[linux-block.git] / lib / find_bit.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* bit search implementation
 *
 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * Copyright (C) 2008 IBM Corporation
 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
 * (Inspired by David Howell's find_next_bit implementation)
 *
 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
 * size and improve performance, 2015.
 */

#include <linux/bitops.h>
#include <linux/bitmap.h>
#include <linux/export.h>
#include <linux/math.h>
#include <linux/minmax.h>
#include <linux/swab.h>
#include <linux/random.h>

/*
 * Common helper for find_bit() function family
 * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
 * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
 * @size: The bitmap size in bits
 */
#define FIND_FIRST_BIT(FETCH, MUNGE, size)					\
({										\
	unsigned long idx, val, sz = (size);					\
										\
	for (idx = 0; idx * BITS_PER_LONG < sz; idx++) {			\
		val = (FETCH);							\
		if (val) {							\
			sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(val)), sz);	\
			break;							\
		}								\
	}									\
										\
	sz;									\
})

/*
 * Common helper for find_next_bit() function family
 * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
 * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
 * @size: The bitmap size in bits
 * @start: The bitnumber to start searching at
 */
#define FIND_NEXT_BIT(FETCH, MUNGE, size, start)				\
({										\
	unsigned long mask, idx, tmp, sz = (size), __start = (start);		\
										\
	if (unlikely(__start >= sz))						\
		goto out;							\
										\
	mask = MUNGE(BITMAP_FIRST_WORD_MASK(__start));				\
	idx = __start / BITS_PER_LONG;						\
										\
	for (tmp = (FETCH) & mask; !tmp; tmp = (FETCH)) {			\
		if ((idx + 1) * BITS_PER_LONG >= sz)				\
			goto out;						\
		idx++;								\
	}									\
										\
	sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(tmp)), sz);			\
out:										\
	sz;									\
})

#define FIND_NTH_BIT(FETCH, size, num)						\
({										\
	unsigned long sz = (size), nr = (num), idx, w, tmp;			\
										\
	for (idx = 0; (idx + 1) * BITS_PER_LONG <= sz; idx++) {			\
		if (idx * BITS_PER_LONG + nr >= sz)				\
			goto out;						\
										\
		tmp = (FETCH);							\
		w = hweight_long(tmp);						\
		if (w > nr)							\
			goto found;						\
										\
		nr -= w;							\
	}									\
										\
	if (sz % BITS_PER_LONG)							\
		tmp = (FETCH) & BITMAP_LAST_WORD_MASK(sz);			\
found:										\
	sz = idx * BITS_PER_LONG + fns(tmp, nr);				\
out:										\
	sz;									\
})

#ifndef find_first_bit
/*
 * Find the first set bit in a memory region.
 */
unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
{
	return FIND_FIRST_BIT(addr[idx], /* nop */, size);
}
EXPORT_SYMBOL(_find_first_bit);
#endif

#ifndef find_first_and_bit
/*
 * Find the first set bit in two memory regions.
 */
unsigned long _find_first_and_bit(const unsigned long *addr1,
				  const unsigned long *addr2,
				  unsigned long size)
{
	return FIND_FIRST_BIT(addr1[idx] & addr2[idx], /* nop */, size);
}
EXPORT_SYMBOL(_find_first_and_bit);
#endif

/*
 * Find the first bit set in 1st memory region and unset in 2nd.
 */
unsigned long _find_first_andnot_bit(const unsigned long *addr1,
				  const unsigned long *addr2,
				  unsigned long size)
{
	return FIND_FIRST_BIT(addr1[idx] & ~addr2[idx], /* nop */, size);
}
EXPORT_SYMBOL(_find_first_andnot_bit);

/*
 * Find the first set bit in three memory regions.
 */
unsigned long _find_first_and_and_bit(const unsigned long *addr1,
				      const unsigned long *addr2,
				      const unsigned long *addr3,
				      unsigned long size)
{
	return FIND_FIRST_BIT(addr1[idx] & addr2[idx] & addr3[idx], /* nop */, size);
}
EXPORT_SYMBOL(_find_first_and_and_bit);

#ifndef find_first_zero_bit
/*
 * Find the first cleared bit in a memory region.
 */
unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
{
	return FIND_FIRST_BIT(~addr[idx], /* nop */, size);
}
EXPORT_SYMBOL(_find_first_zero_bit);
#endif

#ifndef find_next_bit
unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start)
{
	return FIND_NEXT_BIT(addr[idx], /* nop */, nbits, start);
}
EXPORT_SYMBOL(_find_next_bit);
#endif

unsigned long __find_nth_bit(const unsigned long *addr, unsigned long size, unsigned long n)
{
	return FIND_NTH_BIT(addr[idx], size, n);
}
EXPORT_SYMBOL(__find_nth_bit);

unsigned long __find_nth_and_bit(const unsigned long *addr1, const unsigned long *addr2,
				 unsigned long size, unsigned long n)
{
	return FIND_NTH_BIT(addr1[idx] & addr2[idx], size, n);
}
EXPORT_SYMBOL(__find_nth_and_bit);

unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
				 unsigned long size, unsigned long n)
{
	return FIND_NTH_BIT(addr1[idx] & ~addr2[idx], size, n);
}
EXPORT_SYMBOL(__find_nth_andnot_bit);

unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1,
					const unsigned long *addr2,
					const unsigned long *addr3,
					unsigned long size, unsigned long n)
{
	return FIND_NTH_BIT(addr1[idx] & addr2[idx] & ~addr3[idx], size, n);
}
EXPORT_SYMBOL(__find_nth_and_andnot_bit);

#ifndef find_next_and_bit
unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2,
					unsigned long nbits, unsigned long start)
{
	return FIND_NEXT_BIT(addr1[idx] & addr2[idx], /* nop */, nbits, start);
}
EXPORT_SYMBOL(_find_next_and_bit);
#endif

#ifndef find_next_andnot_bit
unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
					unsigned long nbits, unsigned long start)
{
	return FIND_NEXT_BIT(addr1[idx] & ~addr2[idx], /* nop */, nbits, start);
}
EXPORT_SYMBOL(_find_next_andnot_bit);
#endif

#ifndef find_next_or_bit
unsigned long _find_next_or_bit(const unsigned long *addr1, const unsigned long *addr2,
					unsigned long nbits, unsigned long start)
{
	return FIND_NEXT_BIT(addr1[idx] | addr2[idx], /* nop */, nbits, start);
}
EXPORT_SYMBOL(_find_next_or_bit);
#endif

#ifndef find_next_zero_bit
unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
					 unsigned long start)
{
	return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start);
}
EXPORT_SYMBOL(_find_next_zero_bit);
#endif

#ifndef find_last_bit
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;

		do {
			val &= addr[idx];
			if (val)
				return idx * BITS_PER_LONG + __fls(val);

			val = ~0ul;
		} while (idx--);
	}
	return size;
}
EXPORT_SYMBOL(_find_last_bit);
#endif

unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
			       unsigned long size, unsigned long offset)
{
	offset = find_next_bit(addr, size, offset);
	if (offset == size)
		return size;

	offset = round_down(offset, 8);
	*clump = bitmap_get_value8(addr, offset);

	return offset;
}
EXPORT_SYMBOL(find_next_clump8);

#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[idx], swab, size);
}
EXPORT_SYMBOL(_find_first_zero_bit_le);

#endif

#ifndef find_next_zero_bit_le
unsigned long _find_next_zero_bit_le(const unsigned long *addr,
					unsigned long size, unsigned long offset)
{
	return FIND_NEXT_BIT(~addr[idx], swab, size, offset);
}
EXPORT_SYMBOL(_find_next_zero_bit_le);
#endif

#ifndef find_next_bit_le
unsigned long _find_next_bit_le(const unsigned long *addr,
				unsigned long size, unsigned long offset)
{
	return FIND_NEXT_BIT(addr[idx], swab, size, offset);
}
EXPORT_SYMBOL(_find_next_bit_le);

#endif

#endif /* __BIG_ENDIAN */

/**
 * find_random_bit - find a set bit at random position
 * @addr: The address to base the search on
 * @size: The bitmap size in bits
 *
 * Returns: a position of a random set bit; >= @size otherwise
 */
unsigned long find_random_bit(const unsigned long *addr, unsigned long size)
{
	int w = bitmap_weight(addr, size);

	switch (w) {
	case 0:
		return size;
	case 1:
		/* Performance trick for single-bit bitmaps */
		return find_first_bit(addr, size);
	default:
		return find_nth_bit(addr, size, get_random_u32_below(w));
	}
}
EXPORT_SYMBOL(find_random_bit);
Commit	Line	Data
	1	// SPDX-License-Identifier: GPL-2.0-or-later
	2	/* bit search implementation
	3	*
	4	* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
	5	* Written by David Howells (dhowells@redhat.com)
	6	*
	7	* Copyright (C) 2008 IBM Corporation
	8	* 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
	9	* (Inspired by David Howell's find_next_bit implementation)
	10	*
	11	* Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
	12	* size and improve performance, 2015.
	13	*/
	14
	15	#include <linux/bitops.h>
	16	#include <linux/bitmap.h>
	17	#include <linux/export.h>
	18	#include <linux/math.h>
	19	#include <linux/minmax.h>
	20	#include <linux/swab.h>
	21	#include <linux/random.h>
	22
	23	/*
	24	* Common helper for find_bit() function family
	25	* @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
	26	* @MUNGE: The expression that post-processes a word containing found bit (may be empty)
	27	* @size: The bitmap size in bits
	28	*/
	29	#define FIND_FIRST_BIT(FETCH, MUNGE, size) \
	30	({ \
	31	unsigned long idx, val, sz = (size); \
	32	\
	33	for (idx = 0; idx * BITS_PER_LONG < sz; idx++) { \
	34	val = (FETCH); \
	35	if (val) { \
	36	sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(val)), sz); \
	37	break; \
	38	} \
	39	} \
	40	\
	41	sz; \
	42	})
	43
	44	/*
	45	* Common helper for find_next_bit() function family
	46	* @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
	47	* @MUNGE: The expression that post-processes a word containing found bit (may be empty)
	48	* @size: The bitmap size in bits
	49	* @start: The bitnumber to start searching at
	50	*/
	51	#define FIND_NEXT_BIT(FETCH, MUNGE, size, start) \
	52	({ \
	53	unsigned long mask, idx, tmp, sz = (size), __start = (start); \
	54	\
	55	if (unlikely(__start >= sz)) \
	56	goto out; \
	57	\
	58	mask = MUNGE(BITMAP_FIRST_WORD_MASK(__start)); \
	59	idx = __start / BITS_PER_LONG; \
	60	\
	61	for (tmp = (FETCH) & mask; !tmp; tmp = (FETCH)) { \
	62	if ((idx + 1) * BITS_PER_LONG >= sz) \
	63	goto out; \
	64	idx++; \
	65	} \
	66	\
	67	sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(tmp)), sz); \
	68	out: \
	69	sz; \
	70	})
	71
	72	#define FIND_NTH_BIT(FETCH, size, num) \
	73	({ \
	74	unsigned long sz = (size), nr = (num), idx, w, tmp; \
	75	\
	76	for (idx = 0; (idx + 1) * BITS_PER_LONG <= sz; idx++) { \
	77	if (idx * BITS_PER_LONG + nr >= sz) \
	78	goto out; \
	79	\
	80	tmp = (FETCH); \
	81	w = hweight_long(tmp); \
	82	if (w > nr) \
	83	goto found; \
	84	\
	85	nr -= w; \
	86	} \
	87	\
	88	if (sz % BITS_PER_LONG) \
	89	tmp = (FETCH) & BITMAP_LAST_WORD_MASK(sz); \
	90	found: \
	91	sz = idx * BITS_PER_LONG + fns(tmp, nr); \
	92	out: \
	93	sz; \
	94	})
	95
	96	#ifndef find_first_bit
	97	/*
	98	* Find the first set bit in a memory region.
	99	*/
	100	unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
	101	{
	102	return FIND_FIRST_BIT(addr[idx], /* nop */, size);
	103	}
	104	EXPORT_SYMBOL(_find_first_bit);
	105	#endif
	106
	107	#ifndef find_first_and_bit
	108	/*
	109	* Find the first set bit in two memory regions.
	110	*/
	111	unsigned long _find_first_and_bit(const unsigned long *addr1,
	112	const unsigned long *addr2,
	113	unsigned long size)
	114	{
	115	return FIND_FIRST_BIT(addr1[idx] & addr2[idx], /* nop */, size);
	116	}
	117	EXPORT_SYMBOL(_find_first_and_bit);
	118	#endif
	119
	120	/*
	121	* Find the first bit set in 1st memory region and unset in 2nd.
	122	*/
	123	unsigned long _find_first_andnot_bit(const unsigned long *addr1,
	124	const unsigned long *addr2,
	125	unsigned long size)
	126	{
	127	return FIND_FIRST_BIT(addr1[idx] & ~addr2[idx], /* nop */, size);
	128	}
	129	EXPORT_SYMBOL(_find_first_andnot_bit);
	130
	131	/*
	132	* Find the first set bit in three memory regions.
	133	*/
	134	unsigned long _find_first_and_and_bit(const unsigned long *addr1,
	135	const unsigned long *addr2,
	136	const unsigned long *addr3,
	137	unsigned long size)
	138	{
	139	return FIND_FIRST_BIT(addr1[idx] & addr2[idx] & addr3[idx], /* nop */, size);
	140	}
	141	EXPORT_SYMBOL(_find_first_and_and_bit);
	142
	143	#ifndef find_first_zero_bit
	144	/*
	145	* Find the first cleared bit in a memory region.
	146	*/
	147	unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
	148	{
	149	return FIND_FIRST_BIT(~addr[idx], /* nop */, size);
	150	}
	151	EXPORT_SYMBOL(_find_first_zero_bit);
	152	#endif
	153
	154	#ifndef find_next_bit
	155	unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start)
	156	{
	157	return FIND_NEXT_BIT(addr[idx], /* nop */, nbits, start);
	158	}
	159	EXPORT_SYMBOL(_find_next_bit);
	160	#endif
	161
	162	unsigned long __find_nth_bit(const unsigned long *addr, unsigned long size, unsigned long n)
	163	{
	164	return FIND_NTH_BIT(addr[idx], size, n);
	165	}
	166	EXPORT_SYMBOL(__find_nth_bit);
	167
	168	unsigned long __find_nth_and_bit(const unsigned long addr1, const unsigned long addr2,
	169	unsigned long size, unsigned long n)
	170	{
	171	return FIND_NTH_BIT(addr1[idx] & addr2[idx], size, n);
	172	}
	173	EXPORT_SYMBOL(__find_nth_and_bit);
	174
	175	unsigned long __find_nth_andnot_bit(const unsigned long addr1, const unsigned long addr2,
	176	unsigned long size, unsigned long n)
	177	{
	178	return FIND_NTH_BIT(addr1[idx] & ~addr2[idx], size, n);
	179	}
	180	EXPORT_SYMBOL(__find_nth_andnot_bit);
	181
	182	unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1,
	183	const unsigned long *addr2,
	184	const unsigned long *addr3,
	185	unsigned long size, unsigned long n)
	186	{
	187	return FIND_NTH_BIT(addr1[idx] & addr2[idx] & ~addr3[idx], size, n);
	188	}
	189	EXPORT_SYMBOL(__find_nth_and_andnot_bit);
	190
	191	#ifndef find_next_and_bit
	192	unsigned long _find_next_and_bit(const unsigned long addr1, const unsigned long addr2,
	193	unsigned long nbits, unsigned long start)
	194	{
	195	return FIND_NEXT_BIT(addr1[idx] & addr2[idx], /* nop */, nbits, start);
	196	}
	197	EXPORT_SYMBOL(_find_next_and_bit);
	198	#endif
	199
	200	#ifndef find_next_andnot_bit
	201	unsigned long _find_next_andnot_bit(const unsigned long addr1, const unsigned long addr2,
	202	unsigned long nbits, unsigned long start)
	203	{
	204	return FIND_NEXT_BIT(addr1[idx] & ~addr2[idx], /* nop */, nbits, start);
	205	}
	206	EXPORT_SYMBOL(_find_next_andnot_bit);
	207	#endif
	208
	209	#ifndef find_next_or_bit
	210	unsigned long _find_next_or_bit(const unsigned long addr1, const unsigned long addr2,
	211	unsigned long nbits, unsigned long start)
	212	{
	213	return FIND_NEXT_BIT(addr1[idx] \| addr2[idx], /* nop */, nbits, start);
	214	}
	215	EXPORT_SYMBOL(_find_next_or_bit);
	216	#endif
	217
	218	#ifndef find_next_zero_bit
	219	unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
	220	unsigned long start)
	221	{
	222	return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start);
	223	}
	224	EXPORT_SYMBOL(_find_next_zero_bit);
	225	#endif
	226
	227	#ifndef find_last_bit
	228	unsigned long _find_last_bit(const unsigned long *addr, unsigned long size)
	229	{
	230	if (size) {
	231	unsigned long val = BITMAP_LAST_WORD_MASK(size);
	232	unsigned long idx = (size-1) / BITS_PER_LONG;
	233
	234	do {
	235	val &= addr[idx];
	236	if (val)
	237	return idx * BITS_PER_LONG + __fls(val);
	238
	239	val = ~0ul;
	240	} while (idx--);
	241	}
	242	return size;
	243	}
	244	EXPORT_SYMBOL(_find_last_bit);
	245	#endif
	246
	247	unsigned long find_next_clump8(unsigned long clump, const unsigned long addr,
	248	unsigned long size, unsigned long offset)
	249	{
	250	offset = find_next_bit(addr, size, offset);
	251	if (offset == size)
	252	return size;
	253
	254	offset = round_down(offset, 8);
	255	*clump = bitmap_get_value8(addr, offset);
	256
	257	return offset;
	258	}
	259	EXPORT_SYMBOL(find_next_clump8);
	260
	261	#ifdef __BIG_ENDIAN
	262
	263	#ifndef find_first_zero_bit_le
	264	/*
	265	* Find the first cleared bit in an LE memory region.
	266	*/
	267	unsigned long _find_first_zero_bit_le(const unsigned long *addr, unsigned long size)
	268	{
	269	return FIND_FIRST_BIT(~addr[idx], swab, size);
	270	}
	271	EXPORT_SYMBOL(_find_first_zero_bit_le);
	272
	273	#endif
	274
	275	#ifndef find_next_zero_bit_le
	276	unsigned long _find_next_zero_bit_le(const unsigned long *addr,
	277	unsigned long size, unsigned long offset)
	278	{
	279	return FIND_NEXT_BIT(~addr[idx], swab, size, offset);
	280	}
	281	EXPORT_SYMBOL(_find_next_zero_bit_le);
	282	#endif
	283
	284	#ifndef find_next_bit_le
	285	unsigned long _find_next_bit_le(const unsigned long *addr,
	286	unsigned long size, unsigned long offset)
	287	{
	288	return FIND_NEXT_BIT(addr[idx], swab, size, offset);
	289	}
	290	EXPORT_SYMBOL(_find_next_bit_le);
	291
	292	#endif
	293
	294	#endif /* __BIG_ENDIAN */
	295
	296	/**
	297	* find_random_bit - find a set bit at random position
	298	* @addr: The address to base the search on
	299	* @size: The bitmap size in bits
	300	*
	301	* Returns: a position of a random set bit; >= @size otherwise
	302	*/
	303	unsigned long find_random_bit(const unsigned long *addr, unsigned long size)
	304	{
	305	int w = bitmap_weight(addr, size);
	306
	307	switch (w) {
	308	case 0:
	309	return size;
	310	case 1:
	311	/* Performance trick for single-bit bitmaps */
	312	return find_first_bit(addr, size);
	313	default:
	314	return find_nth_bit(addr, size, get_random_u32_below(w));
	315	}
	316	}
	317	EXPORT_SYMBOL(find_random_bit);