linux-kernel - [PATCH v2 1/8] lib/find_bit.c: Add find_last_zero

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Date:   Sun, 6 Dec 2020 15:46:24 +0900
From:   Levi Yun <ppbuk5246@...il.com>
To:     akpm@...ux-foundation.org, yury.norov@...il.com,
        andriy.shevchenko@...ux.intel.com,
        richard.weiyang@...ux.alibaba.com, christian.brauner@...ntu.com,
        arnd@...db.de, jpoimboe@...hat.com, changbin.du@...el.com,
        rdunlap@...radead.org, masahiroy@...nel.org,
        gregkh@...uxfoundation.org, peterz@...radead.org,
        peter.enderborg@...y.com, krzk@...nel.org,
        brendanhiggins@...gle.com, keescook@...omium.org,
        broonie@...nel.org, matti.vaittinen@...rohmeurope.com,
        mhiramat@...nel.org, jpa@....mail.kapsi.fi, nivedita@...m.mit.edu,
        glider@...gle.com, orson.zhai@...soc.com,
        takahiro.akashi@...aro.org, clm@...com, josef@...icpanda.com,
        dsterba@...e.com, dushistov@...l.ru
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-btrfs@...r.kernel.org
Subject: [PATCH v2 1/8] lib/find_bit.c: Add find_last_zero_bit

Inspired find_next_*_bit and find_last_bit, add find_last_zero_bit
And add le support about find_last_bit and find_last_zero_bit.

Signed-off-by: Levi Yun <ppbuk5246@...il.com>
---
 lib/find_bit.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 62 insertions(+), 2 deletions(-)

diff --git a/lib/find_bit.c b/lib/find_bit.c
index 4a8751010d59..f9dda2bf7fa9 100644
--- a/lib/find_bit.c
+++ b/lib/find_bit.c
@@ -90,7 +90,7 @@ unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
 EXPORT_SYMBOL(find_next_zero_bit);
 #endif
 
-#if !defined(find_next_and_bit)
+#ifndef find_next_and_bit
 unsigned long find_next_and_bit(const unsigned long *addr1,
 		const unsigned long *addr2, unsigned long size,
 		unsigned long offset)
@@ -141,7 +141,7 @@ unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
 {
 	if (size) {
 		unsigned long val = BITMAP_LAST_WORD_MASK(size);
-		unsigned long idx = (size-1) / BITS_PER_LONG;
+		unsigned long idx = (size - 1) / BITS_PER_LONG;
 
 		do {
 			val &= addr[idx];
@@ -156,6 +156,27 @@ unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
 EXPORT_SYMBOL(find_last_bit);
 #endif
 
+#ifndef find_last_zero_bit
+unsigned long find_last_zero_bit(const unsigned long *addr, unsigned long size)
+{
+	if (size) {
+		unsigned long val = BITMAP_LAST_WORD_MASK(size);
+		unsigned long idx = (size - 1) / BITS_PER_LONG;
+
+		do {
+			val &= ~addr[idx];
+			if (val)
+				return idx * BITS_PER_LONG + __fls(val);
+
+			val = ~0ul;
+		} while (idx--);
+	}
+
+	return size;
+}
+EXPORT_SYMBOL(find_last_zero_bit);
+#endif
+
 #ifdef __BIG_ENDIAN
 
 #ifndef find_next_zero_bit_le
@@ -176,6 +197,45 @@ unsigned long find_next_bit_le(const void *addr, unsigned
 EXPORT_SYMBOL(find_next_bit_le);
 #endif
 
+static unsigned long _find_last_bit_le(const unsigned long *addr,
+		unsigned long size, unsigned long invert)
+{
+	if (size) {
+		unsigned long val = BITMAP_LAST_WORD_MASK(size);
+		unsigned long tmp;
+		unsigned long idx = (size - 1) / BITS_PER_LONG;
+
+	val = swab(val);
+
+		do {
+			tmp = swab(addr[idx]);
+			tmp ^= invert;
+			val &= tmp;
+			if (val)
+				return idx * BITS_PER_LONG + __fls(val);
+
+			val = ~0ul;
+		} while (idx--);
+	}
+	return size;
+}
+
+#ifndef find_last_zero_bit_le
+unsigned long find_last_zero_bit_le(const unsigned void *addr, unsigned long size)
+{
+	return _find_last_bit_le(addr, size, ~0UL);
+}
+EXPORT_SYMBOL(find_last_zero_bit_le);
+#endif
+
+#ifdef find_last_bit_le
+unsigned long find_last_bit_le(const unsigned void *addr, unsigned long size)
+{
+	return _find_last_bit_le(addr, size, 0UL);
+}
+EXPORT_SYMBOL(find_last_bit_le);
+#endif
+
 #endif /* __BIG_ENDIAN */
 
 unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
-- 
2.27.0