ext4: mark ctx_*_flags() with __maybe_unused

When ctx_set_flags() is unused, it prevents kernel builds
with clang, `make W=1` and CONFIG_WERROR=y:

.../ext4/super.c:2120:1: error: unused function 'ctx_set_flags' [-Werror,-Wunused-function]
 2120 | EXT4_SET_CTX(flags); /* set only */
      | ^~~~~~~~~~~~~~~~~~~

Fix this by marking ctx_*_flags() with __maybe_unused
(mark both for the sake of symmetry).

See also commit 6863f56 ("kbuild: allow Clang to find unused static
inline functions for W=1 build").

Signed-off-by: Andy Shevchenko <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>

Author: andy-shev

fs/ext4/super.c

@@ -2096,16 +2096,16 @@ static int ext4_parse_test_dummy_encryption(const struct fs_parameter *param,
 }
 
 #define EXT4_SET_CTX(name)						\
-static inline void ctx_set_##name(struct ext4_fs_context *ctx,		\
-				  unsigned long flag)			\
+static inline __maybe_unused						\
+void ctx_set_##name(struct ext4_fs_context *ctx, unsigned long flag)	\
 {									\
 	ctx->mask_s_##name |= flag;					\
 	ctx->vals_s_##name |= flag;					\
 }
 
 #define EXT4_CLEAR_CTX(name)						\
-static inline void ctx_clear_##name(struct ext4_fs_context *ctx,	\
-				    unsigned long flag)			\
+static inline __maybe_unused						\
+void ctx_clear_##name(struct ext4_fs_context *ctx, unsigned long flag)	\
 {									\
 	ctx->mask_s_##name |= flag;					\
 	ctx->vals_s_##name &= ~flag;					\