mm: delete checks for xor_unlock_is_negative_byte()

Architectures which don't define their own use the one in
asm-generic/bitops/lock.h. Get rid of all the ifdefs around "maybe we
don't have it".

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Acked-by: Geert Uytterhoeven <[e-mail]>
Cc: Albert Ou <[e-mail]>
Cc: Alexander Gordeev <[e-mail]>
Cc: Andreas Dilger <[e-mail]>
Cc: Christian Borntraeger <[e-mail]>
Cc: Christophe Leroy <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Ivan Kokshaysky <[e-mail]>
Cc: Matt Turner <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Nicholas Piggin <[e-mail]>
Cc: Palmer Dabbelt <[e-mail]>
Cc: Paul Walmsley <[e-mail]>
Cc: Richard Henderson <[e-mail]>
Cc: Sven Schnelle <[e-mail]>
Cc: "Theodore Ts'o" <[e-mail]>
Cc: Thomas Bogendoerfer <[e-mail]>
Cc: Vasily Gorbik <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

arch/alpha/include/asm/bitops.h

···
 
 	return (old & BIT(7)) != 0;
 }
-#define xor_unlock_is_negative_byte xor_unlock_is_negative_byte
 
 /*
  * ffz = Find First Zero in word. Undefined if no zero exists,

arch/m68k/include/asm/bitops.h

···
 	return result;
 #endif
 }
-#define xor_unlock_is_negative_byte xor_unlock_is_negative_byte
 
 /*
  *	The true 68020 and more advanced processors support the "bfffo"

arch/mips/include/asm/bitops.h

···
 
 	return res;
 }
-#define xor_unlock_is_negative_byte xor_unlock_is_negative_byte
 
 #undef __bit_op
 #undef __test_bit_op

arch/riscv/include/asm/bitops.h

···
 		: "memory");
 	return (res & BIT(7)) != 0;
 }
-#define xor_unlock_is_negative_byte xor_unlock_is_negative_byte
 
 #undef __test_and_op_bit
 #undef __op_bit

include/asm-generic/bitops/instrumented-lock.h

···
 	return arch_test_and_set_bit_lock(nr, addr);
 }
 
-#if defined(arch_xor_unlock_is_negative_byte)
 /**
  * xor_unlock_is_negative_byte - XOR a single byte in memory and test if
  * it is negative, for unlock.
···
 	instrument_atomic_write(addr, sizeof(long));
 	return arch_xor_unlock_is_negative_byte(mask, addr);
 }
-/* Let everybody know we have it. */
-#define xor_unlock_is_negative_byte xor_unlock_is_negative_byte
-#endif
-
 #endif /* _ASM_GENERIC_BITOPS_INSTRUMENTED_LOCK_H */

include/asm-generic/bitops/lock.h

···
 	old = raw_atomic_long_fetch_xor_release(mask, (atomic_long_t *)p);
 	return !!(old & BIT(7));
 }
-#define arch_xor_unlock_is_negative_byte arch_xor_unlock_is_negative_byte
 #endif
 
 #include <asm-generic/bitops/instrumented-lock.h>

kernel/kcsan/kcsan_test.c

···
 	KCSAN_EXPECT_RW_BARRIER(spin_unlock(&test_spinlock), true);
 	KCSAN_EXPECT_RW_BARRIER(mutex_lock(&test_mutex), false);
 	KCSAN_EXPECT_RW_BARRIER(mutex_unlock(&test_mutex), true);
-
-#ifdef xor_unlock_is_negative_byte
 	KCSAN_EXPECT_READ_BARRIER(xor_unlock_is_negative_byte(1, &test_var), true);
 	KCSAN_EXPECT_WRITE_BARRIER(xor_unlock_is_negative_byte(1, &test_var), true);
 	KCSAN_EXPECT_RW_BARRIER(xor_unlock_is_negative_byte(1, &test_var), true);
-#endif
 	kcsan_nestable_atomic_end();
 }
 

kernel/kcsan/selftest.c

···
 	KCSAN_CHECK_RW_BARRIER(arch_spin_unlock(&arch_spinlock));
 	spin_lock(&test_spinlock);
 	KCSAN_CHECK_RW_BARRIER(spin_unlock(&test_spinlock));
-
-#ifdef xor_unlock_is_negative_byte
 	KCSAN_CHECK_RW_BARRIER(xor_unlock_is_negative_byte(1, &test_var));
 	KCSAN_CHECK_READ_BARRIER(xor_unlock_is_negative_byte(1, &test_var));
 	KCSAN_CHECK_WRITE_BARRIER(xor_unlock_is_negative_byte(1, &test_var));
-#endif
 	kcsan_nestable_atomic_end();
 
 	return ret;

mm/filemap.c

···
 }
 EXPORT_SYMBOL_GPL(folio_add_wait_queue);
 
-#ifdef xor_unlock_is_negative_byte
-#define clear_bit_unlock_is_negative_byte(nr, p)	\
-	xor_unlock_is_negative_byte(1 << nr, p)
-#endif
-
-#ifndef clear_bit_unlock_is_negative_byte
-
-/*
- * PG_waiters is the high bit in the same byte as PG_lock.
- *
- * On x86 (and on many other architectures), we can clear PG_lock and
- * test the sign bit at the same time. But if the architecture does
- * not support that special operation, we just do this all by hand
- * instead.
- *
- * The read of PG_waiters has to be after (or concurrently with) PG_locked
- * being cleared, but a memory barrier should be unnecessary since it is
- * in the same byte as PG_locked.
- */
-static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
-{
-	clear_bit_unlock(nr, mem);
-	/* smp_mb__after_atomic(); */
-	return test_bit(PG_waiters, mem);
-}
-
-#endif
-
 /**
  * folio_unlock - Unlock a locked folio.
  * @folio: The folio.
···
 	BUILD_BUG_ON(PG_waiters != 7);
 	BUILD_BUG_ON(PG_locked > 7);
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
-	if (clear_bit_unlock_is_negative_byte(PG_locked, folio_flags(folio, 0)))
+	if (xor_unlock_is_negative_byte(1 << PG_locked, folio_flags(folio, 0)))
 		folio_wake_bit(folio, PG_locked);
 }
 EXPORT_SYMBOL(folio_unlock);

mm/kasan/kasan_test.c

···
 	KUNIT_EXPECT_KASAN_FAIL(test, test_and_change_bit(nr, addr));
 	KUNIT_EXPECT_KASAN_FAIL(test, __test_and_change_bit(nr, addr));
 	KUNIT_EXPECT_KASAN_FAIL(test, kasan_int_result = test_bit(nr, addr));
-
-#if defined(xor_unlock_is_negative_byte)
 	if (nr < 7)
 		KUNIT_EXPECT_KASAN_FAIL(test, kasan_int_result =
 				xor_unlock_is_negative_byte(1 << nr, addr));
-#endif
 }
 
 static void kasan_bitops_generic(struct kunit *test)