// SPDX-License-Identifier: GPL-2.0
/*
 * Tag allocation using scalable bitmaps. 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/slab.h>
#include <linux/mm.h>
#include <linux/kmemleak.h>

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

/*
 * Recalculate wakeup batch when tag is shared by hctx.
 */
static void blk_mq_update_wake_batch(struct blk_mq_tags *tags,
                unsigned int users)
{
        if (!users)
                return;

        sbitmap_queue_recalculate_wake_batch(&tags->bitmap_tags,
                        users);
        sbitmap_queue_recalculate_wake_batch(&tags->breserved_tags,
                        users);
}

/*
 * If a previously inactive queue goes active, bump the active user count.
 * We need to do this before try to allocate driver tag, then even if fail
 * to get tag when first time, the other shared-tag users could reserve
 * budget for it.
 */
void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
{
        unsigned int users;
        unsigned long flags;
        struct blk_mq_tags *tags = hctx->tags;

        /*
         * calling test_bit() prior to test_and_set_bit() is intentional,
         * it avoids dirtying the cacheline if the queue is already active.
         */
        if (blk_mq_is_shared_tags(hctx->flags)) {
                struct request_queue *q = hctx->queue;

                if (test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) ||
                    test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
                        return;
        } else {
                if (test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) ||
                    test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
                        return;
        }

        spin_lock_irqsave(&tags->lock, flags);
        users = tags->active_queues + 1;
        WRITE_ONCE(tags->active_queues, users);
        blk_mq_update_wake_batch(tags, users);
        spin_unlock_irqrestore(&tags->lock, flags);
}

/*
 * Wakeup all potentially sleeping on tags
 */
void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
{
        sbitmap_queue_wake_all(&tags->bitmap_tags);
        if (include_reserve)
                sbitmap_queue_wake_all(&tags->breserved_tags);
}

/*
 * 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;
        unsigned int users;

        if (blk_mq_is_shared_tags(hctx->flags)) {
                struct request_queue *q = hctx->queue;

                if (!test_and_clear_bit(QUEUE_FLAG_HCTX_ACTIVE,
                                        &q->queue_flags))
                        return;
        } else {
                if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
                        return;
        }

        spin_lock_irq(&tags->lock);
        users = tags->active_queues - 1;
        WRITE_ONCE(tags->active_queues, users);
        blk_mq_update_wake_batch(tags, users);
        spin_unlock_irq(&tags->lock);

        blk_mq_tag_wakeup_all(tags, false);
}

static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
                            struct sbitmap_queue *bt)
{
        if (!data->q->elevator && !(data->flags & BLK_MQ_REQ_RESERVED) &&
                        !hctx_may_queue(data->hctx, bt))
                return BLK_MQ_NO_TAG;

        if (data->shallow_depth)
                return sbitmap_queue_get_shallow(bt, data->shallow_depth);
        else
                return __sbitmap_queue_get(bt);
}

unsigned long blk_mq_get_tags(struct blk_mq_alloc_data *data, int nr_tags,
                              unsigned int *offset)
{
        struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
        struct sbitmap_queue *bt = &tags->bitmap_tags;
        unsigned long ret;

        if (data->shallow_depth ||data->flags & BLK_MQ_REQ_RESERVED ||
            data->hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
                return 0;
        ret = __sbitmap_queue_get_batch(bt, nr_tags, offset);
        *offset += tags->nr_reserved_tags;
        return ret;
}

unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
{
        struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
        struct sbitmap_queue *bt;
        struct sbq_wait_state *ws;
        DEFINE_SBQ_WAIT(wait);
        unsigned int tag_offset;
        int tag;

        if (data->flags & BLK_MQ_REQ_RESERVED) {
                if (unlikely(!tags->nr_reserved_tags)) {
                        WARN_ON_ONCE(1);
                        return BLK_MQ_NO_TAG;
                }
                bt = &tags->breserved_tags;
                tag_offset = 0;
        } else {
                bt = &tags->bitmap_tags;
                tag_offset = tags->nr_reserved_tags;
        }

        tag = __blk_mq_get_tag(data, bt);
        if (tag != BLK_MQ_NO_TAG)
                goto found_tag;

        if (data->flags & BLK_MQ_REQ_NOWAIT)
                return BLK_MQ_NO_TAG;

        ws = bt_wait_ptr(bt, data->hctx);
        do {
                struct sbitmap_queue *bt_prev;

                /*
                 * We're out of tags on this hardware queue, kick any
                 * pending IO submits before going to sleep waiting for
                 * some to complete.
                 */
                blk_mq_run_hw_queue(data->hctx, false);

                /*
                 * Retry tag allocation after running the hardware queue,
                 * as running the queue may also have found completions.
                 */
                tag = __blk_mq_get_tag(data, bt);
                if (tag != BLK_MQ_NO_TAG)
                        break;

                sbitmap_prepare_to_wait(bt, ws, &wait, TASK_UNINTERRUPTIBLE);

                tag = __blk_mq_get_tag(data, bt);
                if (tag != BLK_MQ_NO_TAG)
                        break;

                bt_prev = bt;
                io_schedule();

                sbitmap_finish_wait(bt, ws, &wait);

                data->ctx = blk_mq_get_ctx(data->q);
                data->hctx = blk_mq_map_queue(data->cmd_flags, data->ctx);
                tags = blk_mq_tags_from_data(data);
                if (data->flags & BLK_MQ_REQ_RESERVED)
                        bt = &tags->breserved_tags;
                else
                        bt = &tags->bitmap_tags;

                /*
                 * If destination hw queue is changed, fake wake up on
                 * previous queue for compensating the wake up miss, so
                 * other allocations on previous queue won't be starved.
                 */
                if (bt != bt_prev)
                        sbitmap_queue_wake_up(bt_prev, 1);

                ws = bt_wait_ptr(bt, data->hctx);
        } while (1);

        sbitmap_finish_wait(bt, ws, &wait);

found_tag:
        /*
         * Give up this allocation if the hctx is inactive.  The caller will
         * retry on an active hctx.
         */
        if (unlikely(test_bit(BLK_MQ_S_INACTIVE, &data->hctx->state))) {
                blk_mq_put_tag(tags, data->ctx, tag + tag_offset);
                return BLK_MQ_NO_TAG;
        }
        return tag + tag_offset;
}

void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx,
                    unsigned int tag)
{
        if (!blk_mq_tag_is_reserved(tags, tag)) {
                const int real_tag = tag - tags->nr_reserved_tags;

                BUG_ON(real_tag >= tags->nr_tags);
                sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
        } else {
                sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
        }
}

void blk_mq_put_tags(struct blk_mq_tags *tags, int *tag_array, int nr_tags)
{
        sbitmap_queue_clear_batch(&tags->bitmap_tags, tags->nr_reserved_tags,
                                        tag_array, nr_tags);
}

struct bt_iter_data {
        struct blk_mq_hw_ctx *hctx;
        struct request_queue *q;
        busy_tag_iter_fn *fn;
        void *data;
        bool reserved;
};

static struct request *blk_mq_find_and_get_req(struct blk_mq_tags *tags,
                unsigned int bitnr)
{
        struct request *rq;

        rq = tags->rqs[bitnr];
        if (!rq || rq->tag != bitnr || !req_ref_inc_not_zero(rq))
                rq = NULL;
        return rq;
}

static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
{
        struct bt_iter_data *iter_data = data;
        struct blk_mq_hw_ctx *hctx = iter_data->hctx;
        struct request_queue *q = iter_data->q;
        struct blk_mq_tag_set *set = q->tag_set;
        struct blk_mq_tags *tags;
        struct request *rq;
        bool ret = true;

        if (blk_mq_is_shared_tags(set->flags))
                tags = set->shared_tags;
        else
                tags = hctx->tags;

        if (!iter_data->reserved)
                bitnr += tags->nr_reserved_tags;
        /*
         * We can hit rq == NULL here, because the tagging functions
         * test and set the bit before assigning ->rqs[].
         */
        rq = blk_mq_find_and_get_req(tags, bitnr);
        if (!rq)
                return true;

        if (rq->q == q && (!hctx || rq->mq_hctx == hctx))
                ret = iter_data->fn(rq, iter_data->data);
        blk_mq_put_rq_ref(rq);
        return ret;
}

/**
 * bt_for_each - iterate over the requests associated with a hardware queue
 * @hctx:       Hardware queue to examine.
 * @q:          Request queue @hctx is associated with (@hctx->queue).
 * @bt:         sbitmap to examine. This is either the breserved_tags member
 *              or the bitmap_tags member of struct blk_mq_tags.
 * @fn:         Pointer to the function that will be called for each request
 *              associated with @hctx that has been assigned a driver tag.
 *              @fn will be called as follows: @fn(rq, @data) where rq is a
 *              pointer to a request. Return %true to continue iterating tags;
 *              %false to stop.
 * @data:       Will be passed as second argument to @fn.
 * @reserved:   Indicates whether @bt is the breserved_tags member or the
 *              bitmap_tags member of struct blk_mq_tags.
 */
static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct request_queue *q,
                        struct sbitmap_queue *bt, busy_tag_iter_fn *fn,
                        void *data, bool reserved)
{
        struct bt_iter_data iter_data = {
                .hctx = hctx,
                .fn = fn,
                .data = data,
                .reserved = reserved,
                .q = q,
        };

        sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
}

struct bt_tags_iter_data {
        struct blk_mq_tags *tags;
        busy_tag_iter_fn *fn;
        void *data;
        unsigned int flags;
};

#define BT_TAG_ITER_RESERVED            (1 << 0)
#define BT_TAG_ITER_STARTED             (1 << 1)
#define BT_TAG_ITER_STATIC_RQS          (1 << 2)

static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
{
        struct bt_tags_iter_data *iter_data = data;
        struct blk_mq_tags *tags = iter_data->tags;
        struct request *rq;
        bool ret = true;
        bool iter_static_rqs = !!(iter_data->flags & BT_TAG_ITER_STATIC_RQS);

        if (!(iter_data->flags & BT_TAG_ITER_RESERVED))
                bitnr += tags->nr_reserved_tags;

        /*
         * We can hit rq == NULL here, because the tagging functions
         * test and set the bit before assigning ->rqs[].
         */
        if (iter_static_rqs)
                rq = tags->static_rqs[bitnr];
        else
                rq = blk_mq_find_and_get_req(tags, bitnr);
        if (!rq)
                return true;

        if (!(iter_data->flags & BT_TAG_ITER_STARTED) ||
            blk_mq_request_started(rq))
                ret = iter_data->fn(rq, iter_data->data);
        if (!iter_static_rqs)
                blk_mq_put_rq_ref(rq);
        return ret;
}

/**
 * bt_tags_for_each - iterate over the requests in a tag map
 * @tags:       Tag map to iterate over.
 * @bt:         sbitmap to examine. This is either the breserved_tags member
 *              or the bitmap_tags member of struct blk_mq_tags.
 * @fn:         Pointer to the function that will be called for each started
 *              request. @fn will be called as follows: @fn(rq, @data) where rq
 *              is a pointer to a request. Return %true to continue iterating
 *              tags; %false to stop.
 * @data:       Will be passed as second argument to @fn.
 * @flags:      BT_TAG_ITER_*
 */
static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
                             busy_tag_iter_fn *fn, void *data, unsigned int flags)
{
        struct bt_tags_iter_data iter_data = {
                .tags = tags,
                .fn = fn,
                .data = data,
                .flags = flags,
        };

        if (tags->rqs)
                sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
}

static void __blk_mq_all_tag_iter(struct blk_mq_tags *tags,
                busy_tag_iter_fn *fn, void *priv, unsigned int flags)
{
        WARN_ON_ONCE(flags & BT_TAG_ITER_RESERVED);

        if (tags->nr_reserved_tags)
                bt_tags_for_each(tags, &tags->breserved_tags, fn, priv,
                                 flags | BT_TAG_ITER_RESERVED);
        bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, flags);
}

/**
 * blk_mq_all_tag_iter - iterate over all requests in a tag map
 * @tags:       Tag map to iterate over.
 * @fn:         Pointer to the function that will be called for each
 *              request. @fn will be called as follows: @fn(rq, @priv) where rq
 *              is a pointer to a request. Return %true to continue iterating
 *              tags; %false to stop.
 * @priv:       Will be passed as second argument to @fn.
 *
 * Caller has to pass the tag map from which requests are allocated.
 */
void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
                void *priv)
{
        __blk_mq_all_tag_iter(tags, fn, priv, BT_TAG_ITER_STATIC_RQS);
}

/**
 * blk_mq_tagset_busy_iter - iterate over all started requests in a tag set
 * @tagset:     Tag set to iterate over.
 * @fn:         Pointer to the function that will be called for each started
 *              request. @fn will be called as follows: @fn(rq, @priv) where
 *              rq is a pointer to a request. Return true to continue iterating
 *              tags, false to stop.
 * @priv:       Will be passed as second argument to @fn.
 *
 * We grab one request reference before calling @fn and release it after
 * @fn returns.
 */
void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
                busy_tag_iter_fn *fn, void *priv)
{
        unsigned int flags = tagset->flags;
        int i, nr_tags, srcu_idx;

        srcu_idx = srcu_read_lock(&tagset->tags_srcu);

        nr_tags = blk_mq_is_shared_tags(flags) ? 1 : tagset->nr_hw_queues;

        for (i = 0; i < nr_tags; i++) {
                if (tagset->tags && tagset->tags[i])
                        __blk_mq_all_tag_iter(tagset->tags[i], fn, priv,
                                              BT_TAG_ITER_STARTED);
        }
        srcu_read_unlock(&tagset->tags_srcu, srcu_idx);
}
EXPORT_SYMBOL(blk_mq_tagset_busy_iter);

static bool blk_mq_tagset_count_completed_rqs(struct request *rq, void *data)
{
        unsigned *count = data;

        if (blk_mq_request_completed(rq))
                (*count)++;
        return true;
}

/**
 * blk_mq_tagset_wait_completed_request - Wait until all scheduled request
 * completions have finished.
 * @tagset:     Tag set to drain completed request
 *
 * Note: This function has to be run after all IO queues are shutdown
 */
void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set *tagset)
{
        while (true) {
                unsigned count = 0;

                blk_mq_tagset_busy_iter(tagset,
                                blk_mq_tagset_count_completed_rqs, &count);
                if (!count)
                        break;
                msleep(5);
        }
}
EXPORT_SYMBOL(blk_mq_tagset_wait_completed_request);

/**
 * blk_mq_queue_tag_busy_iter - iterate over all requests with a driver tag
 * @q:          Request queue to examine.
 * @fn:         Pointer to the function that will be called for each request
 *              on @q. @fn will be called as follows: @fn(rq, @priv) where rq
 *              is a pointer to a request and hctx points to the hardware queue
 *              associated with the request.
 * @priv:       Will be passed as second argument to @fn.
 *
 * Note: if @q->tag_set is shared with other request queues then @fn will be
 * called for all requests on all queues that share that tag set and not only
 * for requests associated with @q.
 */
void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_tag_iter_fn *fn,
                void *priv)
{
        int srcu_idx;

        /*
         * __blk_mq_update_nr_hw_queues() updates nr_hw_queues and queue_hw_ctx
         * while the queue is frozen. So we can use q_usage_counter to avoid
         * racing with it.
         */
        if (!percpu_ref_tryget(&q->q_usage_counter))
                return;

        srcu_idx = srcu_read_lock(&q->tag_set->tags_srcu);
        if (blk_mq_is_shared_tags(q->tag_set->flags)) {
                struct blk_mq_tags *tags = q->tag_set->shared_tags;
                struct sbitmap_queue *bresv = &tags->breserved_tags;
                struct sbitmap_queue *btags = &tags->bitmap_tags;

                if (tags->nr_reserved_tags)
                        bt_for_each(NULL, q, bresv, fn, priv, true);
                bt_for_each(NULL, q, btags, fn, priv, false);
        } else {
                struct blk_mq_hw_ctx *hctx;
                unsigned long i;

                queue_for_each_hw_ctx(q, hctx, i) {
                        struct blk_mq_tags *tags = hctx->tags;
                        struct sbitmap_queue *bresv = &tags->breserved_tags;
                        struct sbitmap_queue *btags = &tags->bitmap_tags;

                        /*
                         * If no software queues are currently mapped to this
                         * hardware queue, there's nothing to check
                         */
                        if (!blk_mq_hw_queue_mapped(hctx))
                                continue;

                        if (tags->nr_reserved_tags)
                                bt_for_each(hctx, q, bresv, fn, priv, true);
                        bt_for_each(hctx, q, btags, fn, priv, false);
                }
        }
        srcu_read_unlock(&q->tag_set->tags_srcu, srcu_idx);
        blk_queue_exit(q);
}

static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
                    bool round_robin, int node)
{
        return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
                                       node);
}

struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
                unsigned int reserved_tags, unsigned int flags, int node)
{
        unsigned int depth = total_tags - reserved_tags;
        bool round_robin = flags & BLK_MQ_F_TAG_RR;
        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;
        spin_lock_init(&tags->lock);
        INIT_LIST_HEAD(&tags->page_list);

        if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
                goto out_free_tags;
        if (bt_alloc(&tags->breserved_tags, reserved_tags, round_robin, node))
                goto out_free_bitmap_tags;

        return tags;

out_free_bitmap_tags:
        sbitmap_queue_free(&tags->bitmap_tags);
out_free_tags:
        kfree(tags);
        return NULL;
}

static void blk_mq_free_tags_callback(struct rcu_head *head)
{
        struct blk_mq_tags *tags = container_of(head, struct blk_mq_tags,
                                                rcu_head);
        struct page *page;

        while (!list_empty(&tags->page_list)) {
                page = list_first_entry(&tags->page_list, struct page, lru);
                list_del_init(&page->lru);
                /*
                 * Remove kmemleak object previously allocated in
                 * blk_mq_alloc_rqs().
                 */
                kmemleak_free(page_address(page));
                __free_pages(page, page->private);
        }
        kfree(tags);
}

void blk_mq_free_tags(struct blk_mq_tag_set *set, struct blk_mq_tags *tags)
{
        sbitmap_queue_free(&tags->bitmap_tags);
        sbitmap_queue_free(&tags->breserved_tags);

        /* if tags pages is not allocated yet, free tags directly */
        if (list_empty(&tags->page_list)) {
                kfree(tags);
                return;
        }

        call_srcu(&set->tags_srcu, &tags->rcu_head, blk_mq_free_tags_callback);
}

void blk_mq_tag_resize_shared_tags(struct blk_mq_tag_set *set, unsigned int size)
{
        struct blk_mq_tags *tags = set->shared_tags;

        sbitmap_queue_resize(&tags->bitmap_tags, size - set->reserved_tags);
}

void blk_mq_tag_update_sched_shared_tags(struct request_queue *q,
                                         unsigned int nr)
{
        sbitmap_queue_resize(&q->sched_shared_tags->bitmap_tags,
                             nr - q->tag_set->reserved_tags);
}

/**
 * blk_mq_unique_tag() - return a tag that is unique queue-wide
 * @rq: request for which to compute a unique tag
 *
 * The tag field in struct request is unique per hardware queue but not over
 * all hardware queues. Hence this function that returns a tag with the
 * hardware context index in the upper bits and the per hardware queue tag in
 * the lower bits.
 *
 * Note: When called for a request that is queued on a non-multiqueue request
 * queue, the hardware context index is set to zero.
 */
u32 blk_mq_unique_tag(struct request *rq)
{
        return (rq->mq_hctx->queue_num << BLK_MQ_UNIQUE_TAG_BITS) |
                (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
}
EXPORT_SYMBOL(blk_mq_unique_tag);