fs: add helper to use mount option as path or fd

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

Link: https://lore.kernel.org/r/20241014-work-overlayfs-v3-1-32b3fed1286e@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index 24727ec34e5aa434364e87879cccf9fe1ec19d37..8f583b814e6e4377cf0611c11abbf24168a58d74 100644 (file)
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -308,6 +308,26 @@ 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_file_or_string(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_file_or_string);
+
 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..3cef566088fcf7e04c569acd849a785462c33f17 100644 (file)
--- 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_file_or_string;
 
 /*
  * 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_file_or_string(NAME, OPT) \
+                               __fsparam(fs_param_is_file_or_string, 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)