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diff --git a/sys/compat/linuxkpi/common/include/linux/log2.h b/sys/compat/linuxkpi/common/include/linux/log2.h
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+/*-
+ * Copyright (c) 2010 Isilon Systems, Inc.
+ * Copyright (c) 2010 iX Systems, Inc.
+ * Copyright (c) 2010 Panasas, Inc.
+ * Copyright (c) 2013-2015 Mellanox Technologies, Ltd.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice unmodified, this list of conditions, and the following
+ * disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+#ifndef _LINUX_LOG2_H_
+#define _LINUX_LOG2_H_
+
+#include <linux/types.h>
+
+#include <sys/libkern.h>
+
+static inline unsigned long
+roundup_pow_of_two(unsigned long x)
+{
+ return (1UL << flsl(x - 1));
+}
+
+static inline int
+is_power_of_2(unsigned long n)
+{
+ return (n == roundup_pow_of_two(n));
+}
+
+static inline unsigned long
+rounddown_pow_of_two(unsigned long x)
+{
+ return (1UL << (flsl(x) - 1));
+}
+
+#define ilog2(n) \
+( \
+ __builtin_constant_p(n) ? ( \
+ (n) < 1 ? -1 : \
+ (n) & (1ULL << 63) ? 63 : \
+ (n) & (1ULL << 62) ? 62 : \
+ (n) & (1ULL << 61) ? 61 : \
+ (n) & (1ULL << 60) ? 60 : \
+ (n) & (1ULL << 59) ? 59 : \
+ (n) & (1ULL << 58) ? 58 : \
+ (n) & (1ULL << 57) ? 57 : \
+ (n) & (1ULL << 56) ? 56 : \
+ (n) & (1ULL << 55) ? 55 : \
+ (n) & (1ULL << 54) ? 54 : \
+ (n) & (1ULL << 53) ? 53 : \
+ (n) & (1ULL << 52) ? 52 : \
+ (n) & (1ULL << 51) ? 51 : \
+ (n) & (1ULL << 50) ? 50 : \
+ (n) & (1ULL << 49) ? 49 : \
+ (n) & (1ULL << 48) ? 48 : \
+ (n) & (1ULL << 47) ? 47 : \
+ (n) & (1ULL << 46) ? 46 : \
+ (n) & (1ULL << 45) ? 45 : \
+ (n) & (1ULL << 44) ? 44 : \
+ (n) & (1ULL << 43) ? 43 : \
+ (n) & (1ULL << 42) ? 42 : \
+ (n) & (1ULL << 41) ? 41 : \
+ (n) & (1ULL << 40) ? 40 : \
+ (n) & (1ULL << 39) ? 39 : \
+ (n) & (1ULL << 38) ? 38 : \
+ (n) & (1ULL << 37) ? 37 : \
+ (n) & (1ULL << 36) ? 36 : \
+ (n) & (1ULL << 35) ? 35 : \
+ (n) & (1ULL << 34) ? 34 : \
+ (n) & (1ULL << 33) ? 33 : \
+ (n) & (1ULL << 32) ? 32 : \
+ (n) & (1ULL << 31) ? 31 : \
+ (n) & (1ULL << 30) ? 30 : \
+ (n) & (1ULL << 29) ? 29 : \
+ (n) & (1ULL << 28) ? 28 : \
+ (n) & (1ULL << 27) ? 27 : \
+ (n) & (1ULL << 26) ? 26 : \
+ (n) & (1ULL << 25) ? 25 : \
+ (n) & (1ULL << 24) ? 24 : \
+ (n) & (1ULL << 23) ? 23 : \
+ (n) & (1ULL << 22) ? 22 : \
+ (n) & (1ULL << 21) ? 21 : \
+ (n) & (1ULL << 20) ? 20 : \
+ (n) & (1ULL << 19) ? 19 : \
+ (n) & (1ULL << 18) ? 18 : \
+ (n) & (1ULL << 17) ? 17 : \
+ (n) & (1ULL << 16) ? 16 : \
+ (n) & (1ULL << 15) ? 15 : \
+ (n) & (1ULL << 14) ? 14 : \
+ (n) & (1ULL << 13) ? 13 : \
+ (n) & (1ULL << 12) ? 12 : \
+ (n) & (1ULL << 11) ? 11 : \
+ (n) & (1ULL << 10) ? 10 : \
+ (n) & (1ULL << 9) ? 9 : \
+ (n) & (1ULL << 8) ? 8 : \
+ (n) & (1ULL << 7) ? 7 : \
+ (n) & (1ULL << 6) ? 6 : \
+ (n) & (1ULL << 5) ? 5 : \
+ (n) & (1ULL << 4) ? 4 : \
+ (n) & (1ULL << 3) ? 3 : \
+ (n) & (1ULL << 2) ? 2 : \
+ (n) & (1ULL << 1) ? 1 : \
+ (n) & (1ULL << 0) ? 0 : \
+ -1) : \
+ (sizeof(n) <= 4) ? \
+ fls((u32)(n)) - 1 : flsll((u64)(n)) - 1 \
+)
+
+#define order_base_2(x) ilog2(roundup_pow_of_two(x))
+
+#endif /* _LINUX_LOG2_H_ */