From 2a667285b53c58d72f8bdb736c040f0f36bff58a Mon Sep 17 00:00:00 2001
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Date: Wed, 4 Oct 2023 17:53:12 +0100
Subject: [PATCH] riscv: implement xor_unlock_is_negative_byte

Inspired by the riscv clear_bit_unlock(), this will surely be
more efficient than the generic one defined in filemap.c.

Link: https://lkml.kernel.org/r/20231004165317.1061855-13-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 arch/riscv/include/asm/bitops.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/riscv/include/asm/bitops.h b/arch/riscv/include/asm/bitops.h
index 3540b690944b..15e3044298a2 100644
--- a/arch/riscv/include/asm/bitops.h
+++ b/arch/riscv/include/asm/bitops.h
@@ -191,6 +191,19 @@ static inline void __clear_bit_unlock(
 	clear_bit_unlock(nr, addr);
 }
 
+static inline bool xor_unlock_is_negative_byte(unsigned long mask,
+		volatile unsigned long *addr)
+{
+	unsigned long res;
+	__asm__ __volatile__ (
+		__AMO(xor) ".rl %0, %2, %1"
+		: "=r" (res), "+A" (*addr)
+		: "r" (__NOP(mask))
+		: "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
 #undef __NOP
-- 
2.25.1