linux-kernel - [PATCH RESEND 4/8] arch: remove GENERIC_FIND_FIRST

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Date:   Sat, 12 Jun 2021 05:36:35 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Brian Cain <bcain@...eaurora.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Rich Felker <dalias@...c.org>,
        David Hildenbrand <david@...hat.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Lobakin <alobakin@...me>,
        Samuel Mendoza-Jonas <sam@...dozajonas.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Alexey Klimov <aklimov@...hat.com>,
        Ingo Molnar <mingo@...hat.com>
Cc:     Yury Norov <yury.norov@...il.com>
Subject: [PATCH RESEND 4/8] arch: remove GENERIC_FIND_FIRST_BIT entirely

In 5.12 cycle we enabled GENERIC_FIND_FIRST_BIT config option for ARM64
and MIPS. It increased performance and shrunk .text size; and so far
I didn't receive any negative feedback on the change.

https://lore.kernel.org/linux-arch/20210225135700.1381396-1-yury.norov@gmail.com/

Now I think it's a good time to switch all architectures to use
find_{first,last}_bit() unconditionally, and so remove corresponding
config option.

The patch does't introduce functioal changes for arc, arm, arm64, mips,
m68k, s390 and x86, for other architectures I expect improvement both in
performance and .text size.

Tested-by: Alexander Lobakin <alobakin@...me> (mips)
Reviewed-by: Alexander Lobakin <alobakin@...me> (mips)
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Acked-by: Will Deacon <will@...nel.org>
Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 arch/arc/Kconfig     |  1 -
 arch/arm64/Kconfig   |  1 -
 arch/mips/Kconfig    |  1 -
 arch/s390/Kconfig    |  1 -
 arch/x86/Kconfig     |  1 -
 arch/x86/um/Kconfig  |  1 -
 include/linux/find.h | 13 -------------
 lib/Kconfig          |  3 ---
 8 files changed, 22 deletions(-)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 2d98501c0897..aa1ce528ae23 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -20,7 +20,6 @@ config ARC
 	select COMMON_CLK
 	select DMA_DIRECT_REMAP
 	select GENERIC_ATOMIC64 if !ISA_ARCV2 || !(ARC_HAS_LL64 && ARC_HAS_LLSC)
-	select GENERIC_FIND_FIRST_BIT
 	# for now, we don't need GENERIC_IRQ_PROBE, CONFIG_GENERIC_IRQ_CHIP
 	select GENERIC_IRQ_SHOW
 	select GENERIC_PCI_IOMAP
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7c17f03e99a1..207e6fce26d0 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -118,7 +118,6 @@ config ARM64
 	select GENERIC_CPU_AUTOPROBE
 	select GENERIC_CPU_VULNERABILITIES
 	select GENERIC_EARLY_IOREMAP
-	select GENERIC_FIND_FIRST_BIT
 	select GENERIC_IDLE_POLL_SETUP
 	select GENERIC_IRQ_IPI
 	select GENERIC_IRQ_PROBE
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index ef5dd91e83b4..5d5adf63005b 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -30,7 +30,6 @@ config MIPS
 	select GENERIC_ATOMIC64 if !64BIT
 	select GENERIC_CMOS_UPDATE
 	select GENERIC_CPU_AUTOPROBE
-	select GENERIC_FIND_FIRST_BIT
 	select GENERIC_GETTIMEOFDAY
 	select GENERIC_IOMAP
 	select GENERIC_IRQ_PROBE
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 8de7b3150e93..996cee2b7a3d 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -125,7 +125,6 @@ config S390
 	select GENERIC_CPU_AUTOPROBE
 	select GENERIC_CPU_VULNERABILITIES
 	select GENERIC_ENTRY
-	select GENERIC_FIND_FIRST_BIT
 	select GENERIC_GETTIMEOFDAY
 	select GENERIC_PTDUMP
 	select GENERIC_SMP_IDLE_THREAD
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 39175aa072e2..fd6bbbdc2f7d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -133,7 +133,6 @@ config X86
 	select GENERIC_CPU_VULNERABILITIES
 	select GENERIC_EARLY_IOREMAP
 	select GENERIC_ENTRY
-	select GENERIC_FIND_FIRST_BIT
 	select GENERIC_IOMAP
 	select GENERIC_IRQ_EFFECTIVE_AFF_MASK	if SMP
 	select GENERIC_IRQ_MATRIX_ALLOCATOR	if X86_LOCAL_APIC
diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig
index 95d26a69088b..40d6a06e41c8 100644
--- a/arch/x86/um/Kconfig
+++ b/arch/x86/um/Kconfig
@@ -8,7 +8,6 @@ endmenu
 
 config UML_X86
 	def_bool y
-	select GENERIC_FIND_FIRST_BIT
 
 config 64BIT
 	bool "64-bit kernel" if "$(SUBARCH)" = "x86"
diff --git a/include/linux/find.h b/include/linux/find.h
index c5410c243e04..ea57f7f38c49 100644
--- a/include/linux/find.h
+++ b/include/linux/find.h
@@ -101,8 +101,6 @@ unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
 }
 #endif
 
-#ifdef CONFIG_GENERIC_FIND_FIRST_BIT
-
 #ifndef find_first_bit
 /**
  * find_first_bit - find the first set bit in a memory region
@@ -147,17 +145,6 @@ unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
 }
 #endif
 
-#else /* CONFIG_GENERIC_FIND_FIRST_BIT */
-
-#ifndef find_first_bit
-#define find_first_bit(addr, size) find_next_bit((addr), (size), 0)
-#endif
-#ifndef find_first_zero_bit
-#define find_first_zero_bit(addr, size) find_next_zero_bit((addr), (size), 0)
-#endif
-
-#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
-
 #ifndef find_last_bit
 /**
  * find_last_bit - find the last set bit in a memory region
diff --git a/lib/Kconfig b/lib/Kconfig
index ac3b30697b2b..2663c36a6220 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -59,9 +59,6 @@ config GENERIC_STRNLEN_USER
 config GENERIC_NET_UTILS
 	bool
 
-config GENERIC_FIND_FIRST_BIT
-	bool
-
 source "lib/math/Kconfig"
 
 config NO_GENERIC_PCI_IOPORT_MAP
-- 
2.30.2