On Tue, Aug 1, 2023 at 3:22 PM <ndesaulniers@xxxxxxxxxx> wrote: > > Compiling big-endian targets with Clang produces the diagnostic: > > fs/namei.c:2173:13: warning: use of bitwise '|' with boolean operands > [-Wbitwise-instead-of-logical] > } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); > ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > || > fs/namei.c:2173:13: note: cast one or both operands to int to silence > this warning > > It appears that when has_zero was introduced, two definitions were > produced with different signatures (in particular different return types). > > Looking at the usage in hash_name() in fs/namei.c, I suspect that > has_zero() is meant to be invoked twice per while loop iteration; using > logical-or would not update `bdata` when `a` did not have zeros. So I > think it's preferred to always return an unsigned long rather than a > bool then update the while loop in hash_name() to use a logical-or s/then/than/ > rather than bitwise-or. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1832 > Fixes: 36126f8f2ed8 ("word-at-a-time: make the interfaces truly generic") > Debugged-by: Nathan Chancellor <nathan@xxxxxxxxxx> > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > --- > include/asm-generic/word-at-a-time.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/asm-generic/word-at-a-time.h b/include/asm-generic/word-at-a-time.h > index 20c93f08c993..95a1d214108a 100644 > --- a/include/asm-generic/word-at-a-time.h > +++ b/include/asm-generic/word-at-a-time.h > @@ -38,7 +38,7 @@ static inline long find_zero(unsigned long mask) > return (mask >> 8) ? byte : byte + 1; > } > > -static inline bool has_zero(unsigned long val, unsigned long *data, const struct word_at_a_time *c) > +static inline unsigned long has_zero(unsigned long val, unsigned long *data, const struct word_at_a_time *c) > { > unsigned long rhs = val | c->low_bits; > *data = rhs; > > --- > base-commit: 18b44bc5a67275641fb26f2c54ba7eef80ac5950 > change-id: 20230801-bitwise-7812b11e5fb7 > > Best regards, > -- > Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > -- Thanks, ~Nick Desaulniers
