/*
 * 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.
 */

#include "rrpc.h"

static struct kmem_cache *rrpc_gcb_cache, *rrpc_rq_cache;
static DECLARE_RWSEM(rrpc_lock);

static int rrpc_submit_io(struct rrpc *rrpc, struct bio *bio,
                                struct nvm_rq *rqd, unsigned long flags);

#define rrpc_for_each_lun(rrpc, rlun, i) \
                for ((i) = 0, rlun = &(rrpc)->luns[0]; \
                        (i) < (rrpc)->nr_luns; (i)++, rlun = &(rrpc)->luns[(i)])

static void rrpc_page_invalidate(struct rrpc *rrpc, struct rrpc_addr *a)
{
        struct rrpc_block *rblk = a->rblk;
        unsigned int pg_offset;

        lockdep_assert_held(&rrpc->rev_lock);

        if (a->addr == ADDR_EMPTY || !rblk)
                return;

        spin_lock(&rblk->lock);

        div_u64_rem(a->addr, rrpc->dev->sec_per_blk, &pg_offset);
        WARN_ON(test_and_set_bit(pg_offset, rblk->invalid_pages));
        rblk->nr_invalid_pages++;

        spin_unlock(&rblk->lock);

        rrpc->rev_trans_map[a->addr - rrpc->poffset].addr = ADDR_EMPTY;
}

static void rrpc_invalidate_range(struct rrpc *rrpc, sector_t slba,
                                                        unsigned int len)
{
        sector_t i;

        spin_lock(&rrpc->rev_lock);
        for (i = slba; i < slba + len; i++) {
                struct rrpc_addr *gp = &rrpc->trans_map[i];

                rrpc_page_invalidate(rrpc, gp);
                gp->rblk = NULL;
        }
        spin_unlock(&rrpc->rev_lock);
}

static struct nvm_rq *rrpc_inflight_laddr_acquire(struct rrpc *rrpc,
                                        sector_t laddr, unsigned int pages)
{
        struct nvm_rq *rqd;
        struct rrpc_inflight_rq *inf;

        rqd = mempool_alloc(rrpc->rq_pool, GFP_ATOMIC);
        if (!rqd)
                return ERR_PTR(-ENOMEM);

        inf = rrpc_get_inflight_rq(rqd);
        if (rrpc_lock_laddr(rrpc, laddr, pages, inf)) {
                mempool_free(rqd, rrpc->rq_pool);
                return NULL;
        }

        return rqd;
}

static void rrpc_inflight_laddr_release(struct rrpc *rrpc, struct nvm_rq *rqd)
{
        struct rrpc_inflight_rq *inf = rrpc_get_inflight_rq(rqd);

        rrpc_unlock_laddr(rrpc, inf);

        mempool_free(rqd, rrpc->rq_pool);
}

static void rrpc_discard(struct rrpc *rrpc, struct bio *bio)
{
        sector_t slba = bio->bi_iter.bi_sector / NR_PHY_IN_LOG;
        sector_t len = bio->bi_iter.bi_size / RRPC_EXPOSED_PAGE_SIZE;
        struct nvm_rq *rqd;

        while (1) {
                rqd = rrpc_inflight_laddr_acquire(rrpc, slba, len);
                if (rqd)
                        break;

                schedule();
        }

        if (IS_ERR(rqd)) {
                pr_err("rrpc: unable to acquire inflight IO\n");
                bio_io_error(bio);
                return;
        }

        rrpc_invalidate_range(rrpc, slba, len);
        rrpc_inflight_laddr_release(rrpc, rqd);
}

static int block_is_full(struct rrpc *rrpc, struct rrpc_block *rblk)
{
        return (rblk->next_page == rrpc->dev->sec_per_blk);
}

/* Calculate relative addr for the given block, considering instantiated LUNs */
static u64 block_to_rel_addr(struct rrpc *rrpc, struct rrpc_block *rblk)
{
        struct nvm_block *blk = rblk->parent;
        int lun_blk = blk->id % (rrpc->dev->blks_per_lun * rrpc->nr_luns);

        return lun_blk * rrpc->dev->sec_per_blk;
}

/* Calculate global addr for the given block */
static u64 block_to_addr(struct rrpc *rrpc, struct rrpc_block *rblk)
{
        struct nvm_block *blk = rblk->parent;

        return blk->id * rrpc->dev->sec_per_blk;
}

static struct ppa_addr linear_to_generic_addr(struct nvm_dev *dev,
                                                        struct ppa_addr r)
{
        struct ppa_addr l;
        int secs, pgs, blks, luns;
        sector_t ppa = r.ppa;

        l.ppa = 0;

        div_u64_rem(ppa, dev->sec_per_pg, &secs);
        l.g.sec = secs;

        sector_div(ppa, dev->sec_per_pg);
        div_u64_rem(ppa, dev->pgs_per_blk, &pgs);
        l.g.pg = pgs;

        sector_div(ppa, dev->pgs_per_blk);
        div_u64_rem(ppa, dev->blks_per_lun, &blks);
        l.g.blk = blks;

        sector_div(ppa, dev->blks_per_lun);
        div_u64_rem(ppa, dev->luns_per_chnl, &luns);
        l.g.lun = luns;

        sector_div(ppa, dev->luns_per_chnl);
        l.g.ch = ppa;

        return l;
}

static struct ppa_addr rrpc_ppa_to_gaddr(struct nvm_dev *dev, u64 addr)
{
        struct ppa_addr paddr;

        paddr.ppa = addr;
        return linear_to_generic_addr(dev, paddr);
}

/* requires lun->lock taken */
static void rrpc_set_lun_cur(struct rrpc_lun *rlun, struct rrpc_block *new_rblk,
                                                struct rrpc_block **cur_rblk)
{
        struct rrpc *rrpc = rlun->rrpc;

        if (*cur_rblk) {
                spin_lock(&(*cur_rblk)->lock);
                WARN_ON(!block_is_full(rrpc, *cur_rblk));
                spin_unlock(&(*cur_rblk)->lock);
        }
        *cur_rblk = new_rblk;
}

static struct rrpc_block *rrpc_get_blk(struct rrpc *rrpc, struct rrpc_lun *rlun,
                                                        unsigned long flags)
{
        struct nvm_block *blk;
        struct rrpc_block *rblk;

        blk = nvm_get_blk(rrpc->dev, rlun->parent, flags);
        if (!blk) {
                pr_err("nvm: rrpc: cannot get new block from media manager\n");
                return NULL;
        }

        rblk = rrpc_get_rblk(rlun, blk->id);
        blk->priv = rblk;
        bitmap_zero(rblk->invalid_pages, rrpc->dev->sec_per_blk);
        rblk->next_page = 0;
        rblk->nr_invalid_pages = 0;
        atomic_set(&rblk->data_cmnt_size, 0);

        return rblk;
}

static void rrpc_put_blk(struct rrpc *rrpc, struct rrpc_block *rblk)
{
        nvm_put_blk(rrpc->dev, rblk->parent);
}

static void rrpc_put_blks(struct rrpc *rrpc)
{
        struct rrpc_lun *rlun;
        int i;

        for (i = 0; i < rrpc->nr_luns; i++) {
                rlun = &rrpc->luns[i];
                if (rlun->cur)
                        rrpc_put_blk(rrpc, rlun->cur);
                if (rlun->gc_cur)
                        rrpc_put_blk(rrpc, rlun->gc_cur);
        }
}

static struct rrpc_lun *get_next_lun(struct rrpc *rrpc)
{
        int next = atomic_inc_return(&rrpc->next_lun);

        return &rrpc->luns[next % rrpc->nr_luns];
}

static void rrpc_gc_kick(struct rrpc *rrpc)
{
        struct rrpc_lun *rlun;
        unsigned int i;

        for (i = 0; i < rrpc->nr_luns; i++) {
                rlun = &rrpc->luns[i];
                queue_work(rrpc->krqd_wq, &rlun->ws_gc);
        }
}

/*
 * timed GC every interval.
 */
static void rrpc_gc_timer(unsigned long data)
{
        struct rrpc *rrpc = (struct rrpc *)data;

        rrpc_gc_kick(rrpc);
        mod_timer(&rrpc->gc_timer, jiffies + msecs_to_jiffies(10));
}

static void rrpc_end_sync_bio(struct bio *bio)
{
        struct completion *waiting = bio->bi_private;

        if (bio->bi_error)
                pr_err("nvm: gc request failed (%u).\n", bio->bi_error);

        complete(waiting);
}

/*
 * rrpc_move_valid_pages -- migrate live data off the block
 * @rrpc: the 'rrpc' structure
 * @block: the block from which to migrate live pages
 *
 * Description:
 *   GC algorithms may call this function to migrate remaining live
 *   pages off the block prior to erasing it. This function blocks
 *   further execution until the operation is complete.
 */
static int rrpc_move_valid_pages(struct rrpc *rrpc, struct rrpc_block *rblk)
{
        struct request_queue *q = rrpc->dev->q;
        struct rrpc_rev_addr *rev;
        struct nvm_rq *rqd;
        struct bio *bio;
        struct page *page;
        int slot;
        int nr_sec_per_blk = rrpc->dev->sec_per_blk;
        u64 phys_addr;
        DECLARE_COMPLETION_ONSTACK(wait);

        if (bitmap_full(rblk->invalid_pages, nr_sec_per_blk))
                return 0;

        bio = bio_alloc(GFP_NOIO, 1);
        if (!bio) {
                pr_err("nvm: could not alloc bio to gc\n");
                return -ENOMEM;
        }

        page = mempool_alloc(rrpc->page_pool, GFP_NOIO);
        if (!page) {
                bio_put(bio);
                return -ENOMEM;
        }

        while ((slot = find_first_zero_bit(rblk->invalid_pages,
                                            nr_sec_per_blk)) < nr_sec_per_blk) {

                /* Lock laddr */
                phys_addr = rblk->parent->id * nr_sec_per_blk + slot;

try:
                spin_lock(&rrpc->rev_lock);
                /* Get logical address from physical to logical table */
                rev = &rrpc->rev_trans_map[phys_addr - rrpc->poffset];
                /* already updated by previous regular write */
                if (rev->addr == ADDR_EMPTY) {
                        spin_unlock(&rrpc->rev_lock);
                        continue;
                }

                rqd = rrpc_inflight_laddr_acquire(rrpc, rev->addr, 1);
                if (IS_ERR_OR_NULL(rqd)) {
                        spin_unlock(&rrpc->rev_lock);
                        schedule();
                        goto try;
                }

                spin_unlock(&rrpc->rev_lock);

                /* Perform read to do GC */
                bio->bi_iter.bi_sector = rrpc_get_sector(rev->addr);
                bio_set_op_attrs(bio,  REQ_OP_READ, 0);
                bio->bi_private = &wait;
                bio->bi_end_io = rrpc_end_sync_bio;

                /* TODO: may fail when EXP_PG_SIZE > PAGE_SIZE */
                bio_add_pc_page(q, bio, page, RRPC_EXPOSED_PAGE_SIZE, 0);

                if (rrpc_submit_io(rrpc, bio, rqd, NVM_IOTYPE_GC)) {
                        pr_err("rrpc: gc read failed.\n");
                        rrpc_inflight_laddr_release(rrpc, rqd);
                        goto finished;
                }
                wait_for_completion_io(&wait);
                if (bio->bi_error) {
                        rrpc_inflight_laddr_release(rrpc, rqd);
                        goto finished;
                }

                bio_reset(bio);
                reinit_completion(&wait);

                bio->bi_iter.bi_sector = rrpc_get_sector(rev->addr);
                bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
                bio->bi_private = &wait;
                bio->bi_end_io = rrpc_end_sync_bio;

                bio_add_pc_page(q, bio, page, RRPC_EXPOSED_PAGE_SIZE, 0);

                /* turn the command around and write the data back to a new
                 * address
                 */
                if (rrpc_submit_io(rrpc, bio, rqd, NVM_IOTYPE_GC)) {
                        pr_err("rrpc: gc write failed.\n");
                        rrpc_inflight_laddr_release(rrpc, rqd);
                        goto finished;
                }
                wait_for_completion_io(&wait);

                rrpc_inflight_laddr_release(rrpc, rqd);
                if (bio->bi_error)
                        goto finished;

                bio_reset(bio);
        }

finished:
        mempool_free(page, rrpc->page_pool);
        bio_put(bio);

        if (!bitmap_full(rblk->invalid_pages, nr_sec_per_blk)) {
                pr_err("nvm: failed to garbage collect block\n");
                return -EIO;
        }

        return 0;
}

static void rrpc_block_gc(struct work_struct *work)
{
        struct rrpc_block_gc *gcb = container_of(work, struct rrpc_block_gc,
                                                                        ws_gc);
        struct rrpc *rrpc = gcb->rrpc;
        struct rrpc_block *rblk = gcb->rblk;
        struct rrpc_lun *rlun = rblk->rlun;
        struct nvm_dev *dev = rrpc->dev;

        mempool_free(gcb, rrpc->gcb_pool);
        pr_debug("nvm: block '%lu' being reclaimed\n", rblk->parent->id);

        if (rrpc_move_valid_pages(rrpc, rblk))
                goto put_back;

        if (nvm_erase_blk(dev, rblk->parent))
                goto put_back;

        rrpc_put_blk(rrpc, rblk);

        return;

put_back:
        spin_lock(&rlun->lock);
        list_add_tail(&rblk->prio, &rlun->prio_list);
        spin_unlock(&rlun->lock);
}

/* the block with highest number of invalid pages, will be in the beginning
 * of the list
 */
static struct rrpc_block *rblock_max_invalid(struct rrpc_block *ra,
                                                        struct rrpc_block *rb)
{
        if (ra->nr_invalid_pages == rb->nr_invalid_pages)
                return ra;

        return (ra->nr_invalid_pages < rb->nr_invalid_pages) ? rb : ra;
}

/* linearly find the block with highest number of invalid pages
 * requires lun->lock
 */
static struct rrpc_block *block_prio_find_max(struct rrpc_lun *rlun)
{
        struct list_head *prio_list = &rlun->prio_list;
        struct rrpc_block *rblock, *max;

        BUG_ON(list_empty(prio_list));

        max = list_first_entry(prio_list, struct rrpc_block, prio);
        list_for_each_entry(rblock, prio_list, prio)
                max = rblock_max_invalid(max, rblock);

        return max;
}

static void rrpc_lun_gc(struct work_struct *work)
{
        struct rrpc_lun *rlun = container_of(work, struct rrpc_lun, ws_gc);
        struct rrpc *rrpc = rlun->rrpc;
        struct nvm_lun *lun = rlun->parent;
        struct rrpc_block_gc *gcb;
        unsigned int nr_blocks_need;

        nr_blocks_need = rrpc->dev->blks_per_lun / GC_LIMIT_INVERSE;

        if (nr_blocks_need < rrpc->nr_luns)
                nr_blocks_need = rrpc->nr_luns;

        spin_lock(&rlun->lock);
        while (nr_blocks_need > lun->nr_free_blocks &&
                                        !list_empty(&rlun->prio_list)) {
                struct rrpc_block *rblock = block_prio_find_max(rlun);
                struct nvm_block *block = rblock->parent;

                if (!rblock->nr_invalid_pages)
                        break;

                gcb = mempool_alloc(rrpc->gcb_pool, GFP_ATOMIC);
                if (!gcb)
                        break;

                list_del_init(&rblock->prio);

                BUG_ON(!block_is_full(rrpc, rblock));

                pr_debug("rrpc: selected block '%lu' for GC\n", block->id);

                gcb->rrpc = rrpc;
                gcb->rblk = rblock;
                INIT_WORK(&gcb->ws_gc, rrpc_block_gc);

                queue_work(rrpc->kgc_wq, &gcb->ws_gc);

                nr_blocks_need--;
        }
        spin_unlock(&rlun->lock);

        /* TODO: Hint that request queue can be started again */
}

static void rrpc_gc_queue(struct work_struct *work)
{
        struct rrpc_block_gc *gcb = container_of(work, struct rrpc_block_gc,
                                                                        ws_gc);
        struct rrpc *rrpc = gcb->rrpc;
        struct rrpc_block *rblk = gcb->rblk;
        struct rrpc_lun *rlun = rblk->rlun;

        spin_lock(&rlun->lock);
        list_add_tail(&rblk->prio, &rlun->prio_list);
        spin_unlock(&rlun->lock);

        mempool_free(gcb, rrpc->gcb_pool);
        pr_debug("nvm: block '%lu' is full, allow GC (sched)\n",
                                                        rblk->parent->id);
}

static const struct block_device_operations rrpc_fops = {
        .owner          = THIS_MODULE,
};

static struct rrpc_lun *rrpc_get_lun_rr(struct rrpc *rrpc, int is_gc)
{
        unsigned int i;
        struct rrpc_lun *rlun, *max_free;

        if (!is_gc)
                return get_next_lun(rrpc);

        /* during GC, we don't care about RR, instead we want to make
         * sure that we maintain evenness between the block luns.
         */
        max_free = &rrpc->luns[0];
        /* prevent GC-ing lun from devouring pages of a lun with
         * little free blocks. We don't take the lock as we only need an
         * estimate.
         */
        rrpc_for_each_lun(rrpc, rlun, i) {
                if (rlun->parent->nr_free_blocks >
                                        max_free->parent->nr_free_blocks)
                        max_free = rlun;
        }

        return max_free;
}

static struct rrpc_addr *rrpc_update_map(struct rrpc *rrpc, sector_t laddr,
                                        struct rrpc_block *rblk, u64 paddr)
{
        struct rrpc_addr *gp;
        struct rrpc_rev_addr *rev;

        BUG_ON(laddr >= rrpc->nr_sects);

        gp = &rrpc->trans_map[laddr];
        spin_lock(&rrpc->rev_lock);
        if (gp->rblk)
                rrpc_page_invalidate(rrpc, gp);

        gp->addr = paddr;
        gp->rblk = rblk;

        rev = &rrpc->rev_trans_map[gp->addr - rrpc->poffset];
        rev->addr = laddr;
        spin_unlock(&rrpc->rev_lock);

        return gp;
}

static u64 rrpc_alloc_addr(struct rrpc *rrpc, struct rrpc_block *rblk)
{
        u64 addr = ADDR_EMPTY;

        spin_lock(&rblk->lock);
        if (block_is_full(rrpc, rblk))
                goto out;

        addr = block_to_addr(rrpc, rblk) + rblk->next_page;

        rblk->next_page++;
out:
        spin_unlock(&rblk->lock);
        return addr;
}

/* Map logical address to a physical page. The mapping implements a round robin
 * approach and allocates a page from the next lun available.
 *
 * Returns rrpc_addr with the physical address and block. Returns NULL if no
 * blocks in the next rlun are available.
 */
static struct rrpc_addr *rrpc_map_page(struct rrpc *rrpc, sector_t laddr,
                                                                int is_gc)
{
        struct rrpc_lun *rlun;
        struct rrpc_block *rblk, **cur_rblk;
        struct nvm_lun *lun;
        u64 paddr;
        int gc_force = 0;

        rlun = rrpc_get_lun_rr(rrpc, is_gc);
        lun = rlun->parent;

        if (!is_gc && lun->nr_free_blocks < rrpc->nr_luns * 4)
                return NULL;

        /*
         * page allocation steps:
         * 1. Try to allocate new page from current rblk
         * 2a. If succeed, proceed to map it in and return
         * 2b. If fail, first try to allocate a new block from media manger,
         *     and then retry step 1. Retry until the normal block pool is
         *     exhausted.
         * 3. If exhausted, and garbage collector is requesting the block,
         *    go to the reserved block and retry step 1.
         *    In the case that this fails as well, or it is not GC
         *    requesting, report not able to retrieve a block and let the
         *    caller handle further processing.
         */

        spin_lock(&rlun->lock);
        cur_rblk = &rlun->cur;
        rblk = rlun->cur;
retry:
        paddr = rrpc_alloc_addr(rrpc, rblk);

        if (paddr != ADDR_EMPTY)
                goto done;

        if (!list_empty(&rlun->wblk_list)) {
new_blk:
                rblk = list_first_entry(&rlun->wblk_list, struct rrpc_block,
                                                                        prio);
                rrpc_set_lun_cur(rlun, rblk, cur_rblk);
                list_del(&rblk->prio);
                goto retry;
        }
        spin_unlock(&rlun->lock);

        rblk = rrpc_get_blk(rrpc, rlun, gc_force);
        if (rblk) {
                spin_lock(&rlun->lock);
                list_add_tail(&rblk->prio, &rlun->wblk_list);
                /*
                 * another thread might already have added a new block,
                 * Therefore, make sure that one is used, instead of the
                 * one just added.
                 */
                goto new_blk;
        }

        if (unlikely(is_gc) && !gc_force) {
                /* retry from emergency gc block */
                cur_rblk = &rlun->gc_cur;
                rblk = rlun->gc_cur;
                gc_force = 1;
                spin_lock(&rlun->lock);
                goto retry;
        }

        pr_err("rrpc: failed to allocate new block\n");
        return NULL;
done:
        spin_unlock(&rlun->lock);
        return rrpc_update_map(rrpc, laddr, rblk, paddr);
}

static void rrpc_run_gc(struct rrpc *rrpc, struct rrpc_block *rblk)
{
        struct rrpc_block_gc *gcb;

        gcb = mempool_alloc(rrpc->gcb_pool, GFP_ATOMIC);
        if (!gcb) {
                pr_err("rrpc: unable to queue block for gc.");
                return;
        }

        gcb->rrpc = rrpc;
        gcb->rblk = rblk;

        INIT_WORK(&gcb->ws_gc, rrpc_gc_queue);
        queue_work(rrpc->kgc_wq, &gcb->ws_gc);
}

static void rrpc_end_io_write(struct rrpc *rrpc, struct rrpc_rq *rrqd,
                                                sector_t laddr, uint8_t npages)
{
        struct rrpc_addr *p;
        struct rrpc_block *rblk;
        struct nvm_lun *lun;
        int cmnt_size, i;

        for (i = 0; i < npages; i++) {
                p = &rrpc->trans_map[laddr + i];
                rblk = p->rblk;
                lun = rblk->parent->lun;

                cmnt_size = atomic_inc_return(&rblk->data_cmnt_size);
                if (unlikely(cmnt_size == rrpc->dev->sec_per_blk))
                        rrpc_run_gc(rrpc, rblk);
        }
}

static void rrpc_end_io(struct nvm_rq *rqd)
{
        struct rrpc *rrpc = container_of(rqd->ins, struct rrpc, instance);
        struct rrpc_rq *rrqd = nvm_rq_to_pdu(rqd);
        uint8_t npages = rqd->nr_ppas;
        sector_t laddr = rrpc_get_laddr(rqd->bio) - npages;

        if (bio_data_dir(rqd->bio) == WRITE)
                rrpc_end_io_write(rrpc, rrqd, laddr, npages);

        bio_put(rqd->bio);

        if (rrqd->flags & NVM_IOTYPE_GC)
                return;

        rrpc_unlock_rq(rrpc, rqd);

        if (npages > 1)
                nvm_dev_dma_free(rrpc->dev, rqd->ppa_list, rqd->dma_ppa_list);

        mempool_free(rqd, rrpc->rq_pool);
}

static int rrpc_read_ppalist_rq(struct rrpc *rrpc, struct bio *bio,
                        struct nvm_rq *rqd, unsigned long flags, int npages)
{
        struct rrpc_inflight_rq *r = rrpc_get_inflight_rq(rqd);
        struct rrpc_addr *gp;
        sector_t laddr = rrpc_get_laddr(bio);
        int is_gc = flags & NVM_IOTYPE_GC;
        int i;

        if (!is_gc && rrpc_lock_rq(rrpc, bio, rqd)) {
                nvm_dev_dma_free(rrpc->dev, rqd->ppa_list, rqd->dma_ppa_list);
                return NVM_IO_REQUEUE;
        }

        for (i = 0; i < npages; i++) {
                /* We assume that mapping occurs at 4KB granularity */
                BUG_ON(!(laddr + i >= 0 && laddr + i < rrpc->nr_sects));
                gp = &rrpc->trans_map[laddr + i];

                if (gp->rblk) {
                        rqd->ppa_list[i] = rrpc_ppa_to_gaddr(rrpc->dev,
                                                                gp->addr);
                } else {
                        BUG_ON(is_gc);
                        rrpc_unlock_laddr(rrpc, r);
                        nvm_dev_dma_free(rrpc->dev, rqd->ppa_list,
                                                        rqd->dma_ppa_list);
                        return NVM_IO_DONE;
                }
        }

        rqd->opcode = NVM_OP_HBREAD;

        return NVM_IO_OK;
}

static int rrpc_read_rq(struct rrpc *rrpc, struct bio *bio, struct nvm_rq *rqd,
                                                        unsigned long flags)
{
        struct rrpc_rq *rrqd = nvm_rq_to_pdu(rqd);
        int is_gc = flags & NVM_IOTYPE_GC;
        sector_t laddr = rrpc_get_laddr(bio);
        struct rrpc_addr *gp;

        if (!is_gc && rrpc_lock_rq(rrpc, bio, rqd))
                return NVM_IO_REQUEUE;

        BUG_ON(!(laddr >= 0 && laddr < rrpc->nr_sects));
        gp = &rrpc->trans_map[laddr];

        if (gp->rblk) {
                rqd->ppa_addr = rrpc_ppa_to_gaddr(rrpc->dev, gp->addr);
        } else {
                BUG_ON(is_gc);
                rrpc_unlock_rq(rrpc, rqd);
                return NVM_IO_DONE;
        }

        rqd->opcode = NVM_OP_HBREAD;
        rrqd->addr = gp;

        return NVM_IO_OK;
}

static int rrpc_write_ppalist_rq(struct rrpc *rrpc, struct bio *bio,
                        struct nvm_rq *rqd, unsigned long flags, int npages)
{
        struct rrpc_inflight_rq *r = rrpc_get_inflight_rq(rqd);
        struct rrpc_addr *p;
        sector_t laddr = rrpc_get_laddr(bio);
        int is_gc = flags & NVM_IOTYPE_GC;
        int i;

        if (!is_gc && rrpc_lock_rq(rrpc, bio, rqd)) {
                nvm_dev_dma_free(rrpc->dev, rqd->ppa_list, rqd->dma_ppa_list);
                return NVM_IO_REQUEUE;
        }

        for (i = 0; i < npages; i++) {
                /* We assume that mapping occurs at 4KB granularity */
                p = rrpc_map_page(rrpc, laddr + i, is_gc);
                if (!p) {
                        BUG_ON(is_gc);
                        rrpc_unlock_laddr(rrpc, r);
                        nvm_dev_dma_free(rrpc->dev, rqd->ppa_list,
                                                        rqd->dma_ppa_list);
                        rrpc_gc_kick(rrpc);
                        return NVM_IO_REQUEUE;
                }

                rqd->ppa_list[i] = rrpc_ppa_to_gaddr(rrpc->dev,
                                                                p->addr);
        }

        rqd->opcode = NVM_OP_HBWRITE;

        return NVM_IO_OK;
}

static int rrpc_write_rq(struct rrpc *rrpc, struct bio *bio,
                                struct nvm_rq *rqd, unsigned long flags)
{
        struct rrpc_rq *rrqd = nvm_rq_to_pdu(rqd);
        struct rrpc_addr *p;
        int is_gc = flags & NVM_IOTYPE_GC;
        sector_t laddr = rrpc_get_laddr(bio);

        if (!is_gc && rrpc_lock_rq(rrpc, bio, rqd))
                return NVM_IO_REQUEUE;

        p = rrpc_map_page(rrpc, laddr, is_gc);
        if (!p) {
                BUG_ON(is_gc);
                rrpc_unlock_rq(rrpc, rqd);
                rrpc_gc_kick(rrpc);
                return NVM_IO_REQUEUE;
        }

        rqd->ppa_addr = rrpc_ppa_to_gaddr(rrpc->dev, p->addr);
        rqd->opcode = NVM_OP_HBWRITE;
        rrqd->addr = p;

        return NVM_IO_OK;
}

static int rrpc_setup_rq(struct rrpc *rrpc, struct bio *bio,
                        struct nvm_rq *rqd, unsigned long flags, uint8_t npages)
{
        if (npages > 1) {
                rqd->ppa_list = nvm_dev_dma_alloc(rrpc->dev, GFP_KERNEL,
                                                        &rqd->dma_ppa_list);
                if (!rqd->ppa_list) {
                        pr_err("rrpc: not able to allocate ppa list\n");
                        return NVM_IO_ERR;
                }

                if (bio_op(bio) == REQ_OP_WRITE)
                        return rrpc_write_ppalist_rq(rrpc, bio, rqd, flags,
                                                                        npages);

                return rrpc_read_ppalist_rq(rrpc, bio, rqd, flags, npages);
        }

        if (bio_op(bio) == REQ_OP_WRITE)
                return rrpc_write_rq(rrpc, bio, rqd, flags);

        return rrpc_read_rq(rrpc, bio, rqd, flags);
}

static int rrpc_submit_io(struct rrpc *rrpc, struct bio *bio,
                                struct nvm_rq *rqd, unsigned long flags)
{
        int err;
        struct rrpc_rq *rrq = nvm_rq_to_pdu(rqd);
        uint8_t nr_pages = rrpc_get_pages(bio);
        int bio_size = bio_sectors(bio) << 9;

        if (bio_size < rrpc->dev->sec_size)
                return NVM_IO_ERR;
        else if (bio_size > rrpc->dev->max_rq_size)
                return NVM_IO_ERR;

        err = rrpc_setup_rq(rrpc, bio, rqd, flags, nr_pages);
        if (err)
                return err;

        bio_get(bio);
        rqd->bio = bio;
        rqd->ins = &rrpc->instance;
        rqd->nr_ppas = nr_pages;
        rrq->flags = flags;

        err = nvm_submit_io(rrpc->dev, rqd);
        if (err) {
                pr_err("rrpc: I/O submission failed: %d\n", err);
                bio_put(bio);
                if (!(flags & NVM_IOTYPE_GC)) {
                        rrpc_unlock_rq(rrpc, rqd);
                        if (rqd->nr_ppas > 1)
                                nvm_dev_dma_free(rrpc->dev,
                        rqd->ppa_list, rqd->dma_ppa_list);
                }
                return NVM_IO_ERR;
        }

        return NVM_IO_OK;
}

static blk_qc_t rrpc_make_rq(struct request_queue *q, struct bio *bio)
{
        struct rrpc *rrpc = q->queuedata;
        struct nvm_rq *rqd;
        int err;

        if (bio_op(bio) == REQ_OP_DISCARD) {
                rrpc_discard(rrpc, bio);
                return BLK_QC_T_NONE;
        }

        rqd = mempool_alloc(rrpc->rq_pool, GFP_KERNEL);
        if (!rqd) {
                pr_err_ratelimited("rrpc: not able to queue bio.");
                bio_io_error(bio);
                return BLK_QC_T_NONE;
        }
        memset(rqd, 0, sizeof(struct nvm_rq));

        err = rrpc_submit_io(rrpc, bio, rqd, NVM_IOTYPE_NONE);
        switch (err) {
        case NVM_IO_OK:
                return BLK_QC_T_NONE;
        case NVM_IO_ERR:
                bio_io_error(bio);
                break;
        case NVM_IO_DONE:
                bio_endio(bio);
                break;
        case NVM_IO_REQUEUE:
                spin_lock(&rrpc->bio_lock);
                bio_list_add(&rrpc->requeue_bios, bio);
                spin_unlock(&rrpc->bio_lock);
                queue_work(rrpc->kgc_wq, &rrpc->ws_requeue);
                break;
        }

        mempool_free(rqd, rrpc->rq_pool);
        return BLK_QC_T_NONE;
}

static void rrpc_requeue(struct work_struct *work)
{
        struct rrpc *rrpc = container_of(work, struct rrpc, ws_requeue);
        struct bio_list bios;
        struct bio *bio;

        bio_list_init(&bios);

        spin_lock(&rrpc->bio_lock);
        bio_list_merge(&bios, &rrpc->requeue_bios);
        bio_list_init(&rrpc->requeue_bios);
        spin_unlock(&rrpc->bio_lock);

        while ((bio = bio_list_pop(&bios)))
                rrpc_make_rq(rrpc->disk->queue, bio);
}

static void rrpc_gc_free(struct rrpc *rrpc)
{
        if (rrpc->krqd_wq)
                destroy_workqueue(rrpc->krqd_wq);

        if (rrpc->kgc_wq)
                destroy_workqueue(rrpc->kgc_wq);
}

static int rrpc_gc_init(struct rrpc *rrpc)
{
        rrpc->krqd_wq = alloc_workqueue("rrpc-lun", WQ_MEM_RECLAIM|WQ_UNBOUND,
                                                                rrpc->nr_luns);
        if (!rrpc->krqd_wq)
                return -ENOMEM;

        rrpc->kgc_wq = alloc_workqueue("rrpc-bg", WQ_MEM_RECLAIM, 1);
        if (!rrpc->kgc_wq)
                return -ENOMEM;

        setup_timer(&rrpc->gc_timer, rrpc_gc_timer, (unsigned long)rrpc);

        return 0;
}

static void rrpc_map_free(struct rrpc *rrpc)
{
        vfree(rrpc->rev_trans_map);
        vfree(rrpc->trans_map);
}

static int rrpc_l2p_update(u64 slba, u32 nlb, __le64 *entries, void *private)
{
        struct rrpc *rrpc = (struct rrpc *)private;
        struct nvm_dev *dev = rrpc->dev;

        struct rrpc_addr *addr = rrpc->trans_map + slba;
        struct rrpc_rev_addr *raddr = rrpc->rev_trans_map;
        u64 elba = slba + nlb;
        u64 i;

        if (unlikely(elba > dev->total_secs)) {
                pr_err("nvm: L2P data from device is out of bounds!\n");
                return -EINVAL;
        }

        for (i = 0; i < nlb; i++) {
                u64 pba = le64_to_cpu(entries[i]);
                unsigned int mod;
                /* LNVM treats address-spaces as silos, LBA and PBA are
                 * equally large and zero-indexed.
                 */
                if (unlikely(pba >= dev->total_secs && pba != U64_MAX)) {
                        pr_err("nvm: L2P data entry is out of bounds!\n");
                        return -EINVAL;
                }

                /* Address zero is a special one. The first page on a disk is
                 * protected. As it often holds internal device boot
                 * information.
                 */
                if (!pba)
                        continue;

                div_u64_rem(pba, rrpc->nr_sects, &mod);

                addr[i].addr = pba;
                raddr[mod].addr = slba + i;
        }

        return 0;
}

static int rrpc_map_init(struct rrpc *rrpc)
{
        struct nvm_dev *dev = rrpc->dev;
        sector_t i;
        int ret;

        rrpc->trans_map = vzalloc(sizeof(struct rrpc_addr) * rrpc->nr_sects);
        if (!rrpc->trans_map)
                return -ENOMEM;

        rrpc->rev_trans_map = vmalloc(sizeof(struct rrpc_rev_addr)
                                                        * rrpc->nr_sects);
        if (!rrpc->rev_trans_map)
                return -ENOMEM;

        for (i = 0; i < rrpc->nr_sects; i++) {
                struct rrpc_addr *p = &rrpc->trans_map[i];
                struct rrpc_rev_addr *r = &rrpc->rev_trans_map[i];

                p->addr = ADDR_EMPTY;
                r->addr = ADDR_EMPTY;
        }

        if (!dev->ops->get_l2p_tbl)
                return 0;

        /* Bring up the mapping table from device */
        ret = dev->ops->get_l2p_tbl(dev, rrpc->soffset, rrpc->nr_sects,
                                        rrpc_l2p_update, rrpc);
        if (ret) {
                pr_err("nvm: rrpc: could not read L2P table.\n");
                return -EINVAL;
        }

        return 0;
}

/* Minimum pages needed within a lun */
#define PAGE_POOL_SIZE 16
#define ADDR_POOL_SIZE 64

static int rrpc_core_init(struct rrpc *rrpc)
{
        down_write(&rrpc_lock);
        if (!rrpc_gcb_cache) {
                rrpc_gcb_cache = kmem_cache_create("rrpc_gcb",
                                sizeof(struct rrpc_block_gc), 0, 0, NULL);
                if (!rrpc_gcb_cache) {
                        up_write(&rrpc_lock);
                        return -ENOMEM;
                }

                rrpc_rq_cache = kmem_cache_create("rrpc_rq",
                                sizeof(struct nvm_rq) + sizeof(struct rrpc_rq),
                                0, 0, NULL);
                if (!rrpc_rq_cache) {
                        kmem_cache_destroy(rrpc_gcb_cache);
                        up_write(&rrpc_lock);
                        return -ENOMEM;
                }
        }
        up_write(&rrpc_lock);

        rrpc->page_pool = mempool_create_page_pool(PAGE_POOL_SIZE, 0);
        if (!rrpc->page_pool)
                return -ENOMEM;

        rrpc->gcb_pool = mempool_create_slab_pool(rrpc->dev->nr_luns,
                                                                rrpc_gcb_cache);
        if (!rrpc->gcb_pool)
                return -ENOMEM;

        rrpc->rq_pool = mempool_create_slab_pool(64, rrpc_rq_cache);
        if (!rrpc->rq_pool)
                return -ENOMEM;

        spin_lock_init(&rrpc->inflights.lock);
        INIT_LIST_HEAD(&rrpc->inflights.reqs);

        return 0;
}

static void rrpc_core_free(struct rrpc *rrpc)
{
        mempool_destroy(rrpc->page_pool);
        mempool_destroy(rrpc->gcb_pool);
        mempool_destroy(rrpc->rq_pool);
}

static void rrpc_luns_free(struct rrpc *rrpc)
{
        struct nvm_dev *dev = rrpc->dev;
        struct nvm_lun *lun;
        struct rrpc_lun *rlun;
        int i;

        if (!rrpc->luns)
                return;

        for (i = 0; i < rrpc->nr_luns; i++) {
                rlun = &rrpc->luns[i];
                lun = rlun->parent;
                if (!lun)
                        break;
                dev->mt->release_lun(dev, lun->id);
                vfree(rlun->blocks);
        }

        kfree(rrpc->luns);
}

static int rrpc_luns_init(struct rrpc *rrpc, int lun_begin, int lun_end)
{
        struct nvm_dev *dev = rrpc->dev;
        struct rrpc_lun *rlun;
        int i, j, ret = -EINVAL;

        if (dev->sec_per_blk > MAX_INVALID_PAGES_STORAGE * BITS_PER_LONG) {
                pr_err("rrpc: number of pages per block too high.");
                return -EINVAL;
        }

        spin_lock_init(&rrpc->rev_lock);

        rrpc->luns = kcalloc(rrpc->nr_luns, sizeof(struct rrpc_lun),
                                                                GFP_KERNEL);
        if (!rrpc->luns)
                return -ENOMEM;

        /* 1:1 mapping */
        for (i = 0; i < rrpc->nr_luns; i++) {
                int lunid = lun_begin + i;
                struct nvm_lun *lun;

                if (dev->mt->reserve_lun(dev, lunid)) {
                        pr_err("rrpc: lun %u is already allocated\n", lunid);
                        goto err;
                }

                lun = dev->mt->get_lun(dev, lunid);
                if (!lun)
                        goto err;

                rlun = &rrpc->luns[i];
                rlun->parent = lun;
                rlun->blocks = vzalloc(sizeof(struct rrpc_block) *
                                                rrpc->dev->blks_per_lun);
                if (!rlun->blocks) {
                        ret = -ENOMEM;
                        goto err;
                }

                for (j = 0; j < rrpc->dev->blks_per_lun; j++) {
                        struct rrpc_block *rblk = &rlun->blocks[j];
                        struct nvm_block *blk = &lun->blocks[j];

                        rblk->parent = blk;
                        rblk->rlun = rlun;
                        INIT_LIST_HEAD(&rblk->prio);
                        spin_lock_init(&rblk->lock);
                }

                rlun->rrpc = rrpc;
                INIT_LIST_HEAD(&rlun->prio_list);
                INIT_LIST_HEAD(&rlun->wblk_list);

                INIT_WORK(&rlun->ws_gc, rrpc_lun_gc);
                spin_lock_init(&rlun->lock);
        }

        return 0;
err:
        return ret;
}

/* returns 0 on success and stores the beginning address in *begin */
static int rrpc_area_init(struct rrpc *rrpc, sector_t *begin)
{
        struct nvm_dev *dev = rrpc->dev;
        struct nvmm_type *mt = dev->mt;
        sector_t size = rrpc->nr_sects * dev->sec_size;
        int ret;

        size >>= 9;

        ret = mt->get_area(dev, begin, size);
        if (!ret)
                *begin >>= (ilog2(dev->sec_size) - 9);

        return ret;
}

static void rrpc_area_free(struct rrpc *rrpc)
{
        struct nvm_dev *dev = rrpc->dev;
        struct nvmm_type *mt = dev->mt;
        sector_t begin = rrpc->soffset << (ilog2(dev->sec_size) - 9);

        mt->put_area(dev, begin);
}

static void rrpc_free(struct rrpc *rrpc)
{
        rrpc_gc_free(rrpc);
        rrpc_map_free(rrpc);
        rrpc_core_free(rrpc);
        rrpc_luns_free(rrpc);
        rrpc_area_free(rrpc);

        kfree(rrpc);
}

static void rrpc_exit(void *private)
{
        struct rrpc *rrpc = private;

        del_timer(&rrpc->gc_timer);

        flush_workqueue(rrpc->krqd_wq);
        flush_workqueue(rrpc->kgc_wq);

        rrpc_free(rrpc);
}

static sector_t rrpc_capacity(void *private)
{
        struct rrpc *rrpc = private;
        struct nvm_dev *dev = rrpc->dev;
        sector_t reserved, provisioned;

        /* cur, gc, and two emergency blocks for each lun */
        reserved = rrpc->nr_luns * dev->sec_per_blk * 4;
        provisioned = rrpc->nr_sects - reserved;

        if (reserved > rrpc->nr_sects) {
                pr_err("rrpc: not enough space available to expose storage.\n");
                return 0;
        }

        sector_div(provisioned, 10);
        return provisioned * 9 * NR_PHY_IN_LOG;
}

/*
 * Looks up the logical address from reverse trans map and check if its valid by
 * comparing the logical to physical address with the physical address.
 * Returns 0 on free, otherwise 1 if in use
 */
static void rrpc_block_map_update(struct rrpc *rrpc, struct rrpc_block *rblk)
{
        struct nvm_dev *dev = rrpc->dev;
        int offset;
        struct rrpc_addr *laddr;
        u64 bpaddr, paddr, pladdr;

        bpaddr = block_to_rel_addr(rrpc, rblk);
        for (offset = 0; offset < dev->sec_per_blk; offset++) {
                paddr = bpaddr + offset;

                pladdr = rrpc->rev_trans_map[paddr].addr;
                if (pladdr == ADDR_EMPTY)
                        continue;

                laddr = &rrpc->trans_map[pladdr];

                if (paddr == laddr->addr) {
                        laddr->rblk = rblk;
                } else {
                        set_bit(offset, rblk->invalid_pages);
                        rblk->nr_invalid_pages++;
                }
        }
}

static int rrpc_blocks_init(struct rrpc *rrpc)
{
        struct rrpc_lun *rlun;
        struct rrpc_block *rblk;
        int lun_iter, blk_iter;

        for (lun_iter = 0; lun_iter < rrpc->nr_luns; lun_iter++) {
                rlun = &rrpc->luns[lun_iter];

                for (blk_iter = 0; blk_iter < rrpc->dev->blks_per_lun;
                                                                blk_iter++) {
                        rblk = &rlun->blocks[blk_iter];
                        rrpc_block_map_update(rrpc, rblk);
                }
        }

        return 0;
}

static int rrpc_luns_configure(struct rrpc *rrpc)
{
        struct rrpc_lun *rlun;
        struct rrpc_block *rblk;
        int i;

        for (i = 0; i < rrpc->nr_luns; i++) {
                rlun = &rrpc->luns[i];

                rblk = rrpc_get_blk(rrpc, rlun, 0);
                if (!rblk)
                        goto err;
                rrpc_set_lun_cur(rlun, rblk, &rlun->cur);

                /* Emergency gc block */
                rblk = rrpc_get_blk(rrpc, rlun, 1);
                if (!rblk)
                        goto err;
                rrpc_set_lun_cur(rlun, rblk, &rlun->gc_cur);
        }

        return 0;
err:
        rrpc_put_blks(rrpc);
        return -EINVAL;
}

static struct nvm_tgt_type tt_rrpc;

static void *rrpc_init(struct nvm_dev *dev, struct gendisk *tdisk,
                                                int lun_begin, int lun_end)
{
        struct request_queue *bqueue = dev->q;
        struct request_queue *tqueue = tdisk->queue;
        struct rrpc *rrpc;
        sector_t soffset;
        int ret;

        if (!(dev->identity.dom & NVM_RSP_L2P)) {
                pr_err("nvm: rrpc: device does not support l2p (%x)\n",
                                                        dev->identity.dom);
                return ERR_PTR(-EINVAL);
        }

        rrpc = kzalloc(sizeof(struct rrpc), GFP_KERNEL);
        if (!rrpc)
                return ERR_PTR(-ENOMEM);

        rrpc->instance.tt = &tt_rrpc;
        rrpc->dev = dev;
        rrpc->disk = tdisk;

        bio_list_init(&rrpc->requeue_bios);
        spin_lock_init(&rrpc->bio_lock);
        INIT_WORK(&rrpc->ws_requeue, rrpc_requeue);

        rrpc->nr_luns = lun_end - lun_begin + 1;
        rrpc->total_blocks = (unsigned long)dev->blks_per_lun * rrpc->nr_luns;
        rrpc->nr_sects = (unsigned long long)dev->sec_per_lun * rrpc->nr_luns;

        /* simple round-robin strategy */
        atomic_set(&rrpc->next_lun, -1);

        ret = rrpc_area_init(rrpc, &soffset);
        if (ret < 0) {
                pr_err("nvm: rrpc: could not initialize area\n");
                return ERR_PTR(ret);
        }
        rrpc->soffset = soffset;

        ret = rrpc_luns_init(rrpc, lun_begin, lun_end);
        if (ret) {
                pr_err("nvm: rrpc: could not initialize luns\n");
                goto err;
        }

        rrpc->poffset = dev->sec_per_lun * lun_begin;
        rrpc->lun_offset = lun_begin;

        ret = rrpc_core_init(rrpc);
        if (ret) {
                pr_err("nvm: rrpc: could not initialize core\n");
                goto err;
        }

        ret = rrpc_map_init(rrpc);
        if (ret) {
                pr_err("nvm: rrpc: could not initialize maps\n");
                goto err;
        }

        ret = rrpc_blocks_init(rrpc);
        if (ret) {
                pr_err("nvm: rrpc: could not initialize state for blocks\n");
                goto err;
        }

        ret = rrpc_luns_configure(rrpc);
        if (ret) {
                pr_err("nvm: rrpc: not enough blocks available in LUNs.\n");
                goto err;
        }

        ret = rrpc_gc_init(rrpc);
        if (ret) {
                pr_err("nvm: rrpc: could not initialize gc\n");
                goto err;
        }

        /* inherit the size from the underlying device */
        blk_queue_logical_block_size(tqueue, queue_physical_block_size(bqueue));
        blk_queue_max_hw_sectors(tqueue, queue_max_hw_sectors(bqueue));

        pr_info("nvm: rrpc initialized with %u luns and %llu pages.\n",
                        rrpc->nr_luns, (unsigned long long)rrpc->nr_sects);

        mod_timer(&rrpc->gc_timer, jiffies + msecs_to_jiffies(10));

        return rrpc;
err:
        rrpc_free(rrpc);
        return ERR_PTR(ret);
}

/* round robin, page-based FTL, and cost-based GC */
static struct nvm_tgt_type tt_rrpc = {
        .name           = "rrpc",
        .version        = {1, 0, 0},

        .make_rq        = rrpc_make_rq,
        .capacity       = rrpc_capacity,
        .end_io         = rrpc_end_io,

        .init           = rrpc_init,
        .exit           = rrpc_exit,
};

static int __init rrpc_module_init(void)
{
        return nvm_register_tgt_type(&tt_rrpc);
}

static void rrpc_module_exit(void)
{
        nvm_unregister_tgt_type(&tt_rrpc);
}

module_init(rrpc_module_init);
module_exit(rrpc_module_exit);
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Block-Device Target for Open-Channel SSDs");