[PATCH RFC v2 1/4] fs: add helper to use mount option as path or fd

[Christian Brauner <brauner@kernel.org>]

Allow filesystems to use a mount option either as a
path or a file descriptor.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/fs_parser.c            | 19 +++++++++++++++++++
 include/linux/fs_parser.h |  5 ++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index 24727ec34e5aa434364e87879cccf9fe1ec19d37..a017415d8d6bc91608ece5d42fa4bea26e47456b 100644
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -308,6 +308,25 @@ int fs_param_is_fd(struct p_log *log, const struct fs_parameter_spec *p,
 }
 EXPORT_SYMBOL(fs_param_is_fd);
 
+int fs_param_is_fd_or_path(struct p_log *log, const struct fs_parameter_spec *p,
+			   struct fs_parameter *param,
+			   struct fs_parse_result *result)
+{
+	switch (param->type) {
+	case fs_value_is_string:
+		return fs_param_is_string(log, p, param, result);
+	case fs_value_is_file:
+		result->uint_32 = param->dirfd;
+		if (result->uint_32 <= INT_MAX)
+			return 0;
+		break;
+	default:
+		break;
+	}
+	return fs_param_bad_value(log, param);
+}
+EXPORT_SYMBOL(fs_param_is_fd_or_path);
+
 int fs_param_is_uid(struct p_log *log, const struct fs_parameter_spec *p,
 		    struct fs_parameter *param, struct fs_parse_result *result)
 {
diff --git a/include/linux/fs_parser.h b/include/linux/fs_parser.h
index 6cf713a7e6c6fc2402a68c87036264eaed921432..73fe4e119ee24b3bed1f0cf2bc23d6b31811cb69 100644
--- a/include/linux/fs_parser.h
+++ b/include/linux/fs_parser.h
@@ -28,7 +28,8 @@ typedef int fs_param_type(struct p_log *,
  */
 fs_param_type fs_param_is_bool, fs_param_is_u32, fs_param_is_s32, fs_param_is_u64,
 	fs_param_is_enum, fs_param_is_string, fs_param_is_blob, fs_param_is_blockdev,
-	fs_param_is_path, fs_param_is_fd, fs_param_is_uid, fs_param_is_gid;
+	fs_param_is_path, fs_param_is_fd, fs_param_is_uid, fs_param_is_gid,
+	fs_param_is_fd_or_path;
 
 /*
  * Specification of the type of value a parameter wants.
@@ -133,6 +134,8 @@ static inline bool fs_validate_description(const char *name,
 #define fsparam_bdev(NAME, OPT)	__fsparam(fs_param_is_blockdev, NAME, OPT, 0, NULL)
 #define fsparam_path(NAME, OPT)	__fsparam(fs_param_is_path, NAME, OPT, 0, NULL)
 #define fsparam_fd(NAME, OPT)	__fsparam(fs_param_is_fd, NAME, OPT, 0, NULL)
+#define fsparam_fd_or_path(NAME, OPT) \
+				__fsparam(fs_param_is_fd_or_path, NAME, OPT, 0, NULL)
 #define fsparam_uid(NAME, OPT) __fsparam(fs_param_is_uid, NAME, OPT, 0, NULL)
 #define fsparam_gid(NAME, OPT) __fsparam(fs_param_is_gid, NAME, OPT, 0, NULL)
 

-- 
2.45.2