Those constants are really used internally by zstd and including
linux/zstd.h into users results in the following warnings:

In file included from fs/btrfs/zstd.c:19:
./include/linux/zstd.h:798:21: warning: ‘ZSTD_skippableHeaderSize’ defined but not used [-Wunused-const-variable=]
  798 | static const size_t ZSTD_skippableHeaderSize = 8;
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/zstd.h:796:21: warning: ‘ZSTD_frameHeaderSize_max’ defined but not used [-Wunused-const-variable=]
  796 | static const size_t ZSTD_frameHeaderSize_max = ZSTD_FRAMEHEADERSIZE_MAX;
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/zstd.h:795:21: warning: ‘ZSTD_frameHeaderSize_min’ defined but not used [-Wunused-const-variable=]
  795 | static const size_t ZSTD_frameHeaderSize_min = ZSTD_FRAMEHEADERSIZE_MIN;
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/zstd.h:794:21: warning: ‘ZSTD_frameHeaderSize_prefix’ defined but not used [-Wunused-const-variable=]
  794 | static const size_t ZSTD_frameHeaderSize_prefix = 5;

So fix those warnings by turning the constants into defines.

Signed-off-by: Nikolay Borisov <redacted>
---
 include/linux/zstd.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/zstd.h b/include/linux/zstd.h
index 249575e2485f..e87f78c9b19c 100644
--- a/include/linux/zstd.h
+++ b/include/linux/zstd.h

@@ -791,11 +791,11 @@ size_t ZSTD_DStreamOutSize(void);
 /* for static allocation */
 #define ZSTD_FRAMEHEADERSIZE_MAX 18
 #define ZSTD_FRAMEHEADERSIZE_MIN  6
-static const size_t ZSTD_frameHeaderSize_prefix = 5;
-static const size_t ZSTD_frameHeaderSize_min = ZSTD_FRAMEHEADERSIZE_MIN;
-static const size_t ZSTD_frameHeaderSize_max = ZSTD_FRAMEHEADERSIZE_MAX;
+#define ZSTD_frameHeaderSize_prefix 5
+#define ZSTD_frameHeaderSize_min ZSTD_FRAMEHEADERSIZE_MIN
+#define ZSTD_frameHeaderSize_max ZSTD_FRAMEHEADERSIZE_MAX
 /* magic number + skippable frame length */
-static const size_t ZSTD_skippableHeaderSize = 8;
+#define ZSTD_skippableHeaderSize 8
 
 
 /*-*************************************

-- 
2.25.1