cregit-Linux how code gets into the kernel

Release 4.10 lib/sbitmap.c

Directory: lib
/*
 * Copyright (C) 2016 Facebook
 * Copyright (C) 2013-2014 Jens Axboe
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#include <linux/random.h>
#include <linux/sbitmap.h>


int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift, gfp_t flags, int node) { unsigned int bits_per_word; unsigned int i; if (shift < 0) { shift = ilog2(BITS_PER_LONG); /* * If the bitmap is small, shrink the number of bits per word so * we spread over a few cachelines, at least. If less than 4 * bits, just forget about it, it's not going to work optimally * anyway. */ if (depth >= 4) { while ((4U << shift) > depth) shift--; } } bits_per_word = 1U << shift; if (bits_per_word > BITS_PER_LONG) return -EINVAL; sb->shift = shift; sb->depth = depth; sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word); if (depth == 0) { sb->map = NULL; return 0; } sb->map = kzalloc_node(sb->map_nr * sizeof(*sb->map), flags, node); if (!sb->map) return -ENOMEM; for (i = 0; i < sb->map_nr; i++) { sb->map[i].depth = min(depth, bits_per_word); depth -= sb->map[i].depth; } return 0; }

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EXPORT_SYMBOL_GPL(sbitmap_init_node);
void sbitmap_resize(struct sbitmap *sb, unsigned int depth) { unsigned int bits_per_word = 1U << sb->shift; unsigned int i; sb->depth = depth; sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word); for (i = 0; i < sb->map_nr; i++) { sb->map[i].depth = min(depth, bits_per_word); depth -= sb->map[i].depth; } }

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EXPORT_SYMBOL_GPL(sbitmap_resize);
static int __sbitmap_get_word(struct sbitmap_word *word, unsigned int hint, bool wrap) { unsigned int orig_hint = hint; int nr; while (1) { nr = find_next_zero_bit(&word->word, word->depth, hint); if (unlikely(nr >= word->depth)) { /* * We started with an offset, and we didn't reset the * offset to 0 in a failure case, so start from 0 to * exhaust the map. */ if (orig_hint && hint && wrap) { hint = orig_hint = 0; continue; } return -1; } if (!test_and_set_bit(nr, &word->word)) break; hint = nr + 1; if (hint >= word->depth - 1) hint = 0; } return nr; }

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int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin) { unsigned int i, index; int nr = -1; index = SB_NR_TO_INDEX(sb, alloc_hint); for (i = 0; i < sb->map_nr; i++) { nr = __sbitmap_get_word(&sb->map[index], SB_NR_TO_BIT(sb, alloc_hint), !round_robin); if (nr != -1) { nr += index << sb->shift; break; } /* Jump to next index. */ index++; alloc_hint = index << sb->shift; if (index >= sb->map_nr) { index = 0; alloc_hint = 0; } } return nr; }

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EXPORT_SYMBOL_GPL(sbitmap_get);
bool sbitmap_any_bit_set(const struct sbitmap *sb) { unsigned int i; for (i = 0; i < sb->map_nr; i++) { if (sb->map[i].word) return true; } return false; }

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EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);
bool sbitmap_any_bit_clear(const struct sbitmap *sb) { unsigned int i; for (i = 0; i < sb->map_nr; i++) { const struct sbitmap_word *word = &sb->map[i]; unsigned long ret; ret = find_first_zero_bit(&word->word, word->depth); if (ret < word->depth) return true; } return false; }

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EXPORT_SYMBOL_GPL(sbitmap_any_bit_clear);
unsigned int sbitmap_weight(const struct sbitmap *sb) { unsigned int i, weight = 0; for (i = 0; i < sb->map_nr; i++) { const struct sbitmap_word *word = &sb->map[i]; weight += bitmap_weight(&word->word, word->depth); } return weight; }

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EXPORT_SYMBOL_GPL(sbitmap_weight);
static unsigned int sbq_calc_wake_batch(unsigned int depth) { unsigned int wake_batch; /* * For each batch, we wake up one queue. We need to make sure that our * batch size is small enough that the full depth of the bitmap is * enough to wake up all of the queues. */ wake_batch = SBQ_WAKE_BATCH; if (wake_batch > depth / SBQ_WAIT_QUEUES) wake_batch = max(1U, depth / SBQ_WAIT_QUEUES); return wake_batch; }

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int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, int shift, bool round_robin, gfp_t flags, int node) { int ret; int i; ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node); if (ret) return ret; sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags); if (!sbq->alloc_hint) { sbitmap_free(&sbq->sb); return -ENOMEM; } if (depth && !round_robin) { for_each_possible_cpu(i) *per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth; } sbq->wake_batch = sbq_calc_wake_batch(depth); atomic_set(&sbq->wake_index, 0); sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node); if (!sbq->ws) { free_percpu(sbq->alloc_hint); sbitmap_free(&sbq->sb); return -ENOMEM; } for (i = 0; i < SBQ_WAIT_QUEUES; i++) { init_waitqueue_head(&sbq->ws[i].wait); atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch); } sbq->round_robin = round_robin; return 0; }

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EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth) { sbq->wake_batch = sbq_calc_wake_batch(depth); sbitmap_resize(&sbq->sb, depth); }

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EXPORT_SYMBOL_GPL(sbitmap_queue_resize);
int __sbitmap_queue_get(struct sbitmap_queue *sbq) { unsigned int hint, depth; int nr; hint = this_cpu_read(*sbq->alloc_hint); depth = READ_ONCE(sbq->sb.depth); if (unlikely(hint >= depth)) { hint = depth ? prandom_u32() % depth : 0; this_cpu_write(*sbq->alloc_hint, hint); } nr = sbitmap_get(&sbq->sb, hint, sbq->round_robin); if (nr == -1) { /* If the map is full, a hint won't do us much good. */ this_cpu_write(*sbq->alloc_hint, 0); } else if (nr == hint || unlikely(sbq->round_robin)) { /* Only update the hint if we used it. */ hint = nr + 1; if (hint >= depth - 1) hint = 0; this_cpu_write(*sbq->alloc_hint, hint); } return nr; }

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EXPORT_SYMBOL_GPL(__sbitmap_queue_get);
static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq) { int i, wake_index; wake_index = atomic_read(&sbq->wake_index); for (i = 0; i < SBQ_WAIT_QUEUES; i++) { struct sbq_wait_state *ws = &sbq->ws[wake_index]; if (waitqueue_active(&ws->wait)) { int o = atomic_read(&sbq->wake_index); if (wake_index != o) atomic_cmpxchg(&sbq->wake_index, o, wake_index); return ws; } wake_index = sbq_index_inc(wake_index); } return NULL; }

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static void sbq_wake_up(struct sbitmap_queue *sbq) { struct sbq_wait_state *ws; int wait_cnt; /* Ensure that the wait list checks occur after clear_bit(). */ smp_mb(); ws = sbq_wake_ptr(sbq); if (!ws) return; wait_cnt = atomic_dec_return(&ws->wait_cnt); if (unlikely(wait_cnt < 0)) wait_cnt = atomic_inc_return(&ws->wait_cnt); if (wait_cnt == 0) { atomic_add(sbq->wake_batch, &ws->wait_cnt); sbq_index_atomic_inc(&sbq->wake_index); wake_up(&ws->wait); } }

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void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, unsigned int cpu) { sbitmap_clear_bit(&sbq->sb, nr); sbq_wake_up(sbq); if (likely(!sbq->round_robin && nr < sbq->sb.depth)) *per_cpu_ptr(sbq->alloc_hint, cpu) = nr; }

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EXPORT_SYMBOL_GPL(sbitmap_queue_clear);
void sbitmap_queue_wake_all(struct sbitmap_queue *sbq) { int i, wake_index; /* * Make sure all changes prior to this are visible from other CPUs. */ smp_mb(); wake_index = atomic_read(&sbq->wake_index); for (i = 0; i < SBQ_WAIT_QUEUES; i++) { struct sbq_wait_state *ws = &sbq->ws[wake_index]; if (waitqueue_active(&ws->wait)) wake_up(&ws->wait); wake_index = sbq_index_inc(wake_index); } }

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EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);

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Directory: lib
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