bitops: add xor_unlock_is_negative_byte()

Replace clear_bit_and_unlock_is_negative_byte() with
xor_unlock_is_negative_byte().  We have a few places that like to lock a
folio, set a flag and unlock it again.  Allow for the possibility of
combining the latter two operations for efficiency.  We are guaranteed
that the caller holds the lock, so it is safe to unlock it with the xor. 
The caller must guarantee that nobody else will set the flag without
holding the lock; it is not safe to do this with the PG_dirty flag, for
example.

Link: https://lkml.kernel.org/r/20231004165317.1061855-8-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>

1 files changed, 5 insertions, 16 deletions

diff --git a/include/asm-generic/bitops/lock.h b/include/asm-generic/bitops/lock.h
index 40913516e654..6a638e89d130 100644
--- a/include/asm-generic/bitops/lock.h
+++ b/include/asm-generic/bitops/lock.h
@@ -66,27 +66,16 @@ arch___clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
 	raw_atomic_long_set_release((atomic_long_t *)p, old);
 }
 
-/**
- * arch_clear_bit_unlock_is_negative_byte - Clear a bit in memory and test if bottom
- *                                          byte is negative, for unlock.
- * @nr: the bit to clear
- * @addr: the address to start counting from
- *
- * This is a bit of a one-trick-pony for the filemap code, which clears
- * PG_locked and tests PG_waiters,
- */
-#ifndef arch_clear_bit_unlock_is_negative_byte
-static inline bool arch_clear_bit_unlock_is_negative_byte(unsigned int nr,
-							  volatile unsigned long *p)
+#ifndef arch_xor_unlock_is_negative_byte
+static inline bool arch_xor_unlock_is_negative_byte(unsigned long mask,
+		volatile unsigned long *p)
 {
 	long old;
-	unsigned long mask = BIT_MASK(nr);
 
-	p += BIT_WORD(nr);
-	old = raw_atomic_long_fetch_andnot_release(mask, (atomic_long_t *)p);
+	old = raw_atomic_long_fetch_xor_release(mask, (atomic_long_t *)p);
 	return !!(old & BIT(7));
 }
-#define arch_clear_bit_unlock_is_negative_byte arch_clear_bit_unlock_is_negative_byte
+#define arch_xor_unlock_is_negative_byte arch_xor_unlock_is_negative_byte
 #endif
 
 #include <asm-generic/bitops/instrumented-lock.h>