/*
 * Copyright (C) 2011 Red Hat, Inc.
 *
 * This file is released under the GPL.
 */
#include "dm-transaction-manager.h"
#include "dm-space-map.h"
#include "dm-space-map-disk.h"
#include "dm-space-map-metadata.h"
#include "dm-persistent-data-internal.h"

#include <linux/export.h>
#include <linux/mutex.h>
#include <linux/hash.h>
#include <linux/slab.h>
#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "transaction manager"

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

#define PREFETCH_SIZE 128
#define PREFETCH_BITS 7
#define PREFETCH_SENTINEL ((dm_block_t) -1ULL)

struct prefetch_set {
        struct mutex lock;
        dm_block_t blocks[PREFETCH_SIZE];
};

static unsigned prefetch_hash(dm_block_t b)
{
        return hash_64(b, PREFETCH_BITS);
}

static void prefetch_wipe(struct prefetch_set *p)
{
        unsigned i;
        for (i = 0; i < PREFETCH_SIZE; i++)
                p->blocks[i] = PREFETCH_SENTINEL;
}

static void prefetch_init(struct prefetch_set *p)
{
        mutex_init(&p->lock);
        prefetch_wipe(p);
}

static void prefetch_add(struct prefetch_set *p, dm_block_t b)
{
        unsigned h = prefetch_hash(b);

        mutex_lock(&p->lock);
        if (p->blocks[h] == PREFETCH_SENTINEL)
                p->blocks[h] = b;

        mutex_unlock(&p->lock);
}

static void prefetch_issue(struct prefetch_set *p, struct dm_block_manager *bm)
{
        unsigned i;

        mutex_lock(&p->lock);

        for (i = 0; i < PREFETCH_SIZE; i++)
                if (p->blocks[i] != PREFETCH_SENTINEL) {
                        dm_bm_prefetch(bm, p->blocks[i]);
                        p->blocks[i] = PREFETCH_SENTINEL;
                }

        mutex_unlock(&p->lock);
}

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

struct shadow_info {
        struct hlist_node hlist;
        dm_block_t where;
};

/*
 * It would be nice if we scaled with the size of transaction.
 */
#define DM_HASH_SIZE 256
#define DM_HASH_MASK (DM_HASH_SIZE - 1)

struct dm_transaction_manager {
        int is_clone;
        struct dm_transaction_manager *real;

        struct dm_block_manager *bm;
        struct dm_space_map *sm;

        spinlock_t lock;
        struct hlist_head buckets[DM_HASH_SIZE];

        struct prefetch_set prefetches;
};

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

static int is_shadow(struct dm_transaction_manager *tm, dm_block_t b)
{
        int r = 0;
        unsigned bucket = dm_hash_block(b, DM_HASH_MASK);
        struct shadow_info *si;

        spin_lock(&tm->lock);
        hlist_for_each_entry(si, tm->buckets + bucket, hlist)
                if (si->where == b) {
                        r = 1;
                        break;
                }
        spin_unlock(&tm->lock);

        return r;
}

/*
 * This can silently fail if there's no memory.  We're ok with this since
 * creating redundant shadows causes no harm.
 */
static void insert_shadow(struct dm_transaction_manager *tm, dm_block_t b)
{
        unsigned bucket;
        struct shadow_info *si;

        si = kmalloc(sizeof(*si), GFP_NOIO);
        if (si) {
                si->where = b;
                bucket = dm_hash_block(b, DM_HASH_MASK);
                spin_lock(&tm->lock);
                hlist_add_head(&si->hlist, tm->buckets + bucket);
                spin_unlock(&tm->lock);
        }
}

static void wipe_shadow_table(struct dm_transaction_manager *tm)
{
        struct shadow_info *si;
        struct hlist_node *tmp;
        struct hlist_head *bucket;
        int i;

        spin_lock(&tm->lock);
        for (i = 0; i < DM_HASH_SIZE; i++) {
                bucket = tm->buckets + i;
                hlist_for_each_entry_safe(si, tmp, bucket, hlist)
                        kfree(si);

                INIT_HLIST_HEAD(bucket);
        }

        spin_unlock(&tm->lock);
}

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

static struct dm_transaction_manager *dm_tm_create(struct dm_block_manager *bm,
                                                   struct dm_space_map *sm)
{
        int i;
        struct dm_transaction_manager *tm;

        tm = kmalloc(sizeof(*tm), GFP_KERNEL);
        if (!tm)
                return ERR_PTR(-ENOMEM);

        tm->is_clone = 0;
        tm->real = NULL;
        tm->bm = bm;
        tm->sm = sm;

        spin_lock_init(&tm->lock);
        for (i = 0; i < DM_HASH_SIZE; i++)
                INIT_HLIST_HEAD(tm->buckets + i);

        prefetch_init(&tm->prefetches);

        return tm;
}

struct dm_transaction_manager *dm_tm_create_non_blocking_clone(struct dm_transaction_manager *real)
{
        struct dm_transaction_manager *tm;

        tm = kmalloc(sizeof(*tm), GFP_KERNEL);
        if (tm) {
                tm->is_clone = 1;
                tm->real = real;
        }

        return tm;
}
EXPORT_SYMBOL_GPL(dm_tm_create_non_blocking_clone);

void dm_tm_destroy(struct dm_transaction_manager *tm)
{
        if (!tm->is_clone)
                wipe_shadow_table(tm);

        kfree(tm);
}
EXPORT_SYMBOL_GPL(dm_tm_destroy);

int dm_tm_pre_commit(struct dm_transaction_manager *tm)
{
        int r;

        if (tm->is_clone)
                return -EWOULDBLOCK;

        r = dm_sm_commit(tm->sm);
        if (r < 0)
                return r;

        return dm_bm_flush(tm->bm);
}
EXPORT_SYMBOL_GPL(dm_tm_pre_commit);

int dm_tm_commit(struct dm_transaction_manager *tm, struct dm_block *root)
{
        if (tm->is_clone)
                return -EWOULDBLOCK;

        wipe_shadow_table(tm);
        dm_bm_unlock(root);

        return dm_bm_flush(tm->bm);
}
EXPORT_SYMBOL_GPL(dm_tm_commit);

int dm_tm_new_block(struct dm_transaction_manager *tm,
                    struct dm_block_validator *v,
                    struct dm_block **result)
{
        int r;
        dm_block_t new_block;

        if (tm->is_clone)
                return -EWOULDBLOCK;

        r = dm_sm_new_block(tm->sm, &new_block);
        if (r < 0)
                return r;

        r = dm_bm_write_lock_zero(tm->bm, new_block, v, result);
        if (r < 0) {
                dm_sm_dec_block(tm->sm, new_block);
                return r;
        }

        /*
         * New blocks count as shadows in that they don't need to be
         * shadowed again.
         */
        insert_shadow(tm, new_block);

        return 0;
}

static int __shadow_block(struct dm_transaction_manager *tm, dm_block_t orig,
                          struct dm_block_validator *v,
                          struct dm_block **result)
{
        int r;
        dm_block_t new;
        struct dm_block *orig_block;

        r = dm_sm_new_block(tm->sm, &new);
        if (r < 0)
                return r;

        r = dm_sm_dec_block(tm->sm, orig);
        if (r < 0)
                return r;

        r = dm_bm_read_lock(tm->bm, orig, v, &orig_block);
        if (r < 0)
                return r;

        /*
         * It would be tempting to use dm_bm_unlock_move here, but some
         * code, such as the space maps, keeps using the old data structures
         * secure in the knowledge they won't be changed until the next
         * transaction.  Using unlock_move would force a synchronous read
         * since the old block would no longer be in the cache.
         */
        r = dm_bm_write_lock_zero(tm->bm, new, v, result);
        if (r) {
                dm_bm_unlock(orig_block);
                return r;
        }

        memcpy(dm_block_data(*result), dm_block_data(orig_block),
               dm_bm_block_size(tm->bm));

        dm_bm_unlock(orig_block);
        return r;
}

int dm_tm_shadow_block(struct dm_transaction_manager *tm, dm_block_t orig,
                       struct dm_block_validator *v, struct dm_block **result,
                       int *inc_children)
{
        int r;

        if (tm->is_clone)
                return -EWOULDBLOCK;

        r = dm_sm_count_is_more_than_one(tm->sm, orig, inc_children);
        if (r < 0)
                return r;

        if (is_shadow(tm, orig) && !*inc_children)
                return dm_bm_write_lock(tm->bm, orig, v, result);

        r = __shadow_block(tm, orig, v, result);
        if (r < 0)
                return r;
        insert_shadow(tm, dm_block_location(*result));

        return r;
}
EXPORT_SYMBOL_GPL(dm_tm_shadow_block);

int dm_tm_read_lock(struct dm_transaction_manager *tm, dm_block_t b,
                    struct dm_block_validator *v,
                    struct dm_block **blk)
{
        if (tm->is_clone) {
                int r = dm_bm_read_try_lock(tm->real->bm, b, v, blk);

                if (r == -EWOULDBLOCK)
                        prefetch_add(&tm->real->prefetches, b);

                return r;
        }

        return dm_bm_read_lock(tm->bm, b, v, blk);
}
EXPORT_SYMBOL_GPL(dm_tm_read_lock);

void dm_tm_unlock(struct dm_transaction_manager *tm, struct dm_block *b)
{
        dm_bm_unlock(b);
}
EXPORT_SYMBOL_GPL(dm_tm_unlock);

void dm_tm_inc(struct dm_transaction_manager *tm, dm_block_t b)
{
        /*
         * The non-blocking clone doesn't support this.
         */
        BUG_ON(tm->is_clone);

        dm_sm_inc_block(tm->sm, b);
}
EXPORT_SYMBOL_GPL(dm_tm_inc);

void dm_tm_dec(struct dm_transaction_manager *tm, dm_block_t b)
{
        /*
         * The non-blocking clone doesn't support this.
         */
        BUG_ON(tm->is_clone);

        dm_sm_dec_block(tm->sm, b);
}
EXPORT_SYMBOL_GPL(dm_tm_dec);

int dm_tm_ref(struct dm_transaction_manager *tm, dm_block_t b,
              uint32_t *result)
{
        if (tm->is_clone)
                return -EWOULDBLOCK;

        return dm_sm_get_count(tm->sm, b, result);
}

struct dm_block_manager *dm_tm_get_bm(struct dm_transaction_manager *tm)
{
        return tm->bm;
}

void dm_tm_issue_prefetches(struct dm_transaction_manager *tm)
{
        prefetch_issue(&tm->prefetches, tm->bm);
}
EXPORT_SYMBOL_GPL(dm_tm_issue_prefetches);

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

static int dm_tm_create_internal(struct dm_block_manager *bm,
                                 dm_block_t sb_location,
                                 struct dm_transaction_manager **tm,
                                 struct dm_space_map **sm,
                                 int create,
                                 void *sm_root, size_t sm_len)
{
        int r;

        *sm = dm_sm_metadata_init();
        if (IS_ERR(*sm))
                return PTR_ERR(*sm);

        *tm = dm_tm_create(bm, *sm);
        if (IS_ERR(*tm)) {
                dm_sm_destroy(*sm);
                return PTR_ERR(*tm);
        }

        if (create) {
                r = dm_sm_metadata_create(*sm, *tm, dm_bm_nr_blocks(bm),
                                          sb_location);
                if (r) {
                        DMERR("couldn't create metadata space map");
                        goto bad;
                }

        } else {
                r = dm_sm_metadata_open(*sm, *tm, sm_root, sm_len);
                if (r) {
                        DMERR("couldn't open metadata space map");
                        goto bad;
                }
        }

        return 0;

bad:
        dm_tm_destroy(*tm);
        dm_sm_destroy(*sm);
        return r;
}

int dm_tm_create_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
                         struct dm_transaction_manager **tm,
                         struct dm_space_map **sm)
{
        return dm_tm_create_internal(bm, sb_location, tm, sm, 1, NULL, 0);
}
EXPORT_SYMBOL_GPL(dm_tm_create_with_sm);

int dm_tm_open_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
                       void *sm_root, size_t root_len,
                       struct dm_transaction_manager **tm,
                       struct dm_space_map **sm)
{
        return dm_tm_create_internal(bm, sb_location, tm, sm, 0, sm_root, root_len);
}
EXPORT_SYMBOL_GPL(dm_tm_open_with_sm);

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