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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * Copyright (C) 2016 Facebook
- * Copyright (C) 2013-2014 Jens Axboe
- */
- #include <linux/sched.h>
- #include <linux/random.h>
- #include <linux/sbitmap.h>
- #include <linux/seq_file.h>
- /*
- * See if we have deferred clears that we can batch move
- */
- static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
- {
- unsigned long mask, val;
- bool ret = false;
- unsigned long flags;
- spin_lock_irqsave(&sb->map[index].swap_lock, flags);
- if (!sb->map[index].cleared)
- goto out_unlock;
- /*
- * First get a stable cleared mask, setting the old mask to 0.
- */
- mask = xchg(&sb->map[index].cleared, 0);
- /*
- * Now clear the masked bits in our free word
- */
- do {
- val = sb->map[index].word;
- } while (cmpxchg(&sb->map[index].word, val, val & ~mask) != val);
- ret = true;
- out_unlock:
- spin_unlock_irqrestore(&sb->map[index].swap_lock, flags);
- return ret;
- }
- 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 = kcalloc_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;
- spin_lock_init(&sb->map[i].swap_lock);
- }
- return 0;
- }
- 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;
- for (i = 0; i < sb->map_nr; i++)
- sbitmap_deferred_clear(sb, 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;
- }
- }
- EXPORT_SYMBOL_GPL(sbitmap_resize);
- static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
- unsigned int hint, bool wrap)
- {
- unsigned int orig_hint = hint;
- int nr;
- while (1) {
- nr = find_next_zero_bit(word, depth, hint);
- if (unlikely(nr >= 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_lock(nr, word))
- break;
- hint = nr + 1;
- if (hint >= depth - 1)
- hint = 0;
- }
- return nr;
- }
- static int sbitmap_find_bit_in_index(struct sbitmap *sb, int index,
- unsigned int alloc_hint, bool round_robin)
- {
- int nr;
- do {
- nr = __sbitmap_get_word(&sb->map[index].word,
- sb->map[index].depth, alloc_hint,
- !round_robin);
- if (nr != -1)
- break;
- if (!sbitmap_deferred_clear(sb, index))
- break;
- } while (1);
- return nr;
- }
- 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);
- /*
- * Unless we're doing round robin tag allocation, just use the
- * alloc_hint to find the right word index. No point in looping
- * twice in find_next_zero_bit() for that case.
- */
- if (round_robin)
- alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
- else
- alloc_hint = 0;
- for (i = 0; i < sb->map_nr; i++) {
- nr = sbitmap_find_bit_in_index(sb, index, alloc_hint,
- round_robin);
- if (nr != -1) {
- nr += index << sb->shift;
- break;
- }
- /* Jump to next index. */
- alloc_hint = 0;
- if (++index >= sb->map_nr)
- index = 0;
- }
- return nr;
- }
- EXPORT_SYMBOL_GPL(sbitmap_get);
- int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
- unsigned long shallow_depth)
- {
- unsigned int i, index;
- int nr = -1;
- index = SB_NR_TO_INDEX(sb, alloc_hint);
- for (i = 0; i < sb->map_nr; i++) {
- again:
- nr = __sbitmap_get_word(&sb->map[index].word,
- min(sb->map[index].depth, shallow_depth),
- SB_NR_TO_BIT(sb, alloc_hint), true);
- if (nr != -1) {
- nr += index << sb->shift;
- break;
- }
- if (sbitmap_deferred_clear(sb, index))
- goto again;
- /* Jump to next index. */
- index++;
- alloc_hint = index << sb->shift;
- if (index >= sb->map_nr) {
- index = 0;
- alloc_hint = 0;
- }
- }
- return nr;
- }
- EXPORT_SYMBOL_GPL(sbitmap_get_shallow);
- 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 & ~sb->map[i].cleared)
- return true;
- }
- return false;
- }
- EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);
- static unsigned int __sbitmap_weight(const struct sbitmap *sb, bool set)
- {
- unsigned int i, weight = 0;
- for (i = 0; i < sb->map_nr; i++) {
- const struct sbitmap_word *word = &sb->map[i];
- if (set)
- weight += bitmap_weight(&word->word, word->depth);
- else
- weight += bitmap_weight(&word->cleared, word->depth);
- }
- return weight;
- }
- static unsigned int sbitmap_weight(const struct sbitmap *sb)
- {
- return __sbitmap_weight(sb, true);
- }
- static unsigned int sbitmap_cleared(const struct sbitmap *sb)
- {
- return __sbitmap_weight(sb, false);
- }
- void sbitmap_show(struct sbitmap *sb, struct seq_file *m)
- {
- seq_printf(m, "depth=%u\n", sb->depth);
- seq_printf(m, "busy=%u\n", sbitmap_weight(sb) - sbitmap_cleared(sb));
- seq_printf(m, "cleared=%u\n", sbitmap_cleared(sb));
- seq_printf(m, "bits_per_word=%u\n", 1U << sb->shift);
- seq_printf(m, "map_nr=%u\n", sb->map_nr);
- }
- EXPORT_SYMBOL_GPL(sbitmap_show);
- static inline void emit_byte(struct seq_file *m, unsigned int offset, u8 byte)
- {
- if ((offset & 0xf) == 0) {
- if (offset != 0)
- seq_putc(m, '\n');
- seq_printf(m, "%08x:", offset);
- }
- if ((offset & 0x1) == 0)
- seq_putc(m, ' ');
- seq_printf(m, "%02x", byte);
- }
- void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m)
- {
- u8 byte = 0;
- unsigned int byte_bits = 0;
- unsigned int offset = 0;
- int i;
- for (i = 0; i < sb->map_nr; i++) {
- unsigned long word = READ_ONCE(sb->map[i].word);
- unsigned long cleared = READ_ONCE(sb->map[i].cleared);
- unsigned int word_bits = READ_ONCE(sb->map[i].depth);
- word &= ~cleared;
- while (word_bits > 0) {
- unsigned int bits = min(8 - byte_bits, word_bits);
- byte |= (word & (BIT(bits) - 1)) << byte_bits;
- byte_bits += bits;
- if (byte_bits == 8) {
- emit_byte(m, offset, byte);
- byte = 0;
- byte_bits = 0;
- offset++;
- }
- word >>= bits;
- word_bits -= bits;
- }
- }
- if (byte_bits) {
- emit_byte(m, offset, byte);
- offset++;
- }
- if (offset)
- seq_putc(m, '\n');
- }
- EXPORT_SYMBOL_GPL(sbitmap_bitmap_show);
- static unsigned int sbq_calc_wake_batch(struct sbitmap_queue *sbq,
- unsigned int depth)
- {
- unsigned int wake_batch;
- unsigned int shallow_depth;
- /*
- * 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,
- * potentially limited by a shallow depth, is enough to wake up all of
- * the queues.
- *
- * Each full word of the bitmap has bits_per_word bits, and there might
- * be a partial word. There are depth / bits_per_word full words and
- * depth % bits_per_word bits left over. In bitwise arithmetic:
- *
- * bits_per_word = 1 << shift
- * depth / bits_per_word = depth >> shift
- * depth % bits_per_word = depth & ((1 << shift) - 1)
- *
- * Each word can be limited to sbq->min_shallow_depth bits.
- */
- shallow_depth = min(1U << sbq->sb.shift, sbq->min_shallow_depth);
- depth = ((depth >> sbq->sb.shift) * shallow_depth +
- min(depth & ((1U << sbq->sb.shift) - 1), shallow_depth));
- wake_batch = clamp_t(unsigned int, depth / SBQ_WAIT_QUEUES, 1,
- SBQ_WAKE_BATCH);
- return wake_batch;
- }
- 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->min_shallow_depth = UINT_MAX;
- sbq->wake_batch = sbq_calc_wake_batch(sbq, depth);
- atomic_set(&sbq->wake_index, 0);
- atomic_set(&sbq->ws_active, 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;
- }
- EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
- static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
- unsigned int depth)
- {
- unsigned int wake_batch = sbq_calc_wake_batch(sbq, depth);
- int i;
- if (sbq->wake_batch != wake_batch) {
- WRITE_ONCE(sbq->wake_batch, wake_batch);
- /*
- * Pairs with the memory barrier in sbitmap_queue_wake_up()
- * to ensure that the batch size is updated before the wait
- * counts.
- */
- smp_mb();
- for (i = 0; i < SBQ_WAIT_QUEUES; i++)
- atomic_set(&sbq->ws[i].wait_cnt, 1);
- }
- }
- void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
- {
- sbitmap_queue_update_wake_batch(sbq, depth);
- sbitmap_resize(&sbq->sb, depth);
- }
- 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;
- }
- EXPORT_SYMBOL_GPL(__sbitmap_queue_get);
- int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
- unsigned int shallow_depth)
- {
- unsigned int hint, depth;
- int nr;
- WARN_ON_ONCE(shallow_depth < sbq->min_shallow_depth);
- 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_shallow(&sbq->sb, hint, shallow_depth);
- 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;
- }
- EXPORT_SYMBOL_GPL(__sbitmap_queue_get_shallow);
- void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
- unsigned int min_shallow_depth)
- {
- sbq->min_shallow_depth = min_shallow_depth;
- sbitmap_queue_update_wake_batch(sbq, sbq->sb.depth);
- }
- EXPORT_SYMBOL_GPL(sbitmap_queue_min_shallow_depth);
- static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
- {
- int i, wake_index;
- if (!atomic_read(&sbq->ws_active))
- return NULL;
- 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)) {
- if (wake_index != atomic_read(&sbq->wake_index))
- atomic_set(&sbq->wake_index, wake_index);
- return ws;
- }
- wake_index = sbq_index_inc(wake_index);
- }
- return NULL;
- }
- static bool __sbq_wake_up(struct sbitmap_queue *sbq)
- {
- struct sbq_wait_state *ws;
- unsigned int wake_batch;
- int wait_cnt;
- ws = sbq_wake_ptr(sbq);
- if (!ws)
- return false;
- wait_cnt = atomic_dec_return(&ws->wait_cnt);
- if (wait_cnt <= 0) {
- int ret;
- wake_batch = READ_ONCE(sbq->wake_batch);
- /*
- * Pairs with the memory barrier in sbitmap_queue_resize() to
- * ensure that we see the batch size update before the wait
- * count is reset.
- */
- smp_mb__before_atomic();
- /*
- * For concurrent callers of this, the one that failed the
- * atomic_cmpxhcg() race should call this function again
- * to wakeup a new batch on a different 'ws'.
- */
- ret = atomic_cmpxchg(&ws->wait_cnt, wait_cnt, wake_batch);
- if (ret == wait_cnt) {
- sbq_index_atomic_inc(&sbq->wake_index);
- wake_up_nr(&ws->wait, wake_batch);
- return false;
- }
- return true;
- }
- return false;
- }
- void sbitmap_queue_wake_up(struct sbitmap_queue *sbq)
- {
- while (__sbq_wake_up(sbq))
- ;
- }
- EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up);
- void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
- unsigned int cpu)
- {
- /*
- * Once the clear bit is set, the bit may be allocated out.
- *
- * Orders READ/WRITE on the asssociated instance(such as request
- * of blk_mq) by this bit for avoiding race with re-allocation,
- * and its pair is the memory barrier implied in __sbitmap_get_word.
- *
- * One invariant is that the clear bit has to be zero when the bit
- * is in use.
- */
- smp_mb__before_atomic();
- sbitmap_deferred_clear_bit(&sbq->sb, nr);
- /*
- * Pairs with the memory barrier in set_current_state() to ensure the
- * proper ordering of clear_bit_unlock()/waitqueue_active() in the waker
- * and test_and_set_bit_lock()/prepare_to_wait()/finish_wait() in the
- * waiter. See the comment on waitqueue_active().
- */
- smp_mb__after_atomic();
- sbitmap_queue_wake_up(sbq);
- if (likely(!sbq->round_robin && nr < sbq->sb.depth))
- *per_cpu_ptr(sbq->alloc_hint, cpu) = nr;
- }
- EXPORT_SYMBOL_GPL(sbitmap_queue_clear);
- void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
- {
- int i, wake_index;
- /*
- * Pairs with the memory barrier in set_current_state() like in
- * sbitmap_queue_wake_up().
- */
- 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);
- }
- }
- EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);
- void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m)
- {
- bool first;
- int i;
- sbitmap_show(&sbq->sb, m);
- seq_puts(m, "alloc_hint={");
- first = true;
- for_each_possible_cpu(i) {
- if (!first)
- seq_puts(m, ", ");
- first = false;
- seq_printf(m, "%u", *per_cpu_ptr(sbq->alloc_hint, i));
- }
- seq_puts(m, "}\n");
- seq_printf(m, "wake_batch=%u\n", sbq->wake_batch);
- seq_printf(m, "wake_index=%d\n", atomic_read(&sbq->wake_index));
- seq_printf(m, "ws_active=%d\n", atomic_read(&sbq->ws_active));
- seq_puts(m, "ws={\n");
- for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
- struct sbq_wait_state *ws = &sbq->ws[i];
- seq_printf(m, "\t{.wait_cnt=%d, .wait=%s},\n",
- atomic_read(&ws->wait_cnt),
- waitqueue_active(&ws->wait) ? "active" : "inactive");
- }
- seq_puts(m, "}\n");
- seq_printf(m, "round_robin=%d\n", sbq->round_robin);
- seq_printf(m, "min_shallow_depth=%u\n", sbq->min_shallow_depth);
- }
- EXPORT_SYMBOL_GPL(sbitmap_queue_show);
- void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
- struct sbq_wait_state *ws,
- struct sbq_wait *sbq_wait)
- {
- if (!sbq_wait->sbq) {
- sbq_wait->sbq = sbq;
- atomic_inc(&sbq->ws_active);
- add_wait_queue(&ws->wait, &sbq_wait->wait);
- }
- }
- EXPORT_SYMBOL_GPL(sbitmap_add_wait_queue);
- void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait)
- {
- list_del_init(&sbq_wait->wait.entry);
- if (sbq_wait->sbq) {
- atomic_dec(&sbq_wait->sbq->ws_active);
- sbq_wait->sbq = NULL;
- }
- }
- EXPORT_SYMBOL_GPL(sbitmap_del_wait_queue);
- void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
- struct sbq_wait_state *ws,
- struct sbq_wait *sbq_wait, int state)
- {
- if (!sbq_wait->sbq) {
- atomic_inc(&sbq->ws_active);
- sbq_wait->sbq = sbq;
- }
- prepare_to_wait_exclusive(&ws->wait, &sbq_wait->wait, state);
- }
- EXPORT_SYMBOL_GPL(sbitmap_prepare_to_wait);
- void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
- struct sbq_wait *sbq_wait)
- {
- finish_wait(&ws->wait, &sbq_wait->wait);
- if (sbq_wait->sbq) {
- atomic_dec(&sbq->ws_active);
- sbq_wait->sbq = NULL;
- }
- }
- EXPORT_SYMBOL_GPL(sbitmap_finish_wait);
|