/*
 * Copyright (C) 2015 IT University of Copenhagen
 * Initial release: Matias Bjorling <m@bjorling.me>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * Implementation of a Round-robin page-based Hybrid FTL for Open-channel SSDs.
 */

#ifndef RRPC_H_
#define RRPC_H_

#include <linux/blkdev.h>
#include <linux/blk-mq.h>
#include <linux/bio.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/vmalloc.h>

#include <linux/lightnvm.h>

/* Run only GC if less than 1/X blocks are free */
#define GC_LIMIT_INVERSE 10
#define GC_TIME_SECS 100

#define RRPC_SECTOR (512)
#define RRPC_EXPOSED_PAGE_SIZE (4096)

#define NR_PHY_IN_LOG (RRPC_EXPOSED_PAGE_SIZE / RRPC_SECTOR)

struct rrpc_inflight {
        struct list_head reqs;
        spinlock_t lock;
};

struct rrpc_inflight_rq {
        struct list_head list;
        sector_t l_start;
        sector_t l_end;
};

struct rrpc_rq {
        struct rrpc_inflight_rq inflight_rq;
        struct rrpc_addr *addr;
        unsigned long flags;
};

struct rrpc_block {
        struct nvm_block *parent;
        struct rrpc_lun *rlun;
        struct list_head prio;
        struct list_head list;

#define MAX_INVALID_PAGES_STORAGE 8
        /* Bitmap for invalid page intries */
        unsigned long invalid_pages[MAX_INVALID_PAGES_STORAGE];
        /* points to the next writable page within a block */
        unsigned int next_page;
        /* number of pages that are invalid, wrt host page size */
        unsigned int nr_invalid_pages;

        spinlock_t lock;
        atomic_t data_cmnt_size; /* data pages committed to stable storage */
};

struct rrpc_lun {
        struct rrpc *rrpc;
        struct nvm_lun *parent;
        struct rrpc_block *cur, *gc_cur;
        struct rrpc_block *blocks;      /* Reference to block allocation */

        struct list_head prio_list;     /* Blocks that may be GC'ed */
        struct list_head open_list;     /* In-use open blocks. These are blocks
                                         * that can be both written to and read
                                         * from
                                         */
        struct list_head closed_list;   /* In-use closed blocks. These are
                                         * blocks that can _only_ be read from
                                         */

        struct work_struct ws_gc;

        spinlock_t lock;
};

struct rrpc {
        /* instance must be kept in top to resolve rrpc in unprep */
        struct nvm_tgt_instance instance;

        struct nvm_dev *dev;
        struct gendisk *disk;

        sector_t soffset; /* logical sector offset */
        u64 poffset; /* physical page offset */
        int lun_offset;

        int nr_luns;
        struct rrpc_lun *luns;

        /* calculated values */
        unsigned long long nr_sects;
        unsigned long total_blocks;

        /* Write strategy variables. Move these into each for structure for each
         * strategy
         */
        atomic_t next_lun; /* Whenever a page is written, this is updated
                            * to point to the next write lun
                            */

        spinlock_t bio_lock;
        struct bio_list requeue_bios;
        struct work_struct ws_requeue;

        /* Simple translation map of logical addresses to physical addresses.
         * The logical addresses is known by the host system, while the physical
         * addresses are used when writing to the disk block device.
         */
        struct rrpc_addr *trans_map;
        /* also store a reverse map for garbage collection */
        struct rrpc_rev_addr *rev_trans_map;
        spinlock_t rev_lock;

        struct rrpc_inflight inflights;

        mempool_t *addr_pool;
        mempool_t *page_pool;
        mempool_t *gcb_pool;
        mempool_t *rq_pool;

        struct timer_list gc_timer;
        struct workqueue_struct *krqd_wq;
        struct workqueue_struct *kgc_wq;
};

struct rrpc_block_gc {
        struct rrpc *rrpc;
        struct rrpc_block *rblk;
        struct work_struct ws_gc;
};

/* Logical to physical mapping */
struct rrpc_addr {
        u64 addr;
        struct rrpc_block *rblk;
};

/* Physical to logical mapping */
struct rrpc_rev_addr {
        u64 addr;
};

static inline struct rrpc_block *rrpc_get_rblk(struct rrpc_lun *rlun,
                                                                int blk_id)
{
        struct rrpc *rrpc = rlun->rrpc;
        int lun_blk = blk_id % rrpc->dev->blks_per_lun;

        return &rlun->blocks[lun_blk];
}

static inline sector_t rrpc_get_laddr(struct bio *bio)
{
        return bio->bi_iter.bi_sector / NR_PHY_IN_LOG;
}

static inline unsigned int rrpc_get_pages(struct bio *bio)
{
        return  bio->bi_iter.bi_size / RRPC_EXPOSED_PAGE_SIZE;
}

static inline sector_t rrpc_get_sector(sector_t laddr)
{
        return laddr * NR_PHY_IN_LOG;
}

static inline int request_intersects(struct rrpc_inflight_rq *r,
                                sector_t laddr_start, sector_t laddr_end)
{
        return (laddr_end >= r->l_start) && (laddr_start <= r->l_end);
}

static int __rrpc_lock_laddr(struct rrpc *rrpc, sector_t laddr,
                             unsigned pages, struct rrpc_inflight_rq *r)
{
        sector_t laddr_end = laddr + pages - 1;
        struct rrpc_inflight_rq *rtmp;

        WARN_ON(irqs_disabled());

        spin_lock_irq(&rrpc->inflights.lock);
        list_for_each_entry(rtmp, &rrpc->inflights.reqs, list) {
                if (unlikely(request_intersects(rtmp, laddr, laddr_end))) {
                        /* existing, overlapping request, come back later */
                        spin_unlock_irq(&rrpc->inflights.lock);
                        return 1;
                }
        }

        r->l_start = laddr;
        r->l_end = laddr_end;

        list_add_tail(&r->list, &rrpc->inflights.reqs);
        spin_unlock_irq(&rrpc->inflights.lock);
        return 0;
}

static inline int rrpc_lock_laddr(struct rrpc *rrpc, sector_t laddr,
                                 unsigned pages,
                                 struct rrpc_inflight_rq *r)
{
        BUG_ON((laddr + pages) > rrpc->nr_sects);

        return __rrpc_lock_laddr(rrpc, laddr, pages, r);
}

static inline struct rrpc_inflight_rq *rrpc_get_inflight_rq(struct nvm_rq *rqd)
{
        struct rrpc_rq *rrqd = nvm_rq_to_pdu(rqd);

        return &rrqd->inflight_rq;
}

static inline int rrpc_lock_rq(struct rrpc *rrpc, struct bio *bio,
                                                        struct nvm_rq *rqd)
{
        sector_t laddr = rrpc_get_laddr(bio);
        unsigned int pages = rrpc_get_pages(bio);
        struct rrpc_inflight_rq *r = rrpc_get_inflight_rq(rqd);

        return rrpc_lock_laddr(rrpc, laddr, pages, r);
}

static inline void rrpc_unlock_laddr(struct rrpc *rrpc,
                                                struct rrpc_inflight_rq *r)
{
        unsigned long flags;

        spin_lock_irqsave(&rrpc->inflights.lock, flags);
        list_del_init(&r->list);
        spin_unlock_irqrestore(&rrpc->inflights.lock, flags);
}

static inline void rrpc_unlock_rq(struct rrpc *rrpc, struct nvm_rq *rqd)
{
        struct rrpc_inflight_rq *r = rrpc_get_inflight_rq(rqd);
        uint8_t pages = rqd->nr_pages;

        BUG_ON((r->l_start + pages) > rrpc->nr_sects);

        rrpc_unlock_laddr(rrpc, r);
}

#endif /* RRPC_H_ */