[mirror_ubuntu-artful-kernel.git] / block / blk-mq-tag.c

/*
 * Fast and scalable bitmap tagging variant. Uses sparser bitmaps spread
 * over multiple cachelines to avoid ping-pong between multiple submitters
 * or submitter and completer. Uses rolling wakeups to avoid falling of
 * the scaling cliff when we run out of tags and have to start putting
 * submitters to sleep.
 *
 * Uses active queue tracking to support fairer distribution of tags
 * between multiple submitters when a shared tag map is used.
 *
 * Copyright (C) 2013-2014 Jens Axboe
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/random.h>

#include <linux/blk-mq.h>
#include "blk.h"
#include "blk-mq.h"
#include "blk-mq-tag.h"

static bool bt_has_free_tags(struct blk_mq_bitmap_tags *bt)
{
	int i;

	for (i = 0; i < bt->map_nr; i++) {
		struct blk_align_bitmap *bm = &bt->map[i];
		int ret;

		ret = find_first_zero_bit(&bm->word, bm->depth);
		if (ret < bm->depth)
			return true;
	}

	return false;
}

bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
{
	if (!tags)
		return true;

	return bt_has_free_tags(&tags->bitmap_tags);
}

static inline void bt_index_inc(unsigned int *index)
{
	*index = (*index + 1) & (BT_WAIT_QUEUES - 1);
}

/*
 * If a previously inactive queue goes active, bump the active user count.
 */
bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
{
	if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
	    !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
		atomic_inc(&hctx->tags->active_queues);

	return true;
}

/*
 * Wakeup all potentially sleeping on normal (non-reserved) tags
 */
static void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags)
{
	struct blk_mq_bitmap_tags *bt;
	int i, wake_index;

	bt = &tags->bitmap_tags;
	wake_index = bt->wake_index;
	for (i = 0; i < BT_WAIT_QUEUES; i++) {
		struct bt_wait_state *bs = &bt->bs[wake_index];

		if (waitqueue_active(&bs->wait))
			wake_up(&bs->wait);

		bt_index_inc(&wake_index);
	}
}

/*
 * If a previously busy queue goes inactive, potential waiters could now
 * be allowed to queue. Wake them up and check.
 */
void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
{
	struct blk_mq_tags *tags = hctx->tags;

	if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
		return;

	atomic_dec(&tags->active_queues);

	blk_mq_tag_wakeup_all(tags);
}

/*
 * For shared tag users, we track the number of currently active users
 * and attempt to provide a fair share of the tag depth for each of them.
 */
static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
				  struct blk_mq_bitmap_tags *bt)
{
	unsigned int depth, users;

	if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_SHARED))
		return true;
	if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
		return true;

	/*
	 * Don't try dividing an ant
	 */
	if (bt->depth == 1)
		return true;

	users = atomic_read(&hctx->tags->active_queues);
	if (!users)
		return true;

	/*
	 * Allow at least some tags
	 */
	depth = max((bt->depth + users - 1) / users, 4U);
	return atomic_read(&hctx->nr_active) < depth;
}

static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
{
	int tag, org_last_tag, end;

	org_last_tag = last_tag;
	end = bm->depth;
	do {
restart:
		tag = find_next_zero_bit(&bm->word, end, last_tag);
		if (unlikely(tag >= end)) {
			/*
			 * We started with an offset, start from 0 to
			 * exhaust the map.
			 */
			if (org_last_tag && last_tag) {
				end = last_tag;
				last_tag = 0;
				goto restart;
			}
			return -1;
		}
		last_tag = tag + 1;
	} while (test_and_set_bit_lock(tag, &bm->word));

	return tag;
}

/*
 * Straight forward bitmap tag implementation, where each bit is a tag
 * (cleared == free, and set == busy). The small twist is using per-cpu
 * last_tag caches, which blk-mq stores in the blk_mq_ctx software queue
 * contexts. This enables us to drastically limit the space searched,
 * without dirtying an extra shared cacheline like we would if we stored
 * the cache value inside the shared blk_mq_bitmap_tags structure. On top
 * of that, each word of tags is in a separate cacheline. This means that
 * multiple users will tend to stick to different cachelines, at least
 * until the map is exhausted.
 */
static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt,
		    unsigned int *tag_cache)
{
	unsigned int last_tag, org_last_tag;
	int index, i, tag;

	if (!hctx_may_queue(hctx, bt))
		return -1;

	last_tag = org_last_tag = *tag_cache;
	index = TAG_TO_INDEX(bt, last_tag);

	for (i = 0; i < bt->map_nr; i++) {
		tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag));
		if (tag != -1) {
			tag += (index << bt->bits_per_word);
			goto done;
		}

		last_tag = 0;
		if (++index >= bt->map_nr)
			index = 0;
	}

	*tag_cache = 0;
	return -1;

	/*
	 * Only update the cache from the allocation path, if we ended
	 * up using the specific cached tag.
	 */
done:
	if (tag == org_last_tag) {
		last_tag = tag + 1;
		if (last_tag >= bt->depth - 1)
			last_tag = 0;

		*tag_cache = last_tag;
	}

	return tag;
}

static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt,
					 struct blk_mq_hw_ctx *hctx)
{
	struct bt_wait_state *bs;

	if (!hctx)
		return &bt->bs[0];

	bs = &bt->bs[hctx->wait_index];
	bt_index_inc(&hctx->wait_index);
	return bs;
}

static int bt_get(struct blk_mq_bitmap_tags *bt, struct blk_mq_hw_ctx *hctx,
		  unsigned int *last_tag, gfp_t gfp)
{
	struct bt_wait_state *bs;
	DEFINE_WAIT(wait);
	int tag;

	tag = __bt_get(hctx, bt, last_tag);
	if (tag != -1)
		return tag;

	if (!(gfp & __GFP_WAIT))
		return -1;

	bs = bt_wait_ptr(bt, hctx);
	do {
		bool was_empty;

		was_empty = list_empty(&wait.task_list);
		prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE);

		tag = __bt_get(hctx, bt, last_tag);
		if (tag != -1)
			break;

		if (was_empty)
			atomic_set(&bs->wait_cnt, bt->wake_cnt);

		io_schedule();
	} while (1);

	finish_wait(&bs->wait, &wait);
	return tag;
}

static unsigned int __blk_mq_get_tag(struct blk_mq_tags *tags,
				     struct blk_mq_hw_ctx *hctx,
				     unsigned int *last_tag, gfp_t gfp)
{
	int tag;

	tag = bt_get(&tags->bitmap_tags, hctx, last_tag, gfp);
	if (tag >= 0)
		return tag + tags->nr_reserved_tags;

	return BLK_MQ_TAG_FAIL;
}

static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_tags *tags,
					      gfp_t gfp)
{
	int tag, zero = 0;

	if (unlikely(!tags->nr_reserved_tags)) {
		WARN_ON_ONCE(1);
		return BLK_MQ_TAG_FAIL;
	}

	tag = bt_get(&tags->breserved_tags, NULL, &zero, gfp);
	if (tag < 0)
		return BLK_MQ_TAG_FAIL;

	return tag;
}

unsigned int blk_mq_get_tag(struct blk_mq_hw_ctx *hctx, unsigned int *last_tag,
			    gfp_t gfp, bool reserved)
{
	if (!reserved)
		return __blk_mq_get_tag(hctx->tags, hctx, last_tag, gfp);

	return __blk_mq_get_reserved_tag(hctx->tags, gfp);
}

static struct bt_wait_state *bt_wake_ptr(struct blk_mq_bitmap_tags *bt)
{
	int i, wake_index;

	wake_index = bt->wake_index;
	for (i = 0; i < BT_WAIT_QUEUES; i++) {
		struct bt_wait_state *bs = &bt->bs[wake_index];

		if (waitqueue_active(&bs->wait)) {
			if (wake_index != bt->wake_index)
				bt->wake_index = wake_index;

			return bs;
		}

		bt_index_inc(&wake_index);
	}

	return NULL;
}

static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag)
{
	const int index = TAG_TO_INDEX(bt, tag);
	struct bt_wait_state *bs;

	/*
	 * The unlock memory barrier need to order access to req in free
	 * path and clearing tag bit
	 */
	clear_bit_unlock(TAG_TO_BIT(bt, tag), &bt->map[index].word);

	bs = bt_wake_ptr(bt);
	if (bs && atomic_dec_and_test(&bs->wait_cnt)) {
		atomic_set(&bs->wait_cnt, bt->wake_cnt);
		bt_index_inc(&bt->wake_index);
		wake_up(&bs->wait);
	}
}

static void __blk_mq_put_tag(struct blk_mq_tags *tags, unsigned int tag)
{
	BUG_ON(tag >= tags->nr_tags);

	bt_clear_tag(&tags->bitmap_tags, tag);
}

static void __blk_mq_put_reserved_tag(struct blk_mq_tags *tags,
				      unsigned int tag)
{
	BUG_ON(tag >= tags->nr_reserved_tags);

	bt_clear_tag(&tags->breserved_tags, tag);
}

void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag,
		    unsigned int *last_tag)
{
	struct blk_mq_tags *tags = hctx->tags;

	if (tag >= tags->nr_reserved_tags) {
		const int real_tag = tag - tags->nr_reserved_tags;

		__blk_mq_put_tag(tags, real_tag);
		*last_tag = real_tag;
	} else
		__blk_mq_put_reserved_tag(tags, tag);
}

static void bt_for_each_free(struct blk_mq_bitmap_tags *bt,
			     unsigned long *free_map, unsigned int off)
{
	int i;

	for (i = 0; i < bt->map_nr; i++) {
		struct blk_align_bitmap *bm = &bt->map[i];
		int bit = 0;

		do {
			bit = find_next_zero_bit(&bm->word, bm->depth, bit);
			if (bit >= bm->depth)
				break;

			__set_bit(bit + off, free_map);
			bit++;
		} while (1);

		off += (1 << bt->bits_per_word);
	}
}

void blk_mq_tag_busy_iter(struct blk_mq_tags *tags,
			  void (*fn)(void *, unsigned long *), void *data)
{
	unsigned long *tag_map;
	size_t map_size;

	map_size = ALIGN(tags->nr_tags, BITS_PER_LONG) / BITS_PER_LONG;
	tag_map = kzalloc(map_size * sizeof(unsigned long), GFP_ATOMIC);
	if (!tag_map)
		return;

	bt_for_each_free(&tags->bitmap_tags, tag_map, tags->nr_reserved_tags);
	if (tags->nr_reserved_tags)
		bt_for_each_free(&tags->breserved_tags, tag_map, 0);

	fn(data, tag_map);
	kfree(tag_map);
}
EXPORT_SYMBOL(blk_mq_tag_busy_iter);

static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt)
{
	unsigned int i, used;

	for (i = 0, used = 0; i < bt->map_nr; i++) {
		struct blk_align_bitmap *bm = &bt->map[i];

		used += bitmap_weight(&bm->word, bm->depth);
	}

	return bt->depth - used;
}

static void bt_update_count(struct blk_mq_bitmap_tags *bt,
			    unsigned int depth)
{
	unsigned int tags_per_word = 1U << bt->bits_per_word;
	unsigned int map_depth = depth;

	if (depth) {
		int i;

		for (i = 0; i < bt->map_nr; i++) {
			bt->map[i].depth = min(map_depth, tags_per_word);
			map_depth -= bt->map[i].depth;
		}
	}

	bt->wake_cnt = BT_WAIT_BATCH;
	if (bt->wake_cnt > depth / 4)
		bt->wake_cnt = max(1U, depth / 4);

	bt->depth = depth;
}

static int bt_alloc(struct blk_mq_bitmap_tags *bt, unsigned int depth,
			int node, bool reserved)
{
	int i;

	bt->bits_per_word = ilog2(BITS_PER_LONG);

	/*
	 * Depth can be zero for reserved tags, that's not a failure
	 * condition.
	 */
	if (depth) {
		unsigned int nr, tags_per_word;

		tags_per_word = (1 << bt->bits_per_word);

		/*
		 * If the tag space is small, shrink the number of tags
		 * per word so we spread over a few cachelines, at least.
		 * If less than 4 tags, just forget about it, it's not
		 * going to work optimally anyway.
		 */
		if (depth >= 4) {
			while (tags_per_word * 4 > depth) {
				bt->bits_per_word--;
				tags_per_word = (1 << bt->bits_per_word);
			}
		}

		nr = ALIGN(depth, tags_per_word) / tags_per_word;
		bt->map = kzalloc_node(nr * sizeof(struct blk_align_bitmap),
						GFP_KERNEL, node);
		if (!bt->map)
			return -ENOMEM;

		bt->map_nr = nr;
	}

	bt->bs = kzalloc(BT_WAIT_QUEUES * sizeof(*bt->bs), GFP_KERNEL);
	if (!bt->bs) {
		kfree(bt->map);
		return -ENOMEM;
	}

	for (i = 0; i < BT_WAIT_QUEUES; i++)
		init_waitqueue_head(&bt->bs[i].wait);

	bt_update_count(bt, depth);
	return 0;
}

static void bt_free(struct blk_mq_bitmap_tags *bt)
{
	kfree(bt->map);
	kfree(bt->bs);
}

static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
						   int node)
{
	unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;

	if (bt_alloc(&tags->bitmap_tags, depth, node, false))
		goto enomem;
	if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node, true))
		goto enomem;

	return tags;
enomem:
	bt_free(&tags->bitmap_tags);
	kfree(tags);
	return NULL;
}

struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
				     unsigned int reserved_tags, int node)
{
	struct blk_mq_tags *tags;

	if (total_tags > BLK_MQ_TAG_MAX) {
		pr_err("blk-mq: tag depth too large\n");
		return NULL;
	}

	tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
	if (!tags)
		return NULL;

	tags->nr_tags = total_tags;
	tags->nr_reserved_tags = reserved_tags;

	return blk_mq_init_bitmap_tags(tags, node);
}

void blk_mq_free_tags(struct blk_mq_tags *tags)
{
	bt_free(&tags->bitmap_tags);
	bt_free(&tags->breserved_tags);
	kfree(tags);
}

void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *tag)
{
	unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;

	*tag = prandom_u32() % depth;
}

int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth)
{
	tdepth -= tags->nr_reserved_tags;
	if (tdepth > tags->nr_tags)
		return -EINVAL;

	/*
	 * Don't need (or can't) update reserved tags here, they remain
	 * static and should never need resizing.
	 */
	bt_update_count(&tags->bitmap_tags, tdepth);
	blk_mq_tag_wakeup_all(tags);
	return 0;
}

ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page)
{
	char *orig_page = page;
	unsigned int free, res;

	if (!tags)
		return 0;

	page += sprintf(page, "nr_tags=%u, reserved_tags=%u, "
			"bits_per_word=%u\n",
			tags->nr_tags, tags->nr_reserved_tags,
			tags->bitmap_tags.bits_per_word);

	free = bt_unused_tags(&tags->bitmap_tags);
	res = bt_unused_tags(&tags->breserved_tags);

	page += sprintf(page, "nr_free=%u, nr_reserved=%u\n", free, res);
	page += sprintf(page, "active_queues=%u\n", atomic_read(&tags->active_queues));

	return page - orig_page;
}
Commit	Line	Data
75bb4625 JA	1	/*
	2	* Fast and scalable bitmap tagging variant. Uses sparser bitmaps spread
	3	* over multiple cachelines to avoid ping-pong between multiple submitters
	4	* or submitter and completer. Uses rolling wakeups to avoid falling of
	5	* the scaling cliff when we run out of tags and have to start putting
	6	* submitters to sleep.
	7	*
	8	* Uses active queue tracking to support fairer distribution of tags
	9	* between multiple submitters when a shared tag map is used.
	10	*
	11	* Copyright (C) 2013-2014 Jens Axboe
	12	*/
320ae51f JA	13	#include <linux/kernel.h>
320ae51f JA	14	#include <linux/module.h>
4bb659b1	15	#include <linux/random.h>
320ae51f JA	16
	17	#include <linux/blk-mq.h>
	18	#include "blk.h"
	19	#include "blk-mq.h"
	20	#include "blk-mq-tag.h"
	21
4bb659b1 JA	22	static bool bt_has_free_tags(struct blk_mq_bitmap_tags *bt)
	23	{
	24	int i;
	25
	26	for (i = 0; i < bt->map_nr; i++) {
e93ecf60	27	struct blk_align_bitmap *bm = &bt->map[i];
4bb659b1 JA	28	int ret;
	29
	30	ret = find_first_zero_bit(&bm->word, bm->depth);
	31	if (ret < bm->depth)
	32	return true;
	33	}
	34
	35	return false;
320ae51f JA	36	}
	37
	38	bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
	39	{
4bb659b1 JA	40	if (!tags)
	41	return true;
	42
	43	return bt_has_free_tags(&tags->bitmap_tags);
	44	}
	45
0d2602ca JA	46	static inline void bt_index_inc(unsigned int *index)
	47	{
	48	index = (index + 1) & (BT_WAIT_QUEUES - 1);
	49	}
	50
	51	/*
	52	* If a previously inactive queue goes active, bump the active user count.
	53	*/
	54	bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
	55	{
	56	if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
	57	!test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
	58	atomic_inc(&hctx->tags->active_queues);
	59
	60	return true;
	61	}
	62
	63	/*
e3a2b3f9	64	* Wakeup all potentially sleeping on normal (non-reserved) tags
0d2602ca	65	*/
e3a2b3f9	66	static void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags)
0d2602ca	67	{
0d2602ca JA	68	struct blk_mq_bitmap_tags *bt;
	69	int i, wake_index;
	70
0d2602ca JA	71	bt = &tags->bitmap_tags;
	72	wake_index = bt->wake_index;
	73	for (i = 0; i < BT_WAIT_QUEUES; i++) {
	74	struct bt_wait_state *bs = &bt->bs[wake_index];
	75
	76	if (waitqueue_active(&bs->wait))
	77	wake_up(&bs->wait);
	78
	79	bt_index_inc(&wake_index);
	80	}
	81	}
	82
e3a2b3f9 JA	83	/*
	84	* If a previously busy queue goes inactive, potential waiters could now
	85	* be allowed to queue. Wake them up and check.
	86	*/
	87	void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
	88	{
	89	struct blk_mq_tags *tags = hctx->tags;
	90
	91	if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
	92	return;
	93
	94	atomic_dec(&tags->active_queues);
	95
	96	blk_mq_tag_wakeup_all(tags);
	97	}
	98
0d2602ca JA	99	/*
	100	* For shared tag users, we track the number of currently active users
	101	* and attempt to provide a fair share of the tag depth for each of them.
	102	*/
	103	static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
	104	struct blk_mq_bitmap_tags *bt)
	105	{
	106	unsigned int depth, users;
	107
	108	if (!hctx \|\| !(hctx->flags & BLK_MQ_F_TAG_SHARED))
	109	return true;
	110	if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
	111	return true;
	112
	113	/*
	114	* Don't try dividing an ant
	115	*/
	116	if (bt->depth == 1)
	117	return true;
	118
	119	users = atomic_read(&hctx->tags->active_queues);
	120	if (!users)
	121	return true;
	122
	123	/*
	124	* Allow at least some tags
	125	*/
	126	depth = max((bt->depth + users - 1) / users, 4U);
	127	return atomic_read(&hctx->nr_active) < depth;
	128	}
	129
e93ecf60	130	static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
4bb659b1 JA	131	{
	132	int tag, org_last_tag, end;
	133
59d13bf5	134	org_last_tag = last_tag;
4bb659b1 JA	135	end = bm->depth;
	136	do {
	137	restart:
	138	tag = find_next_zero_bit(&bm->word, end, last_tag);
	139	if (unlikely(tag >= end)) {
	140	/*
	141	* We started with an offset, start from 0 to
	142	* exhaust the map.
	143	*/
	144	if (org_last_tag && last_tag) {
	145	end = last_tag;
	146	last_tag = 0;
	147	goto restart;
	148	}
	149	return -1;
	150	}
	151	last_tag = tag + 1;
	152	} while (test_and_set_bit_lock(tag, &bm->word));
	153
	154	return tag;
	155	}
	156
	157	/*
	158	* Straight forward bitmap tag implementation, where each bit is a tag
	159	* (cleared == free, and set == busy). The small twist is using per-cpu
	160	* last_tag caches, which blk-mq stores in the blk_mq_ctx software queue
	161	* contexts. This enables us to drastically limit the space searched,
	162	* without dirtying an extra shared cacheline like we would if we stored
	163	* the cache value inside the shared blk_mq_bitmap_tags structure. On top
	164	* of that, each word of tags is in a separate cacheline. This means that
	165	* multiple users will tend to stick to different cachelines, at least
	166	* until the map is exhausted.
	167	*/
0d2602ca JA	168	static int __bt_get(struct blk_mq_hw_ctx hctx, struct blk_mq_bitmap_tags bt,
0d2602ca JA	169	unsigned int *tag_cache)
4bb659b1 JA	170	{
	171	unsigned int last_tag, org_last_tag;
	172	int index, i, tag;
	173
0d2602ca JA	174	if (!hctx_may_queue(hctx, bt))
	175	return -1;
	176
4bb659b1	177	last_tag = org_last_tag = *tag_cache;
59d13bf5	178	index = TAG_TO_INDEX(bt, last_tag);
4bb659b1 JA	179
4bb659b1 JA	180	for (i = 0; i < bt->map_nr; i++) {
59d13bf5	181	tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag));
4bb659b1	182	if (tag != -1) {
59d13bf5	183	tag += (index << bt->bits_per_word);
4bb659b1 JA	184	goto done;
	185	}
	186
	187	last_tag = 0;
	188	if (++index >= bt->map_nr)
	189	index = 0;
	190	}
	191
	192	*tag_cache = 0;
	193	return -1;
	194
	195	/*
	196	* Only update the cache from the allocation path, if we ended
	197	* up using the specific cached tag.
	198	*/
	199	done:
	200	if (tag == org_last_tag) {
	201	last_tag = tag + 1;
	202	if (last_tag >= bt->depth - 1)
	203	last_tag = 0;
	204
	205	*tag_cache = last_tag;
	206	}
	207
	208	return tag;
	209	}
	210
4bb659b1 JA	211	static struct bt_wait_state bt_wait_ptr(struct blk_mq_bitmap_tags bt,
	212	struct blk_mq_hw_ctx *hctx)
	213	{
	214	struct bt_wait_state *bs;
	215
	216	if (!hctx)
	217	return &bt->bs[0];
	218
	219	bs = &bt->bs[hctx->wait_index];
	220	bt_index_inc(&hctx->wait_index);
	221	return bs;
320ae51f JA	222	}
320ae51f JA	223
4bb659b1 JA	224	static int bt_get(struct blk_mq_bitmap_tags bt, struct blk_mq_hw_ctx hctx,
4bb659b1 JA	225	unsigned int *last_tag, gfp_t gfp)
320ae51f	226	{
4bb659b1 JA	227	struct bt_wait_state *bs;
4bb659b1 JA	228	DEFINE_WAIT(wait);
320ae51f JA	229	int tag;
320ae51f JA	230
0d2602ca	231	tag = __bt_get(hctx, bt, last_tag);
4bb659b1 JA	232	if (tag != -1)
	233	return tag;
	234
	235	if (!(gfp & __GFP_WAIT))
	236	return -1;
	237
	238	bs = bt_wait_ptr(bt, hctx);
	239	do {
	240	bool was_empty;
	241
	242	was_empty = list_empty(&wait.task_list);
	243	prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE);
	244
0d2602ca	245	tag = __bt_get(hctx, bt, last_tag);
4bb659b1 JA	246	if (tag != -1)
	247	break;
	248
	249	if (was_empty)
	250	atomic_set(&bs->wait_cnt, bt->wake_cnt);
	251
	252	io_schedule();
	253	} while (1);
	254
	255	finish_wait(&bs->wait, &wait);
	256	return tag;
	257	}
	258
	259	static unsigned int __blk_mq_get_tag(struct blk_mq_tags *tags,
	260	struct blk_mq_hw_ctx *hctx,
	261	unsigned int *last_tag, gfp_t gfp)
	262	{
	263	int tag;
	264
	265	tag = bt_get(&tags->bitmap_tags, hctx, last_tag, gfp);
	266	if (tag >= 0)
	267	return tag + tags->nr_reserved_tags;
	268
	269	return BLK_MQ_TAG_FAIL;
320ae51f JA	270	}
	271
	272	static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_tags *tags,
	273	gfp_t gfp)
	274	{
4bb659b1	275	int tag, zero = 0;
320ae51f JA	276
	277	if (unlikely(!tags->nr_reserved_tags)) {
	278	WARN_ON_ONCE(1);
	279	return BLK_MQ_TAG_FAIL;
	280	}
	281
4bb659b1	282	tag = bt_get(&tags->breserved_tags, NULL, &zero, gfp);
320ae51f JA	283	if (tag < 0)
320ae51f JA	284	return BLK_MQ_TAG_FAIL;
4bb659b1	285
320ae51f JA	286	return tag;
	287	}
	288
0d2602ca	289	unsigned int blk_mq_get_tag(struct blk_mq_hw_ctx hctx, unsigned int last_tag,
4bb659b1	290	gfp_t gfp, bool reserved)
320ae51f JA	291	{
320ae51f JA	292	if (!reserved)
0d2602ca	293	return __blk_mq_get_tag(hctx->tags, hctx, last_tag, gfp);
320ae51f	294
0d2602ca	295	return __blk_mq_get_reserved_tag(hctx->tags, gfp);
320ae51f JA	296	}
320ae51f JA	297
4bb659b1 JA	298	static struct bt_wait_state bt_wake_ptr(struct blk_mq_bitmap_tags bt)
	299	{
	300	int i, wake_index;
	301
	302	wake_index = bt->wake_index;
	303	for (i = 0; i < BT_WAIT_QUEUES; i++) {
	304	struct bt_wait_state *bs = &bt->bs[wake_index];
	305
	306	if (waitqueue_active(&bs->wait)) {
	307	if (wake_index != bt->wake_index)
	308	bt->wake_index = wake_index;
	309
	310	return bs;
	311	}
	312
	313	bt_index_inc(&wake_index);
	314	}
	315
	316	return NULL;
	317	}
	318
	319	static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag)
	320	{
59d13bf5	321	const int index = TAG_TO_INDEX(bt, tag);
4bb659b1 JA	322	struct bt_wait_state *bs;
4bb659b1 JA	323
0289b2e1 ML	324	/*
	325	* The unlock memory barrier need to order access to req in free
	326	* path and clearing tag bit
	327	*/
	328	clear_bit_unlock(TAG_TO_BIT(bt, tag), &bt->map[index].word);
4bb659b1 JA	329
	330	bs = bt_wake_ptr(bt);
	331	if (bs && atomic_dec_and_test(&bs->wait_cnt)) {
4bb659b1 JA	332	atomic_set(&bs->wait_cnt, bt->wake_cnt);
	333	bt_index_inc(&bt->wake_index);
	334	wake_up(&bs->wait);
	335	}
	336	}
	337
320ae51f JA	338	static void __blk_mq_put_tag(struct blk_mq_tags *tags, unsigned int tag)
	339	{
	340	BUG_ON(tag >= tags->nr_tags);
	341
4bb659b1	342	bt_clear_tag(&tags->bitmap_tags, tag);
320ae51f JA	343	}
	344
	345	static void __blk_mq_put_reserved_tag(struct blk_mq_tags *tags,
	346	unsigned int tag)
	347	{
	348	BUG_ON(tag >= tags->nr_reserved_tags);
	349
4bb659b1	350	bt_clear_tag(&tags->breserved_tags, tag);
320ae51f JA	351	}
320ae51f JA	352
0d2602ca	353	void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag,
4bb659b1	354	unsigned int *last_tag)
320ae51f	355	{
0d2602ca JA	356	struct blk_mq_tags *tags = hctx->tags;
0d2602ca JA	357
4bb659b1 JA	358	if (tag >= tags->nr_reserved_tags) {
	359	const int real_tag = tag - tags->nr_reserved_tags;
	360
	361	__blk_mq_put_tag(tags, real_tag);
	362	*last_tag = real_tag;
	363	} else
320ae51f JA	364	__blk_mq_put_reserved_tag(tags, tag);
	365	}
	366
4bb659b1 JA	367	static void bt_for_each_free(struct blk_mq_bitmap_tags *bt,
4bb659b1 JA	368	unsigned long *free_map, unsigned int off)
320ae51f	369	{
4bb659b1 JA	370	int i;
	371
	372	for (i = 0; i < bt->map_nr; i++) {
e93ecf60	373	struct blk_align_bitmap *bm = &bt->map[i];
4bb659b1 JA	374	int bit = 0;
	375
	376	do {
	377	bit = find_next_zero_bit(&bm->word, bm->depth, bit);
	378	if (bit >= bm->depth)
	379	break;
	380
	381	__set_bit(bit + off, free_map);
	382	bit++;
	383	} while (1);
	384
59d13bf5	385	off += (1 << bt->bits_per_word);
4bb659b1	386	}
320ae51f JA	387	}
	388
	389	void blk_mq_tag_busy_iter(struct blk_mq_tags *tags,
	390	void (fn)(void , unsigned long ), void data)
	391	{
	392	unsigned long *tag_map;
	393	size_t map_size;
	394
	395	map_size = ALIGN(tags->nr_tags, BITS_PER_LONG) / BITS_PER_LONG;
	396	tag_map = kzalloc(map_size * sizeof(unsigned long), GFP_ATOMIC);
	397	if (!tag_map)
	398	return;
	399
4bb659b1	400	bt_for_each_free(&tags->bitmap_tags, tag_map, tags->nr_reserved_tags);
320ae51f	401	if (tags->nr_reserved_tags)
4bb659b1	402	bt_for_each_free(&tags->breserved_tags, tag_map, 0);
320ae51f JA	403
	404	fn(data, tag_map);
	405	kfree(tag_map);
	406	}
edf866b3	407	EXPORT_SYMBOL(blk_mq_tag_busy_iter);
320ae51f	408
4bb659b1 JA	409	static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt)
	410	{
	411	unsigned int i, used;
	412
	413	for (i = 0, used = 0; i < bt->map_nr; i++) {
e93ecf60	414	struct blk_align_bitmap *bm = &bt->map[i];
4bb659b1 JA	415
	416	used += bitmap_weight(&bm->word, bm->depth);
	417	}
	418
	419	return bt->depth - used;
	420	}
	421
e3a2b3f9 JA	422	static void bt_update_count(struct blk_mq_bitmap_tags *bt,
	423	unsigned int depth)
	424	{
	425	unsigned int tags_per_word = 1U << bt->bits_per_word;
	426	unsigned int map_depth = depth;
	427
	428	if (depth) {
	429	int i;
	430
	431	for (i = 0; i < bt->map_nr; i++) {
	432	bt->map[i].depth = min(map_depth, tags_per_word);
	433	map_depth -= bt->map[i].depth;
	434	}
	435	}
	436
	437	bt->wake_cnt = BT_WAIT_BATCH;
	438	if (bt->wake_cnt > depth / 4)
	439	bt->wake_cnt = max(1U, depth / 4);
	440
	441	bt->depth = depth;
	442	}
	443
4bb659b1 JA	444	static int bt_alloc(struct blk_mq_bitmap_tags *bt, unsigned int depth,
	445	int node, bool reserved)
	446	{
	447	int i;
	448
59d13bf5 JA	449	bt->bits_per_word = ilog2(BITS_PER_LONG);
59d13bf5 JA	450
4bb659b1 JA	451	/*
	452	* Depth can be zero for reserved tags, that's not a failure
	453	* condition.
	454	*/
	455	if (depth) {
e3a2b3f9	456	unsigned int nr, tags_per_word;
59d13bf5 JA	457
	458	tags_per_word = (1 << bt->bits_per_word);
	459
	460	/*
	461	* If the tag space is small, shrink the number of tags
	462	* per word so we spread over a few cachelines, at least.
	463	* If less than 4 tags, just forget about it, it's not
	464	* going to work optimally anyway.
	465	*/
	466	if (depth >= 4) {
	467	while (tags_per_word * 4 > depth) {
	468	bt->bits_per_word--;
	469	tags_per_word = (1 << bt->bits_per_word);
	470	}
	471	}
4bb659b1	472
59d13bf5	473	nr = ALIGN(depth, tags_per_word) / tags_per_word;
e93ecf60	474	bt->map = kzalloc_node(nr * sizeof(struct blk_align_bitmap),
4bb659b1 JA	475	GFP_KERNEL, node);
	476	if (!bt->map)
	477	return -ENOMEM;
	478
	479	bt->map_nr = nr;
4bb659b1 JA	480	}
	481
	482	bt->bs = kzalloc(BT_WAIT_QUEUES * sizeof(*bt->bs), GFP_KERNEL);
	483	if (!bt->bs) {
	484	kfree(bt->map);
	485	return -ENOMEM;
	486	}
	487
	488	for (i = 0; i < BT_WAIT_QUEUES; i++)
	489	init_waitqueue_head(&bt->bs[i].wait);
	490
e3a2b3f9	491	bt_update_count(bt, depth);
4bb659b1 JA	492	return 0;
	493	}
	494
	495	static void bt_free(struct blk_mq_bitmap_tags *bt)
	496	{
	497	kfree(bt->map);
	498	kfree(bt->bs);
	499	}
	500
	501	static struct blk_mq_tags blk_mq_init_bitmap_tags(struct blk_mq_tags tags,
	502	int node)
	503	{
	504	unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
	505
	506	if (bt_alloc(&tags->bitmap_tags, depth, node, false))
	507	goto enomem;
	508	if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node, true))
	509	goto enomem;
	510
	511	return tags;
	512	enomem:
	513	bt_free(&tags->bitmap_tags);
	514	kfree(tags);
	515	return NULL;
	516	}
	517
320ae51f JA	518	struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
	519	unsigned int reserved_tags, int node)
	520	{
320ae51f	521	struct blk_mq_tags *tags;
320ae51f JA	522
	523	if (total_tags > BLK_MQ_TAG_MAX) {
	524	pr_err("blk-mq: tag depth too large\n");
	525	return NULL;
	526	}
	527
	528	tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
	529	if (!tags)
	530	return NULL;
	531
320ae51f JA	532	tags->nr_tags = total_tags;
320ae51f JA	533	tags->nr_reserved_tags = reserved_tags;
320ae51f	534
4bb659b1	535	return blk_mq_init_bitmap_tags(tags, node);
320ae51f JA	536	}
	537
	538	void blk_mq_free_tags(struct blk_mq_tags *tags)
	539	{
4bb659b1 JA	540	bt_free(&tags->bitmap_tags);
4bb659b1 JA	541	bt_free(&tags->breserved_tags);
320ae51f JA	542	kfree(tags);
	543	}
	544
4bb659b1 JA	545	void blk_mq_tag_init_last_tag(struct blk_mq_tags tags, unsigned int tag)
	546	{
	547	unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
	548
9d3d21ae	549	*tag = prandom_u32() % depth;
4bb659b1 JA	550	}
4bb659b1 JA	551
e3a2b3f9 JA	552	int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth)
	553	{
	554	tdepth -= tags->nr_reserved_tags;
	555	if (tdepth > tags->nr_tags)
	556	return -EINVAL;
	557
	558	/*
	559	* Don't need (or can't) update reserved tags here, they remain
	560	* static and should never need resizing.
	561	*/
	562	bt_update_count(&tags->bitmap_tags, tdepth);
	563	blk_mq_tag_wakeup_all(tags);
	564	return 0;
	565	}
	566
320ae51f JA	567	ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags tags, char page)
	568	{
	569	char *orig_page = page;
4bb659b1	570	unsigned int free, res;
320ae51f JA	571
	572	if (!tags)
	573	return 0;
	574
59d13bf5 JA	575	page += sprintf(page, "nr_tags=%u, reserved_tags=%u, "
	576	"bits_per_word=%u\n",
	577	tags->nr_tags, tags->nr_reserved_tags,
	578	tags->bitmap_tags.bits_per_word);
320ae51f	579
4bb659b1 JA	580	free = bt_unused_tags(&tags->bitmap_tags);
4bb659b1 JA	581	res = bt_unused_tags(&tags->breserved_tags);
320ae51f	582
4bb659b1	583	page += sprintf(page, "nr_free=%u, nr_reserved=%u\n", free, res);
0d2602ca	584	page += sprintf(page, "active_queues=%u\n", atomic_read(&tags->active_queues));
320ae51f JA	585
	586	return page - orig_page;
	587	}