From aa3088632a05361bc7e5dd16055f6c01f8ecbd2e Mon Sep 17 00:00:00 2001 From: Nikolay Borisov Date: Mon, 1 Oct 2018 17:46:14 +0300 Subject: [PATCH] btrfs-progs: Replace homegrown bitops related functions with kernel counterparts Replace existing find_*_bit functions with kernel equivalent. This reduces duplication, simplifies the code (we really have one worker function _find_next_bit) and is quite likely faster. No functional changes. Reviewed-by: Omar Sandoval Signed-off-by: Nikolay Borisov Signed-off-by: David Sterba --- kernel-lib/bitops.h | 142 ++++++++++++++------------------------------ 1 file changed, 46 insertions(+), 96 deletions(-) diff --git a/kernel-lib/bitops.h b/kernel-lib/bitops.h index 5b35f9fc..a9b22f24 100644 --- a/kernel-lib/bitops.h +++ b/kernel-lib/bitops.h @@ -2,6 +2,7 @@ #define _PERF_LINUX_BITOPS_H_ #include +#include "internal.h" #ifndef DIV_ROUND_UP #define DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d)) @@ -109,116 +110,65 @@ static __always_inline unsigned long __ffs(unsigned long word) #define ffz(x) __ffs(~(x)) +#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1))) +#define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1))) + /* - * Find the first set bit in a memory region. + * This is a common helper function for find_next_bit, find_next_zero_bit, and + * find_next_and_bit. The differences are: + * - The "invert" argument, which is XORed with each fetched word before + * searching it for one bits. + * - The optional "addr2", which is anded with "addr1" if present. */ -static inline unsigned long -find_first_bit(const unsigned long *addr, unsigned long size) +static inline unsigned long _find_next_bit(const unsigned long *addr1, + const unsigned long *addr2, unsigned long nbits, + unsigned long start, unsigned long invert) { - const unsigned long *p = addr; - unsigned long result = 0; unsigned long tmp; - while (size & ~(BITS_PER_LONG-1)) { - if ((tmp = *(p++))) - goto found; - result += BITS_PER_LONG; - size -= BITS_PER_LONG; - } - if (!size) - return result; + if (start >= nbits) + return nbits; - tmp = (*p) & (~0UL >> (BITS_PER_LONG - size)); - if (tmp == 0UL) /* Are any bits set? */ - return result + size; /* Nope. */ -found: - return result + __ffs(tmp); + tmp = addr1[start / BITS_PER_LONG]; + if (addr2) + tmp &= addr2[start / BITS_PER_LONG]; + tmp ^= invert; + + /* Handle 1st word. */ + tmp &= BITMAP_FIRST_WORD_MASK(start); + start = round_down(start, BITS_PER_LONG); + + while (!tmp) { + start += BITS_PER_LONG; + if (start >= nbits) + return nbits; + + tmp = addr1[start / BITS_PER_LONG]; + if (addr2) + tmp &= addr2[start / BITS_PER_LONG]; + tmp ^= invert; + } + + return min(start + __ffs(tmp), nbits); } /* * Find the next set bit in a memory region. */ -static inline unsigned long -find_next_bit(const unsigned long *addr, unsigned long size, - unsigned long offset) +static inline unsigned long find_next_bit(const unsigned long *addr, + unsigned long size, + unsigned long offset) { - const unsigned long *p = addr + BITOP_WORD(offset); - unsigned long result = offset & ~(BITS_PER_LONG-1); - unsigned long tmp; - - if (offset >= size) - return size; - size -= result; - offset %= BITS_PER_LONG; - if (offset) { - tmp = *(p++); - tmp &= (~0UL << offset); - if (size < BITS_PER_LONG) - goto found_first; - if (tmp) - goto found_middle; - size -= BITS_PER_LONG; - result += BITS_PER_LONG; - } - while (size & ~(BITS_PER_LONG-1)) { - if ((tmp = *(p++))) - goto found_middle; - result += BITS_PER_LONG; - size -= BITS_PER_LONG; - } - if (!size) - return result; - tmp = *p; - -found_first: - tmp &= (~0UL >> (BITS_PER_LONG - size)); - if (tmp == 0UL) /* Are any bits set? */ - return result + size; /* Nope. */ -found_middle: - return result + __ffs(tmp); + return _find_next_bit(addr, NULL, size, offset, 0UL); } -/* - * This implementation of find_{first,next}_zero_bit was stolen from - * Linus' asm-alpha/bitops.h. - */ -static inline unsigned long -find_next_zero_bit(const unsigned long *addr, unsigned long size, - unsigned long offset) +static inline unsigned long find_next_zero_bit(const unsigned long *addr, + unsigned long size, + unsigned long offset) { - const unsigned long *p = addr + BITOP_WORD(offset); - unsigned long result = offset & ~(BITS_PER_LONG-1); - unsigned long tmp; - - if (offset >= size) - return size; - size -= result; - offset %= BITS_PER_LONG; - if (offset) { - tmp = *(p++); - tmp |= ~0UL >> (BITS_PER_LONG - offset); - if (size < BITS_PER_LONG) - goto found_first; - if (~tmp) - goto found_middle; - size -= BITS_PER_LONG; - result += BITS_PER_LONG; - } - while (size & ~(BITS_PER_LONG-1)) { - if (~(tmp = *(p++))) - goto found_middle; - result += BITS_PER_LONG; - size -= BITS_PER_LONG; - } - if (!size) - return result; - tmp = *p; - -found_first: - tmp |= ~0UL << size; - if (tmp == ~0UL) /* Are any bits zero? */ - return result + size; /* Nope. */ -found_middle: - return result + ffz(tmp); + return _find_next_bit(addr, NULL, size, offset, ~0UL); } + +#define find_first_bit(addr, size) find_next_bit((addr), (size), 0) + #endif