1 files changed, 692 insertions, 0 deletions

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
new file mode 100644
index 000000000..267aa7709
--- /dev/null
+++ b/lib/sbitmap.c
@@ -0,0 +1,692 @@
+// 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);