/*
 * Functions related to sysfs handling
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/blktrace_api.h>

#include "blk.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 int var, char *page)
{
        return sprintf(page, "%d\n", var);
}

static ssize_t
queue_var_store(unsigned long *var, const char *page, size_t count)
{
        char *p = (char *) page;

        *var = simple_strtoul(p, &p, 10);
        return count;
}

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)
{
        struct request_list *rl = &q->rq;
        unsigned long nr;
        int ret = queue_var_store(&nr, page, count);
        if (nr < BLKDEV_MIN_RQ)
                nr = BLKDEV_MIN_RQ;

        spin_lock_irq(q->queue_lock);
        q->nr_requests = nr;
        blk_queue_congestion_threshold(q);

        if (rl->count[READ] >= queue_congestion_on_threshold(q))
                blk_set_queue_congested(q, READ);
        else if (rl->count[READ] < queue_congestion_off_threshold(q))
                blk_clear_queue_congested(q, READ);

        if (rl->count[WRITE] >= queue_congestion_on_threshold(q))
                blk_set_queue_congested(q, WRITE);
        else if (rl->count[WRITE] < queue_congestion_off_threshold(q))
                blk_clear_queue_congested(q, WRITE);

        if (rl->count[READ] >= q->nr_requests) {
                blk_set_queue_full(q, READ);
        } else if (rl->count[READ]+1 <= q->nr_requests) {
                blk_clear_queue_full(q, READ);
                wake_up(&rl->wait[READ]);
        }

        if (rl->count[WRITE] >= q->nr_requests) {
                blk_set_queue_full(q, WRITE);
        } else if (rl->count[WRITE]+1 <= q->nr_requests) {
                blk_clear_queue_full(q, WRITE);
                wake_up(&rl->wait[WRITE]);
        }
        spin_unlock_irq(q->queue_lock);
        return ret;
}

static ssize_t queue_ra_show(struct request_queue *q, char *page)
{
        int ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_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);

        spin_lock_irq(q->queue_lock);
        q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
        spin_unlock_irq(q->queue_lock);

        return ret;
}

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

        return queue_var_show(max_sectors_kb, (page));
}

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

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 = q->max_hw_sectors >> 1,
                        page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
        ssize_t ret = queue_var_store(&max_sectors_kb, page, count);

        if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
                return -EINVAL;
        /*
         * Take the queue lock to update the readahead and max_sectors
         * values synchronously:
         */
        spin_lock_irq(q->queue_lock);
        q->max_sectors = max_sectors_kb << 1;
        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 = q->max_hw_sectors >> 1;

        return queue_var_show(max_hw_sectors_kb, (page));
}

static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
{
        return queue_var_show(blk_queue_nomerges(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);

        spin_lock_irq(q->queue_lock);
        if (nm)
                queue_flag_set(QUEUE_FLAG_NOMERGES, q);
        else
                queue_flag_clear(QUEUE_FLAG_NOMERGES, q);

        spin_unlock_irq(q->queue_lock);
        return ret;
}


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_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_hw_sector_size_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 attribute *default_attrs[] = {
        &queue_requests_entry.attr,
        &queue_ra_entry.attr,
        &queue_max_hw_sectors_entry.attr,
        &queue_max_sectors_entry.attr,
        &queue_iosched_entry.attr,
        &queue_hw_sector_size_entry.attr,
        &queue_nomerges_entry.attr,
        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 (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
                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 (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
                mutex_unlock(&q->sysfs_lock);
                return -ENOENT;
        }
        res = entry->store(q, page, length);
        mutex_unlock(&q->sysfs_lock);
        return res;
}

/**
 * blk_cleanup_queue: - release a &struct request_queue when it is no longer needed
 * @kobj:    the kobj belonging of the request queue to be released
 *
 * Description:
 *     blk_cleanup_queue is the pair to blk_init_queue() or
 *     blk_queue_make_request().  It should be called when a request queue is
 *     being released; typically when a block device is being de-registered.
 *     Currently, its primary task it to free all the &struct request
 *     structures that were allocated to the queue and the queue itself.
 *
 * Caveat:
 *     Hopefully the low level driver will have finished any
 *     outstanding requests first...
 **/
static void blk_release_queue(struct kobject *kobj)
{
        struct request_queue *q =
                container_of(kobj, struct request_queue, kobj);
        struct request_list *rl = &q->rq;

        blk_sync_queue(q);

        if (rl->rq_pool)
                mempool_destroy(rl->rq_pool);

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

        blk_trace_shutdown(q);

        bdi_destroy(&q->backing_dev_info);
        kmem_cache_free(blk_requestq_cachep, q);
}

static 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 request_queue *q = disk->queue;

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

        if (!q->request_fn)
                return 0;

        ret = kobject_add(&q->kobj, kobject_get(&disk->dev.kobj),
                          "%s", "queue");
        if (ret < 0)
                return ret;

        kobject_uevent(&q->kobj, KOBJ_ADD);

        ret = elv_register_queue(q);
        if (ret) {
                kobject_uevent(&q->kobj, KOBJ_REMOVE);
                kobject_del(&q->kobj);
                return ret;
        }

        return 0;
}

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

        if (WARN_ON(!q))
                return;

        if (q->request_fn) {
                elv_unregister_queue(q);

                kobject_uevent(&q->kobj, KOBJ_REMOVE);
                kobject_del(&q->kobj);
                kobject_put(&disk->dev.kobj);
        }
}