Support .zstd suffix only for decompression

programs/fileio.c

@@ -2555,6 +2555,9 @@ int FIO_decompressFilename(FIO_ctx_t* const fCtx, FIO_prefs_t* const prefs,
 static const char *suffixList[] = {
     ZSTD_EXTENSION,
     TZSTD_EXTENSION,
+#ifndef ZSTD_NODECOMPRESS
+    ZSTD_ALT_EXTENSION,
+#endif
 #ifdef ZSTD_GZDECOMPRESS
     GZ_EXTENSION,
     TGZ_EXTENSION,

programs/fileio.h

@@ -44,6 +44,7 @@ extern "C" {
 
 #define ZSTD_EXTENSION  ".zst"
 #define TZSTD_EXTENSION ".tzst"
+#define ZSTD_ALT_EXTENSION  ".zstd" /* allow decompression of .zstd files */
 
 #define LZ4_EXTENSION   ".lz4"
 #define TLZ4_EXTENSION  ".tlz4"