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-rw-r--r--lib/sbitmap.c532
1 files changed, 532 insertions, 0 deletions
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
new file mode 100644
index 000000000000..80aa8d5463fa
--- /dev/null
+++ b/lib/sbitmap.c
@@ -0,0 +1,532 @@
+/*
+ * 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/sched.h>
+#include <linux/random.h>
+#include <linux/sbitmap.h>
+#include <linux/seq_file.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;
+}
+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;
+ }
+}
+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(nr, word))
+ break;
+
+ hint = nr + 1;
+ if (hint >= depth - 1)
+ hint = 0;
+ }
+
+ 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);
+
+ for (i = 0; i < sb->map_nr; i++) {
+ nr = __sbitmap_get_word(&sb->map[index].word,
+ sb->map[index].depth,
+ 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;
+}
+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++) {
+ 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;
+ }
+
+ /* 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)
+ return true;
+ }
+ return false;
+}
+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;
+}
+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;
+}
+EXPORT_SYMBOL_GPL(sbitmap_weight);
+
+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));
+ 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 int word_bits = READ_ONCE(sb->map[i].depth);
+
+ 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(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;
+}
+
+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;
+}
+EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
+
+void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
+{
+ unsigned int wake_batch = sbq_calc_wake_batch(depth);
+ int i;
+
+ if (sbq->wake_batch != wake_batch) {
+ WRITE_ONCE(sbq->wake_batch, wake_batch);
+ /*
+ * Pairs with the memory barrier in sbq_wake_up() to ensure that
+ * the batch size is updated before the wait counts.
+ */
+ smp_mb__before_atomic();
+ for (i = 0; i < SBQ_WAIT_QUEUES; i++)
+ atomic_set(&sbq->ws[i].wait_cnt, 1);
+ }
+ 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;
+
+ 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);
+
+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;
+}
+
+static void sbq_wake_up(struct sbitmap_queue *sbq)
+{
+ struct sbq_wait_state *ws;
+ unsigned int wake_batch;
+ int wait_cnt;
+
+ /*
+ * Pairs with the memory barrier in set_current_state() to ensure the
+ * proper ordering of clear_bit()/waitqueue_active() in the waker and
+ * test_and_set_bit()/prepare_to_wait()/finish_wait() in the waiter. See
+ * the comment on waitqueue_active(). This is __after_atomic because we
+ * just did clear_bit() in the caller.
+ */
+ smp_mb__after_atomic();
+
+ ws = sbq_wake_ptr(sbq);
+ if (!ws)
+ return;
+
+ wait_cnt = atomic_dec_return(&ws->wait_cnt);
+ if (wait_cnt <= 0) {
+ 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();
+ /*
+ * If there are concurrent callers to sbq_wake_up(), the last
+ * one to decrement the wait count below zero will bump it back
+ * up. If there is a concurrent resize, the count reset will
+ * either cause the cmpxchg to fail or overwrite after the
+ * cmpxchg.
+ */
+ atomic_cmpxchg(&ws->wait_cnt, wait_cnt, wait_cnt + wake_batch);
+ sbq_index_atomic_inc(&sbq->wake_index);
+ wake_up(&ws->wait);
+ }
+}
+
+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;
+}
+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
+ * sbq_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_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);
+}
+EXPORT_SYMBOL_GPL(sbitmap_queue_show);
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