linux-kernel - [PATCH 4/5] lib/find_bit: create find_first_zero_bit

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Date:   Thu, 28 Jul 2022 09:12:07 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Dennis Zhou <dennis@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Alexey Klimov <aklimov@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:     Yury Norov <yury.norov@...il.com>
Subject: [PATCH 4/5] lib/find_bit: create find_first_zero_bit_le()

find_first_zero_bit_le() is an alias to find_next_zero_bit_le(); 
despite that 'next' is known to be slower than 'first' version.

Now that we have common __find_first_bit(), it's trivial to implement
find_first_zero_bit_le() as a real function.

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 include/linux/find.h | 20 +++++++++++++++-----
 lib/find_bit.c       | 11 +++++++++++
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/include/linux/find.h b/include/linux/find.h
index 3ace995d7079..8d326d1518f4 100644
--- a/include/linux/find.h
+++ b/include/linux/find.h
@@ -19,6 +19,7 @@ unsigned long _find_next_zero_bit_le(const void *addr, unsigned
 					long size, unsigned long offset);
 unsigned long _find_next_bit_le(const void *addr, unsigned
 				long size, unsigned long offset);
+unsigned long _find_first_zero_bit_le(const unsigned long *addr, unsigned long size);
 #endif
 extern unsigned long _find_first_bit(const unsigned long *addr, unsigned long size);
 extern unsigned long _find_first_and_bit(const unsigned long *addr1,
@@ -260,6 +261,20 @@ unsigned long find_next_zero_bit_le(const void *addr, unsigned
 }
 #endif
 
+#ifndef find_first_zero_bit_le
+static inline
+unsigned long find_first_zero_bit_le(const unsigned long *addr, unsigned long size)
+{
+	if (small_const_nbits(size)) {
+		unsigned long val = swab(*addr) | ~GENMASK(size - 1, 0);
+
+		return val == ~0UL ? size : ffz(val);
+	}
+
+	return _find_first_zero_bit_le(addr, size);
+}
+#endif
+
 #ifndef find_next_bit_le
 static inline
 unsigned long find_next_bit_le(const void *addr, unsigned
@@ -279,11 +294,6 @@ unsigned long find_next_bit_le(const void *addr, unsigned
 }
 #endif
 
-#ifndef find_first_zero_bit_le
-#define find_first_zero_bit_le(addr, size) \
-	find_next_zero_bit_le((addr), (size), 0)
-#endif
-
 #else
 #error "Please fix <asm/byteorder.h>"
 #endif
diff --git a/lib/find_bit.c b/lib/find_bit.c
index d207d1699834..a56872611a59 100644
--- a/lib/find_bit.c
+++ b/lib/find_bit.c
@@ -119,6 +119,17 @@ EXPORT_SYMBOL(_find_next_zero_bit);
 #endif
 
 #ifdef __BIG_ENDIAN
+#ifndef find_first_zero_bit_le
+/*
+ * Find the first cleared bit in an LE memory region.
+ */
+unsigned long _find_first_zero_bit_le(const unsigned long *addr, unsigned long size)
+{
+	return __find_first_bit(addr, NULL, size, ~0UL, true);
+}
+EXPORT_SYMBOL(_find_first_zero_bit_le);
+#endif
+
 #ifndef find_next_zero_bit_le
 unsigned long _find_next_zero_bit_le(const void *addr, unsigned
 		long size, unsigned long offset)
-- 
2.34.1