/*
 * Copyright (C) 2012 Red Hat, Inc.
 *
 * This file is released under the GPL.
 */

#include "dm.h"
#include "dm-bio-prison.h"

#include <linux/spinlock.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/slab.h>

/*----------------------------------------------------------------*/

#define MIN_CELLS 1024

struct dm_bio_prison {
        spinlock_t lock;
        mempool_t *cell_pool;
        struct rb_root cells;
};

static struct kmem_cache *_cell_cache;

/*----------------------------------------------------------------*/

/*
 * @nr_cells should be the number of cells you want in use _concurrently_.
 * Don't confuse it with the number of distinct keys.
 */
struct dm_bio_prison *dm_bio_prison_create(void)
{
        struct dm_bio_prison *prison = kmalloc(sizeof(*prison), GFP_KERNEL);

        if (!prison)
                return NULL;

        spin_lock_init(&prison->lock);

        prison->cell_pool = mempool_create_slab_pool(MIN_CELLS, _cell_cache);
        if (!prison->cell_pool) {
                kfree(prison);
                return NULL;
        }

        prison->cells = RB_ROOT;

        return prison;
}
EXPORT_SYMBOL_GPL(dm_bio_prison_create);

void dm_bio_prison_destroy(struct dm_bio_prison *prison)
{
        mempool_destroy(prison->cell_pool);
        kfree(prison);
}
EXPORT_SYMBOL_GPL(dm_bio_prison_destroy);

struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison, gfp_t gfp)
{
        return mempool_alloc(prison->cell_pool, gfp);
}
EXPORT_SYMBOL_GPL(dm_bio_prison_alloc_cell);

void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
                             struct dm_bio_prison_cell *cell)
{
        mempool_free(cell, prison->cell_pool);
}
EXPORT_SYMBOL_GPL(dm_bio_prison_free_cell);

static void __setup_new_cell(struct dm_cell_key *key,
                             struct bio *holder,
                             struct dm_bio_prison_cell *cell)
{
       memcpy(&cell->key, key, sizeof(cell->key));
       cell->holder = holder;
       bio_list_init(&cell->bios);
}

static int cmp_keys(struct dm_cell_key *lhs,
                    struct dm_cell_key *rhs)
{
        if (lhs->virtual < rhs->virtual)
                return -1;

        if (lhs->virtual > rhs->virtual)
                return 1;

        if (lhs->dev < rhs->dev)
                return -1;

        if (lhs->dev > rhs->dev)
                return 1;

        if (lhs->block_end <= rhs->block_begin)
                return -1;

        if (lhs->block_begin >= rhs->block_end)
                return 1;

        return 0;
}

static int __bio_detain(struct dm_bio_prison *prison,
                        struct dm_cell_key *key,
                        struct bio *inmate,
                        struct dm_bio_prison_cell *cell_prealloc,
                        struct dm_bio_prison_cell **cell_result)
{
        int r;
        struct rb_node **new = &prison->cells.rb_node, *parent = NULL;

        while (*new) {
                struct dm_bio_prison_cell *cell =
                        container_of(*new, struct dm_bio_prison_cell, node);

                r = cmp_keys(key, &cell->key);

                parent = *new;
                if (r < 0)
                        new = &((*new)->rb_left);
                else if (r > 0)
                        new = &((*new)->rb_right);
                else {
                        if (inmate)
                                bio_list_add(&cell->bios, inmate);
                        *cell_result = cell;
                        return 1;
                }
        }

        __setup_new_cell(key, inmate, cell_prealloc);
        *cell_result = cell_prealloc;

        rb_link_node(&cell_prealloc->node, parent, new);
        rb_insert_color(&cell_prealloc->node, &prison->cells);

        return 0;
}

static int bio_detain(struct dm_bio_prison *prison,
                      struct dm_cell_key *key,
                      struct bio *inmate,
                      struct dm_bio_prison_cell *cell_prealloc,
                      struct dm_bio_prison_cell **cell_result)
{
        int r;
        unsigned long flags;

        spin_lock_irqsave(&prison->lock, flags);
        r = __bio_detain(prison, key, inmate, cell_prealloc, cell_result);
        spin_unlock_irqrestore(&prison->lock, flags);

        return r;
}

int dm_bio_detain(struct dm_bio_prison *prison,
                  struct dm_cell_key *key,
                  struct bio *inmate,
                  struct dm_bio_prison_cell *cell_prealloc,
                  struct dm_bio_prison_cell **cell_result)
{
        return bio_detain(prison, key, inmate, cell_prealloc, cell_result);
}
EXPORT_SYMBOL_GPL(dm_bio_detain);

int dm_get_cell(struct dm_bio_prison *prison,
                struct dm_cell_key *key,
                struct dm_bio_prison_cell *cell_prealloc,
                struct dm_bio_prison_cell **cell_result)
{
        return bio_detain(prison, key, NULL, cell_prealloc, cell_result);
}
EXPORT_SYMBOL_GPL(dm_get_cell);

/*
 * @inmates must have been initialised prior to this call
 */
static void __cell_release(struct dm_bio_prison *prison,
                           struct dm_bio_prison_cell *cell,
                           struct bio_list *inmates)
{
        rb_erase(&cell->node, &prison->cells);

        if (inmates) {
                if (cell->holder)
                        bio_list_add(inmates, cell->holder);
                bio_list_merge(inmates, &cell->bios);
        }
}

void dm_cell_release(struct dm_bio_prison *prison,
                     struct dm_bio_prison_cell *cell,
                     struct bio_list *bios)
{
        unsigned long flags;

        spin_lock_irqsave(&prison->lock, flags);
        __cell_release(prison, cell, bios);
        spin_unlock_irqrestore(&prison->lock, flags);
}
EXPORT_SYMBOL_GPL(dm_cell_release);

/*
 * Sometimes we don't want the holder, just the additional bios.
 */
static void __cell_release_no_holder(struct dm_bio_prison *prison,
                                     struct dm_bio_prison_cell *cell,
                                     struct bio_list *inmates)
{
        rb_erase(&cell->node, &prison->cells);
        bio_list_merge(inmates, &cell->bios);
}

void dm_cell_release_no_holder(struct dm_bio_prison *prison,
                               struct dm_bio_prison_cell *cell,
                               struct bio_list *inmates)
{
        unsigned long flags;

        spin_lock_irqsave(&prison->lock, flags);
        __cell_release_no_holder(prison, cell, inmates);
        spin_unlock_irqrestore(&prison->lock, flags);
}
EXPORT_SYMBOL_GPL(dm_cell_release_no_holder);

void dm_cell_error(struct dm_bio_prison *prison,
                   struct dm_bio_prison_cell *cell, int error)
{
        struct bio_list bios;
        struct bio *bio;

        bio_list_init(&bios);
        dm_cell_release(prison, cell, &bios);

        while ((bio = bio_list_pop(&bios))) {
                bio->bi_error = error;
                bio_endio(bio);
        }
}
EXPORT_SYMBOL_GPL(dm_cell_error);

void dm_cell_visit_release(struct dm_bio_prison *prison,
                           void (*visit_fn)(void *, struct dm_bio_prison_cell *),
                           void *context,
                           struct dm_bio_prison_cell *cell)
{
        unsigned long flags;

        spin_lock_irqsave(&prison->lock, flags);
        visit_fn(context, cell);
        rb_erase(&cell->node, &prison->cells);
        spin_unlock_irqrestore(&prison->lock, flags);
}
EXPORT_SYMBOL_GPL(dm_cell_visit_release);

static int __promote_or_release(struct dm_bio_prison *prison,
                                struct dm_bio_prison_cell *cell)
{
        if (bio_list_empty(&cell->bios)) {
                rb_erase(&cell->node, &prison->cells);
                return 1;
        }

        cell->holder = bio_list_pop(&cell->bios);
        return 0;
}

int dm_cell_promote_or_release(struct dm_bio_prison *prison,
                               struct dm_bio_prison_cell *cell)
{
        int r;
        unsigned long flags;

        spin_lock_irqsave(&prison->lock, flags);
        r = __promote_or_release(prison, cell);
        spin_unlock_irqrestore(&prison->lock, flags);

        return r;
}
EXPORT_SYMBOL_GPL(dm_cell_promote_or_release);

/*----------------------------------------------------------------*/

#define DEFERRED_SET_SIZE 64

struct dm_deferred_entry {
        struct dm_deferred_set *ds;
        unsigned count;
        struct list_head work_items;
};

struct dm_deferred_set {
        spinlock_t lock;
        unsigned current_entry;
        unsigned sweeper;
        struct dm_deferred_entry entries[DEFERRED_SET_SIZE];
};

struct dm_deferred_set *dm_deferred_set_create(void)
{
        int i;
        struct dm_deferred_set *ds;

        ds = kmalloc(sizeof(*ds), GFP_KERNEL);
        if (!ds)
                return NULL;

        spin_lock_init(&ds->lock);
        ds->current_entry = 0;
        ds->sweeper = 0;
        for (i = 0; i < DEFERRED_SET_SIZE; i++) {
                ds->entries[i].ds = ds;
                ds->entries[i].count = 0;
                INIT_LIST_HEAD(&ds->entries[i].work_items);
        }

        return ds;
}
EXPORT_SYMBOL_GPL(dm_deferred_set_create);

void dm_deferred_set_destroy(struct dm_deferred_set *ds)
{
        kfree(ds);
}
EXPORT_SYMBOL_GPL(dm_deferred_set_destroy);

struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds)
{
        unsigned long flags;
        struct dm_deferred_entry *entry;

        spin_lock_irqsave(&ds->lock, flags);
        entry = ds->entries + ds->current_entry;
        entry->count++;
        spin_unlock_irqrestore(&ds->lock, flags);

        return entry;
}
EXPORT_SYMBOL_GPL(dm_deferred_entry_inc);

static unsigned ds_next(unsigned index)
{
        return (index + 1) % DEFERRED_SET_SIZE;
}

static void __sweep(struct dm_deferred_set *ds, struct list_head *head)
{
        while ((ds->sweeper != ds->current_entry) &&
               !ds->entries[ds->sweeper].count) {
                list_splice_init(&ds->entries[ds->sweeper].work_items, head);
                ds->sweeper = ds_next(ds->sweeper);
        }

        if ((ds->sweeper == ds->current_entry) && !ds->entries[ds->sweeper].count)
                list_splice_init(&ds->entries[ds->sweeper].work_items, head);
}

void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head)
{
        unsigned long flags;

        spin_lock_irqsave(&entry->ds->lock, flags);
        BUG_ON(!entry->count);
        --entry->count;
        __sweep(entry->ds, head);
        spin_unlock_irqrestore(&entry->ds->lock, flags);
}
EXPORT_SYMBOL_GPL(dm_deferred_entry_dec);

/*
 * Returns 1 if deferred or 0 if no pending items to delay job.
 */
int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work)
{
        int r = 1;
        unsigned long flags;
        unsigned next_entry;

        spin_lock_irqsave(&ds->lock, flags);
        if ((ds->sweeper == ds->current_entry) &&
            !ds->entries[ds->current_entry].count)
                r = 0;
        else {
                list_add(work, &ds->entries[ds->current_entry].work_items);
                next_entry = ds_next(ds->current_entry);
                if (!ds->entries[next_entry].count)
                        ds->current_entry = next_entry;
        }
        spin_unlock_irqrestore(&ds->lock, flags);

        return r;
}
EXPORT_SYMBOL_GPL(dm_deferred_set_add_work);

/*----------------------------------------------------------------*/

static int __init dm_bio_prison_init(void)
{
        _cell_cache = KMEM_CACHE(dm_bio_prison_cell, 0);
        if (!_cell_cache)
                return -ENOMEM;

        return 0;
}

static void __exit dm_bio_prison_exit(void)
{
        kmem_cache_destroy(_cell_cache);
        _cell_cache = NULL;
}

/*
 * module hooks
 */
module_init(dm_bio_prison_init);
module_exit(dm_bio_prison_exit);

MODULE_DESCRIPTION(DM_NAME " bio prison");
MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");