Opt_reparse_wsl,	"wsl" },
 	{ Opt_reparse_err,	NULL },
@@ -348,6 +349,9 @@ static int parse_reparse_flavor(struct fs_context *fc, char *value,
 	case Opt_reparse_default:
 		ctx->reparse_type = CIFS_REPARSE_TYPE_DEFAULT;
 		break;
+	case Opt_reparse_none:
+		ctx->reparse_type = CIFS_REPARSE_TYPE_NONE;
+		break;
 	case Opt_reparse_nfs:
 		ctx->reparse_type = CIFS_REPARSE_TYPE_NFS;
 		break;
@@ -1828,8 +1832,10 @@ enum cifs_symlink_type get_cifs_symlink_type(struct cifs_sb_info *cifs_sb)
 			return CIFS_SYMLINK_TYPE_SFU;
 		else if (cifs_sb->ctx->linux_ext && !cifs_sb->ctx->no_linux_ext)
 			return CIFS_SYMLINK_TYPE_UNIX;
-		else
+		else if (cifs_sb->ctx->reparse_type != CIFS_REPARSE_TYPE_NONE)
 			return CIFS_SYMLINK_TYPE_NATIVE;
+		else
+			return CIFS_SYMLINK_TYPE_NONE;
 	} else {
 		return cifs_sb->ctx->symlink_type;
 	}

fs/smb/client/fs_context.h

@@ -43,6 +43,7 @@ enum {
 
 enum cifs_reparse_parm {
 	Opt_reparse_default,
+	Opt_reparse_none,
 	Opt_reparse_nfs,
 	Opt_reparse_wsl,
 	Opt_reparse_err