bcachefs: Mark bch_errcode helpers __attribute__((const))

These don't access global memory or defer pointer arguments - this
enables CSE optimizations.

Signed-off-by: Kent Overstreet <[email protected]>

Author: Kent Overstreet

fs/bcachefs/errcode.c

@@ -13,12 +13,13 @@ static const char * const bch2_errcode_strs[] = {
 	NULL
 };
 
-static unsigned bch2_errcode_parents[] = {
+static const unsigned bch2_errcode_parents[] = {
 #define x(class, err) [BCH_ERR_##err - BCH_ERR_START] = class,
 	BCH_ERRCODES()
 #undef x
 };
 
+__attribute__((const))
 const char *bch2_err_str(int err)
 {
 	const char *errstr;
@@ -36,6 +37,7 @@ const char *bch2_err_str(int err)
 	return errstr ?: "(Invalid error)";
 }
 
+__attribute__((const))
 bool __bch2_err_matches(int err, int class)
 {
 	err	= abs(err);

fs/bcachefs/errcode.h

@@ -357,9 +357,11 @@ enum bch_errcode {
 	BCH_ERR_MAX
 };
 
-const char *bch2_err_str(int);
-bool __bch2_err_matches(int, int);
+__attribute__((const)) const char *bch2_err_str(int);
 
+__attribute__((const)) bool __bch2_err_matches(int, int);
+
+__attribute__((const))
 static inline bool _bch2_err_matches(int err, int class)
 {
 	return err < 0 && __bch2_err_matches(err, class);