/*
 * Functions related to sysfs handling
 */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/blktrace_api.h>
#include <linux/blk-mq.h>
#include <linux/blk-cgroup.h>

#include "blk.h"
#include "blk-mq.h"
#include "blk-mq-debugfs.h"
#include "blk-wbt.h"

struct queue_sysfs_entry {
        struct attribute attr;
        ssize_t (*show)(struct request_queue *, char *);
        ssize_t (*store)(struct request_queue *, const char *, size_t);
};

static ssize_t
queue_var_show(unsigned long var, char *page)
{
        return sprintf(page, "%lu\n", var);
}

static ssize_t
queue_var_store(unsigned long *var, const char *page, size_t count)
{
        int err;
        unsigned long v;

        err = kstrtoul(page, 10, &v);
        if (err || v > UINT_MAX)
                return -EINVAL;

        *var = v;

        return count;
}

static ssize_t queue_var_store64(s64 *var, const char *page)
{
        int err;
        s64 v;

        err = kstrtos64(page, 10, &v);
        if (err < 0)
                return err;

        *var = v;
        return 0;
}

static ssize_t queue_requests_show(struct request_queue *q, char *page)
{
        return queue_var_show(q->nr_requests, (page));
}

static ssize_t
queue_requests_store(struct request_queue *q, const char *page, size_t count)
{
        unsigned long nr;
        int ret, err;

        if (!q->request_fn && !q->mq_ops)
                return -EINVAL;

        ret = queue_var_store(&nr, page, count);
        if (ret < 0)
                return ret;

        if (nr < BLKDEV_MIN_RQ)
                nr = BLKDEV_MIN_RQ;

        if (q->request_fn)
                err = blk_update_nr_requests(q, nr);
        else
                err = blk_mq_update_nr_requests(q, nr);

        if (err)
                return err;

        return ret;
}

static ssize_t queue_ra_show(struct request_queue *q, char *page)
{
        unsigned long ra_kb = q->backing_dev_info->ra_pages <<
                                        (PAGE_SHIFT - 10);

        return queue_var_show(ra_kb, (page));
}

static ssize_t
queue_ra_store(struct request_queue *q, const char *page, size_t count)
{
        unsigned long ra_kb;
        ssize_t ret = queue_var_store(&ra_kb, page, count);

        if (ret < 0)
                return ret;

        q->backing_dev_info->ra_pages = ra_kb >> (PAGE_SHIFT - 10);

        return ret;
}

static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
{
        int max_sectors_kb = queue_max_sectors(q) >> 1;

        return queue_var_show(max_sectors_kb, (page));
}

static ssize_t queue_max_segments_show(struct request_queue *q, char *page)
{
        return queue_var_show(queue_max_segments(q), (page));
}

static ssize_t queue_max_discard_segments_show(struct request_queue *q,
                char *page)
{
        return queue_var_show(queue_max_discard_segments(q), (page));
}

static ssize_t queue_max_integrity_segments_show(struct request_queue *q, char *page)
{
        return queue_var_show(q->limits.max_integrity_segments, (page));
}

static ssize_t queue_max_segment_size_show(struct request_queue *q, char *page)
{
        if (blk_queue_cluster(q))
                return queue_var_show(queue_max_segment_size(q), (page));

        return queue_var_show(PAGE_SIZE, (page));
}

static ssize_t queue_logical_block_size_show(struct request_queue *q, char *page)
{
        return queue_var_show(queue_logical_block_size(q), page);
}

static ssize_t queue_physical_block_size_show(struct request_queue *q, char *page)
{
        return queue_var_show(queue_physical_block_size(q), page);
}

static ssize_t queue_chunk_sectors_show(struct request_queue *q, char *page)
{
        return queue_var_show(q->limits.chunk_sectors, page);
}

static ssize_t queue_io_min_show(struct request_queue *q, char *page)
{
        return queue_var_show(queue_io_min(q), page);
}

static ssize_t queue_io_opt_show(struct request_queue *q, char *page)
{
        return queue_var_show(queue_io_opt(q), page);
}

static ssize_t queue_discard_granularity_show(struct request_queue *q, char *page)
{
        return queue_var_show(q->limits.discard_granularity, page);
}

static ssize_t queue_discard_max_hw_show(struct request_queue *q, char *page)
{

        return sprintf(page, "%llu\n",
                (unsigned long long)q->limits.max_hw_discard_sectors << 9);
}

static ssize_t queue_discard_max_show(struct request_queue *q, char *page)
{
        return sprintf(page, "%llu\n",
                       (unsigned long long)q->limits.max_discard_sectors << 9);
}

static ssize_t queue_discard_max_store(struct request_queue *q,
                                       const char *page, size_t count)
{
        unsigned long max_discard;
        ssize_t ret = queue_var_store(&max_discard, page, count);

        if (ret < 0)
                return ret;

        if (max_discard & (q->limits.discard_granularity - 1))
                return -EINVAL;

        max_discard >>= 9;
        if (max_discard > UINT_MAX)
                return -EINVAL;

        if (max_discard > q->limits.max_hw_discard_sectors)
                max_discard = q->limits.max_hw_discard_sectors;

        q->limits.max_discard_sectors = max_discard;
        return ret;
}

static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *page)
{
        return queue_var_show(0, page);
}

static ssize_t queue_write_same_max_show(struct request_queue *q, char *page)
{
        return sprintf(page, "%llu\n",
                (unsigned long long)q->limits.max_write_same_sectors << 9);
}

static ssize_t queue_write_zeroes_max_show(struct request_queue *q, char *page)
{
        return sprintf(page, "%llu\n",
                (unsigned long long)q->limits.max_write_zeroes_sectors << 9);
}

static ssize_t
queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
{
        unsigned long max_sectors_kb,
                max_hw_sectors_kb = queue_max_hw_sectors(q) >> 1,
                        page_kb = 1 << (PAGE_SHIFT - 10);
        ssize_t ret = queue_var_store(&max_sectors_kb, page, count);

        if (ret < 0)
                return ret;

        max_hw_sectors_kb = min_not_zero(max_hw_sectors_kb, (unsigned long)
                                         q->limits.max_dev_sectors >> 1);

        if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
                return -EINVAL;

        spin_lock_irq(q->queue_lock);
        q->limits.max_sectors = max_sectors_kb << 1;
        q->backing_dev_info->io_pages = max_sectors_kb >> (PAGE_SHIFT - 10);
        spin_unlock_irq(q->queue_lock);

        return ret;
}

static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
{
        int max_hw_sectors_kb = queue_max_hw_sectors(q) >> 1;

        return queue_var_show(max_hw_sectors_kb, (page));
}

#define QUEUE_SYSFS_BIT_FNS(name, flag, neg)                            \
static ssize_t                                                          \
queue_show_##name(struct request_queue *q, char *page)                  \
{                                                                       \
        int bit;                                                        \
        bit = test_bit(QUEUE_FLAG_##flag, &q->queue_flags);             \
        return queue_var_show(neg ? !bit : bit, page);                  \
}                                                                       \
static ssize_t                                                          \
queue_store_##name(struct request_queue *q, const char *page, size_t count) \
{                                                                       \
        unsigned long val;                                              \
        ssize_t ret;                                                    \
        ret = queue_var_store(&val, page, count);                       \
        if (ret < 0)                                                    \
                 return ret;                                            \
        if (neg)                                                        \
                val = !val;                                             \
                                                                        \
        spin_lock_irq(q->queue_lock);                                   \
        if (val)                                                        \
                queue_flag_set(QUEUE_FLAG_##flag, q);                   \
        else                                                            \
                queue_flag_clear(QUEUE_FLAG_##flag, q);                 \
        spin_unlock_irq(q->queue_lock);                                 \
        return ret;                                                     \
}

QUEUE_SYSFS_BIT_FNS(nonrot, NONROT, 1);
QUEUE_SYSFS_BIT_FNS(random, ADD_RANDOM, 0);
QUEUE_SYSFS_BIT_FNS(iostats, IO_STAT, 0);
#undef QUEUE_SYSFS_BIT_FNS

static ssize_t queue_zoned_show(struct request_queue *q, char *page)
{
        switch (blk_queue_zoned_model(q)) {
        case BLK_ZONED_HA:
                return sprintf(page, "host-aware\n");
        case BLK_ZONED_HM:
                return sprintf(page, "host-managed\n");
        default:
                return sprintf(page, "none\n");
        }
}

static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
{
        return queue_var_show((blk_queue_nomerges(q) << 1) |
                               blk_queue_noxmerges(q), page);
}

static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
                                    size_t count)
{
        unsigned long nm;
        ssize_t ret = queue_var_store(&nm, page, count);

        if (ret < 0)
                return ret;

        spin_lock_irq(q->queue_lock);
        queue_flag_clear(QUEUE_FLAG_NOMERGES, q);
        queue_flag_clear(QUEUE_FLAG_NOXMERGES, q);
        if (nm == 2)
                queue_flag_set(QUEUE_FLAG_NOMERGES, q);
        else if (nm)
                queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
        spin_unlock_irq(q->queue_lock);

        return ret;
}

static ssize_t queue_rq_affinity_show(struct request_queue *q, char *page)
{
        bool set = test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags);
        bool force = test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags);

        return queue_var_show(set << force, page);
}

static ssize_t
queue_rq_affinity_store(struct request_queue *q, const char *page, size_t count)
{
        ssize_t ret = -EINVAL;
#ifdef CONFIG_SMP
        unsigned long val;

        ret = queue_var_store(&val, page, count);
        if (ret < 0)
                return ret;

        spin_lock_irq(q->queue_lock);
        if (val == 2) {
                queue_flag_set(QUEUE_FLAG_SAME_COMP, q);
                queue_flag_set(QUEUE_FLAG_SAME_FORCE, q);
        } else if (val == 1) {
                queue_flag_set(QUEUE_FLAG_SAME_COMP, q);
                queue_flag_clear(QUEUE_FLAG_SAME_FORCE, q);
        } else if (val == 0) {
                queue_flag_clear(QUEUE_FLAG_SAME_COMP, q);
                queue_flag_clear(QUEUE_FLAG_SAME_FORCE, q);
        }
        spin_unlock_irq(q->queue_lock);
#endif
        return ret;
}

static ssize_t queue_poll_delay_show(struct request_queue *q, char *page)
{
        int val;

        if (q->poll_nsec == -1)
                val = -1;
        else
                val = q->poll_nsec / 1000;

        return sprintf(page, "%d\n", val);
}

static ssize_t queue_poll_delay_store(struct request_queue *q, const char *page,
                                size_t count)
{
        int err, val;

        if (!q->mq_ops || !q->mq_ops->poll)
                return -EINVAL;

        err = kstrtoint(page, 10, &val);
        if (err < 0)
                return err;

        if (val == -1)
                q->poll_nsec = -1;
        else
                q->poll_nsec = val * 1000;

        return count;
}

static ssize_t queue_poll_show(struct request_queue *q, char *page)
{
        return queue_var_show(test_bit(QUEUE_FLAG_POLL, &q->queue_flags), page);
}

static ssize_t queue_poll_store(struct request_queue *q, const char *page,
                                size_t count)
{
        unsigned long poll_on;
        ssize_t ret;

        if (!q->mq_ops || !q->mq_ops->poll)
                return -EINVAL;

        ret = queue_var_store(&poll_on, page, count);
        if (ret < 0)
                return ret;

        spin_lock_irq(q->queue_lock);
        if (poll_on)
                queue_flag_set(QUEUE_FLAG_POLL, q);
        else
                queue_flag_clear(QUEUE_FLAG_POLL, q);
        spin_unlock_irq(q->queue_lock);

        return ret;
}

static ssize_t queue_wb_lat_show(struct request_queue *q, char *page)
{
        if (!q->rq_wb)
                return -EINVAL;

        return sprintf(page, "%llu\n", div_u64(q->rq_wb->min_lat_nsec, 1000));
}

static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
                                  size_t count)
{
        struct rq_wb *rwb;
        ssize_t ret;
        s64 val;

        ret = queue_var_store64(&val, page);
        if (ret < 0)
                return ret;
        if (val < -1)
                return -EINVAL;

        rwb = q->rq_wb;
        if (!rwb) {
                ret = wbt_init(q);
                if (ret)
                        return ret;

                rwb = q->rq_wb;
                if (!rwb)
                        return -EINVAL;
        }

        if (val == -1)
                rwb->min_lat_nsec = wbt_default_latency_nsec(q);
        else if (val >= 0)
                rwb->min_lat_nsec = val * 1000ULL;

        if (rwb->enable_state == WBT_STATE_ON_DEFAULT)
                rwb->enable_state = WBT_STATE_ON_MANUAL;

        wbt_update_limits(rwb);
        return count;
}

static ssize_t queue_wc_show(struct request_queue *q, char *page)
{
        if (test_bit(QUEUE_FLAG_WC, &q->queue_flags))
                return sprintf(page, "write back\n");

        return sprintf(page, "write through\n");
}

static ssize_t queue_wc_store(struct request_queue *q, const char *page,
                              size_t count)
{
        int set = -1;

        if (!strncmp(page, "write back", 10))
                set = 1;
        else if (!strncmp(page, "write through", 13) ||
                 !strncmp(page, "none", 4))
                set = 0;

        if (set == -1)
                return -EINVAL;

        spin_lock_irq(q->queue_lock);
        if (set)
                queue_flag_set(QUEUE_FLAG_WC, q);
        else
                queue_flag_clear(QUEUE_FLAG_WC, q);
        spin_unlock_irq(q->queue_lock);

        return count;
}

static ssize_t queue_dax_show(struct request_queue *q, char *page)
{
        return queue_var_show(blk_queue_dax(q), page);
}

static struct queue_sysfs_entry queue_requests_entry = {
        .attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
        .show = queue_requests_show,
        .store = queue_requests_store,
};

static struct queue_sysfs_entry queue_ra_entry = {
        .attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
        .show = queue_ra_show,
        .store = queue_ra_store,
};

static struct queue_sysfs_entry queue_max_sectors_entry = {
        .attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
        .show = queue_max_sectors_show,
        .store = queue_max_sectors_store,
};

static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
        .attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
        .show = queue_max_hw_sectors_show,
};

static struct queue_sysfs_entry queue_max_segments_entry = {
        .attr = {.name = "max_segments", .mode = S_IRUGO },
        .show = queue_max_segments_show,
};

static struct queue_sysfs_entry queue_max_discard_segments_entry = {
        .attr = {.name = "max_discard_segments", .mode = S_IRUGO },
        .show = queue_max_discard_segments_show,
};

static struct queue_sysfs_entry queue_max_integrity_segments_entry = {
        .attr = {.name = "max_integrity_segments", .mode = S_IRUGO },
        .show = queue_max_integrity_segments_show,
};

static struct queue_sysfs_entry queue_max_segment_size_entry = {
        .attr = {.name = "max_segment_size", .mode = S_IRUGO },
        .show = queue_max_segment_size_show,
};

static struct queue_sysfs_entry queue_iosched_entry = {
        .attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
        .show = elv_iosched_show,
        .store = elv_iosched_store,
};

static struct queue_sysfs_entry queue_hw_sector_size_entry = {
        .attr = {.name = "hw_sector_size", .mode = S_IRUGO },
        .show = queue_logical_block_size_show,
};

static struct queue_sysfs_entry queue_logical_block_size_entry = {
        .attr = {.name = "logical_block_size", .mode = S_IRUGO },
        .show = queue_logical_block_size_show,
};

static struct queue_sysfs_entry queue_physical_block_size_entry = {
        .attr = {.name = "physical_block_size", .mode = S_IRUGO },
        .show = queue_physical_block_size_show,
};

static struct queue_sysfs_entry queue_chunk_sectors_entry = {
        .attr = {.name = "chunk_sectors", .mode = S_IRUGO },
        .show = queue_chunk_sectors_show,
};

static struct queue_sysfs_entry queue_io_min_entry = {
        .attr = {.name = "minimum_io_size", .mode = S_IRUGO },
        .show = queue_io_min_show,
};

static struct queue_sysfs_entry queue_io_opt_entry = {
        .attr = {.name = "optimal_io_size", .mode = S_IRUGO },
        .show = queue_io_opt_show,
};

static struct queue_sysfs_entry queue_discard_granularity_entry = {
        .attr = {.name = "discard_granularity", .mode = S_IRUGO },
        .show = queue_discard_granularity_show,
};

static struct queue_sysfs_entry queue_discard_max_hw_entry = {
        .attr = {.name = "discard_max_hw_bytes", .mode = S_IRUGO },
        .show = queue_discard_max_hw_show,
};

static struct queue_sysfs_entry queue_discard_max_entry = {
        .attr = {.name = "discard_max_bytes", .mode = S_IRUGO | S_IWUSR },
        .show = queue_discard_max_show,
        .store = queue_discard_max_store,
};

static struct queue_sysfs_entry queue_discard_zeroes_data_entry = {
        .attr = {.name = "discard_zeroes_data", .mode = S_IRUGO },
        .show = queue_discard_zeroes_data_show,
};

static struct queue_sysfs_entry queue_write_same_max_entry = {
        .attr = {.name = "write_same_max_bytes", .mode = S_IRUGO },
        .show = queue_write_same_max_show,
};

static struct queue_sysfs_entry queue_write_zeroes_max_entry = {
        .attr = {.name = "write_zeroes_max_bytes", .mode = S_IRUGO },
        .show = queue_write_zeroes_max_show,
};

static struct queue_sysfs_entry queue_nonrot_entry = {
        .attr = {.name = "rotational", .mode = S_IRUGO | S_IWUSR },
        .show = queue_show_nonrot,
        .store = queue_store_nonrot,
};

static struct queue_sysfs_entry queue_zoned_entry = {
        .attr = {.name = "zoned", .mode = S_IRUGO },
        .show = queue_zoned_show,
};

static struct queue_sysfs_entry queue_nomerges_entry = {
        .attr = {.name = "nomerges", .mode = S_IRUGO | S_IWUSR },
        .show = queue_nomerges_show,
        .store = queue_nomerges_store,
};

static struct queue_sysfs_entry queue_rq_affinity_entry = {
        .attr = {.name = "rq_affinity", .mode = S_IRUGO | S_IWUSR },
        .show = queue_rq_affinity_show,
        .store = queue_rq_affinity_store,
};

static struct queue_sysfs_entry queue_iostats_entry = {
        .attr = {.name = "iostats", .mode = S_IRUGO | S_IWUSR },
        .show = queue_show_iostats,
        .store = queue_store_iostats,
};

static struct queue_sysfs_entry queue_random_entry = {
        .attr = {.name = "add_random", .mode = S_IRUGO | S_IWUSR },
        .show = queue_show_random,
        .store = queue_store_random,
};

static struct queue_sysfs_entry queue_poll_entry = {
        .attr = {.name = "io_poll", .mode = S_IRUGO | S_IWUSR },
        .show = queue_poll_show,
        .store = queue_poll_store,
};

static struct queue_sysfs_entry queue_poll_delay_entry = {
        .attr = {.name = "io_poll_delay", .mode = S_IRUGO | S_IWUSR },
        .show = queue_poll_delay_show,
        .store = queue_poll_delay_store,
};

static struct queue_sysfs_entry queue_wc_entry = {
        .attr = {.name = "write_cache", .mode = S_IRUGO | S_IWUSR },
        .show = queue_wc_show,
        .store = queue_wc_store,
};

static struct queue_sysfs_entry queue_dax_entry = {
        .attr = {.name = "dax", .mode = S_IRUGO },
        .show = queue_dax_show,
};

static struct queue_sysfs_entry queue_wb_lat_entry = {
        .attr = {.name = "wbt_lat_usec", .mode = S_IRUGO | S_IWUSR },
        .show = queue_wb_lat_show,
        .store = queue_wb_lat_store,
};

#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
static struct queue_sysfs_entry throtl_sample_time_entry = {
        .attr = {.name = "throttle_sample_time", .mode = S_IRUGO | S_IWUSR },
        .show = blk_throtl_sample_time_show,
        .store = blk_throtl_sample_time_store,
};
#endif

static struct attribute *default_attrs[] = {
        &queue_requests_entry.attr,
        &queue_ra_entry.attr,
        &queue_max_hw_sectors_entry.attr,
        &queue_max_sectors_entry.attr,
        &queue_max_segments_entry.attr,
        &queue_max_discard_segments_entry.attr,
        &queue_max_integrity_segments_entry.attr,
        &queue_max_segment_size_entry.attr,
        &queue_iosched_entry.attr,
        &queue_hw_sector_size_entry.attr,
        &queue_logical_block_size_entry.attr,
        &queue_physical_block_size_entry.attr,
        &queue_chunk_sectors_entry.attr,
        &queue_io_min_entry.attr,
        &queue_io_opt_entry.attr,
        &queue_discard_granularity_entry.attr,
        &queue_discard_max_entry.attr,
        &queue_discard_max_hw_entry.attr,
        &queue_discard_zeroes_data_entry.attr,
        &queue_write_same_max_entry.attr,
        &queue_write_zeroes_max_entry.attr,
        &queue_nonrot_entry.attr,
        &queue_zoned_entry.attr,
        &queue_nomerges_entry.attr,
        &queue_rq_affinity_entry.attr,
        &queue_iostats_entry.attr,
        &queue_random_entry.attr,
        &queue_poll_entry.attr,
        &queue_wc_entry.attr,
        &queue_dax_entry.attr,
        &queue_wb_lat_entry.attr,
        &queue_poll_delay_entry.attr,
#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
        &throtl_sample_time_entry.attr,
#endif
        NULL,
};

#define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)

static ssize_t
queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
{
        struct queue_sysfs_entry *entry = to_queue(attr);
        struct request_queue *q =
                container_of(kobj, struct request_queue, kobj);
        ssize_t res;

        if (!entry->show)
                return -EIO;
        mutex_lock(&q->sysfs_lock);
        if (blk_queue_dying(q)) {
                mutex_unlock(&q->sysfs_lock);
                return -ENOENT;
        }
        res = entry->show(q, page);
        mutex_unlock(&q->sysfs_lock);
        return res;
}

static ssize_t
queue_attr_store(struct kobject *kobj, struct attribute *attr,
                    const char *page, size_t length)
{
        struct queue_sysfs_entry *entry = to_queue(attr);
        struct request_queue *q;
        ssize_t res;

        if (!entry->store)
                return -EIO;

        q = container_of(kobj, struct request_queue, kobj);
        mutex_lock(&q->sysfs_lock);
        if (blk_queue_dying(q)) {
                mutex_unlock(&q->sysfs_lock);
                return -ENOENT;
        }
        res = entry->store(q, page, length);
        mutex_unlock(&q->sysfs_lock);
        return res;
}

static void blk_free_queue_rcu(struct rcu_head *rcu_head)
{
        struct request_queue *q = container_of(rcu_head, struct request_queue,
                                               rcu_head);
        kmem_cache_free(blk_requestq_cachep, q);
}

/**
 * __blk_release_queue - release a request queue when it is no longer needed
 * @work: pointer to the release_work member of the request queue to be released
 *
 * Description:
 *     blk_release_queue is the counterpart of blk_init_queue(). It should be
 *     called when a request queue is being released; typically when a block
 *     device is being de-registered. Its primary task it to free the queue
 *     itself.
 *
 * Notes:
 *     The low level driver must have finished any outstanding requests first
 *     via blk_cleanup_queue().
 *
 *     Although blk_release_queue() may be called with preemption disabled,
 *     __blk_release_queue() may sleep.
 */
static void __blk_release_queue(struct work_struct *work)
{
        struct request_queue *q = container_of(work, typeof(*q), release_work);

        if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags))
                blk_stat_remove_callback(q, q->poll_cb);
        blk_stat_free_callback(q->poll_cb);
        bdi_put(q->backing_dev_info);
        blkcg_exit_queue(q);

        if (q->elevator) {
                ioc_clear_queue(q);
                elevator_exit(q, q->elevator);
        }

        blk_free_queue_stats(q->stats);

        blk_exit_rl(q, &q->root_rl);

        if (q->queue_tags)
                __blk_queue_free_tags(q);

        if (!q->mq_ops) {
                if (q->exit_rq_fn)
                        q->exit_rq_fn(q, q->fq->flush_rq);
                blk_free_flush_queue(q->fq);
        } else {
                blk_mq_release(q);
        }

        blk_trace_shutdown(q);

        if (q->mq_ops)
                blk_mq_debugfs_unregister(q);

        if (q->bio_split)
                bioset_free(q->bio_split);

        ida_simple_remove(&blk_queue_ida, q->id);
        call_rcu(&q->rcu_head, blk_free_queue_rcu);
}

static void blk_release_queue(struct kobject *kobj)
{
        struct request_queue *q =
                container_of(kobj, struct request_queue, kobj);

        INIT_WORK(&q->release_work, __blk_release_queue);
        schedule_work(&q->release_work);
}

static const struct sysfs_ops queue_sysfs_ops = {
        .show   = queue_attr_show,
        .store  = queue_attr_store,
};

struct kobj_type blk_queue_ktype = {
        .sysfs_ops      = &queue_sysfs_ops,
        .default_attrs  = default_attrs,
        .release        = blk_release_queue,
};

int blk_register_queue(struct gendisk *disk)
{
        int ret;
        struct device *dev = disk_to_dev(disk);
        struct request_queue *q = disk->queue;

        if (WARN_ON(!q))
                return -ENXIO;

        WARN_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags),
                  "%s is registering an already registered queue\n",
                  kobject_name(&dev->kobj));
        queue_flag_set_unlocked(QUEUE_FLAG_REGISTERED, q);

        /*
         * SCSI probing may synchronously create and destroy a lot of
         * request_queues for non-existent devices.  Shutting down a fully
         * functional queue takes measureable wallclock time as RCU grace
         * periods are involved.  To avoid excessive latency in these
         * cases, a request_queue starts out in a degraded mode which is
         * faster to shut down and is made fully functional here as
         * request_queues for non-existent devices never get registered.
         */
        if (!blk_queue_init_done(q)) {
                queue_flag_set_unlocked(QUEUE_FLAG_INIT_DONE, q);
                percpu_ref_switch_to_percpu(&q->q_usage_counter);
                blk_queue_bypass_end(q);
        }

        ret = blk_trace_init_sysfs(dev);
        if (ret)
                return ret;

        /* Prevent changes through sysfs until registration is completed. */
        mutex_lock(&q->sysfs_lock);

        ret = kobject_add(&q->kobj, kobject_get(&dev->kobj), "%s", "queue");
        if (ret < 0) {
                blk_trace_remove_sysfs(dev);
                goto unlock;
        }

        if (q->mq_ops) {
                __blk_mq_register_dev(dev, q);
                blk_mq_debugfs_register(q);
        }

        kobject_uevent(&q->kobj, KOBJ_ADD);

        wbt_enable_default(q);

        blk_throtl_register_queue(q);

        if (q->request_fn || (q->mq_ops && q->elevator)) {
                ret = elv_register_queue(q);
                if (ret) {
                        kobject_uevent(&q->kobj, KOBJ_REMOVE);
                        kobject_del(&q->kobj);
                        blk_trace_remove_sysfs(dev);
                        kobject_put(&dev->kobj);
                        goto unlock;
                }
        }
        ret = 0;
unlock:
        mutex_unlock(&q->sysfs_lock);
        return ret;
}

void blk_unregister_queue(struct gendisk *disk)
{
        struct request_queue *q = disk->queue;

        if (WARN_ON(!q))
                return;

        queue_flag_clear_unlocked(QUEUE_FLAG_REGISTERED, q);

        wbt_exit(q);


        if (q->mq_ops)
                blk_mq_unregister_dev(disk_to_dev(disk), q);

        if (q->request_fn || (q->mq_ops && q->elevator))
                elv_unregister_queue(q);

        kobject_uevent(&q->kobj, KOBJ_REMOVE);
        kobject_del(&q->kobj);
        blk_trace_remove_sysfs(disk_to_dev(disk));
        kobject_put(&disk_to_dev(disk)->kobj);
}