/*
 * Copyright (C) 2016 CNEX Labs
 * Initial release: Javier Gonzalez <javier@cnexlabs.com>
 *                  Matias Bjorling <matias@cnexlabs.com>
 *
 * 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.
 *
 * pblk-read.c - pblk's read path
 */

#include "pblk.h"

/*
 * There is no guarantee that the value read from cache has not been updated and
 * resides at another location in the cache. We guarantee though that if the
 * value is read from the cache, it belongs to the mapped lba. In order to
 * guarantee and order between writes and reads are ordered, a flush must be
 * issued.
 */
static int pblk_read_from_cache(struct pblk *pblk, struct bio *bio,
                                sector_t lba, struct ppa_addr ppa,
                                int bio_iter, bool advanced_bio)
{
#ifdef CONFIG_NVM_DEBUG
        /* Callers must ensure that the ppa points to a cache address */
        BUG_ON(pblk_ppa_empty(ppa));
        BUG_ON(!pblk_addr_in_cache(ppa));
#endif

        return pblk_rb_copy_to_bio(&pblk->rwb, bio, lba, ppa,
                                                bio_iter, advanced_bio);
}

static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
                                 struct bio *bio, sector_t blba,
                                 unsigned long *read_bitmap)
{
        struct pblk_sec_meta *meta_list = rqd->meta_list;
        struct ppa_addr ppas[PBLK_MAX_REQ_ADDRS];
        int nr_secs = rqd->nr_ppas;
        bool advanced_bio = false;
        int i, j = 0;

        pblk_lookup_l2p_seq(pblk, ppas, blba, nr_secs);

        for (i = 0; i < nr_secs; i++) {
                struct ppa_addr p = ppas[i];
                sector_t lba = blba + i;

retry:
                if (pblk_ppa_empty(p)) {
                        WARN_ON(test_and_set_bit(i, read_bitmap));
                        meta_list[i].lba = cpu_to_le64(ADDR_EMPTY);

                        if (unlikely(!advanced_bio)) {
                                bio_advance(bio, (i) * PBLK_EXPOSED_PAGE_SIZE);
                                advanced_bio = true;
                        }

                        goto next;
                }

                /* Try to read from write buffer. The address is later checked
                 * on the write buffer to prevent retrieving overwritten data.
                 */
                if (pblk_addr_in_cache(p)) {
                        if (!pblk_read_from_cache(pblk, bio, lba, p, i,
                                                                advanced_bio)) {
                                pblk_lookup_l2p_seq(pblk, &p, lba, 1);
                                goto retry;
                        }
                        WARN_ON(test_and_set_bit(i, read_bitmap));
                        meta_list[i].lba = cpu_to_le64(lba);
                        advanced_bio = true;
#ifdef CONFIG_NVM_DEBUG
                        atomic_long_inc(&pblk->cache_reads);
#endif
                } else {
                        /* Read from media non-cached sectors */
                        rqd->ppa_list[j++] = p;
                }

next:
                if (advanced_bio)
                        bio_advance(bio, PBLK_EXPOSED_PAGE_SIZE);
        }

        if (pblk_io_aligned(pblk, nr_secs))
                rqd->flags = pblk_set_read_mode(pblk, PBLK_READ_SEQUENTIAL);
        else
                rqd->flags = pblk_set_read_mode(pblk, PBLK_READ_RANDOM);

#ifdef CONFIG_NVM_DEBUG
        atomic_long_add(nr_secs, &pblk->inflight_reads);
#endif
}


static void pblk_read_check_seq(struct pblk *pblk, struct nvm_rq *rqd,
                                sector_t blba)
{
        struct pblk_sec_meta *meta_lba_list = rqd->meta_list;
        int nr_lbas = rqd->nr_ppas;
        int i;

        for (i = 0; i < nr_lbas; i++) {
                u64 lba = le64_to_cpu(meta_lba_list[i].lba);

                if (lba == ADDR_EMPTY)
                        continue;

                if (lba != blba + i) {
#ifdef CONFIG_NVM_DEBUG
                        struct ppa_addr *p;

                        p = (nr_lbas == 1) ? &rqd->ppa_list[i] : &rqd->ppa_addr;
                        print_ppa(&pblk->dev->geo, p, "seq", i);
#endif
                        pr_err("pblk: corrupted read LBA (%llu/%llu)\n",
                                                        lba, (u64)blba + i);
                        WARN_ON(1);
                }
        }
}

/*
 * There can be holes in the lba list.
 */
static void pblk_read_check_rand(struct pblk *pblk, struct nvm_rq *rqd,
                                 u64 *lba_list, int nr_lbas)
{
        struct pblk_sec_meta *meta_lba_list = rqd->meta_list;
        int i, j;

        for (i = 0, j = 0; i < nr_lbas; i++) {
                u64 lba = lba_list[i];
                u64 meta_lba;

                if (lba == ADDR_EMPTY)
                        continue;

                meta_lba = le64_to_cpu(meta_lba_list[j].lba);

                if (lba != meta_lba) {
#ifdef CONFIG_NVM_DEBUG
                        struct ppa_addr *p;
                        int nr_ppas = rqd->nr_ppas;

                        p = (nr_ppas == 1) ? &rqd->ppa_list[j] : &rqd->ppa_addr;
                        print_ppa(&pblk->dev->geo, p, "seq", j);
#endif
                        pr_err("pblk: corrupted read LBA (%llu/%llu)\n",
                                                                lba, meta_lba);
                        WARN_ON(1);
                }

                j++;
        }

        WARN_ONCE(j != rqd->nr_ppas, "pblk: corrupted random request\n");
}

static void pblk_read_put_rqd_kref(struct pblk *pblk, struct nvm_rq *rqd)
{
        struct ppa_addr *ppa_list;
        int i;

        ppa_list = (rqd->nr_ppas > 1) ? rqd->ppa_list : &rqd->ppa_addr;

        for (i = 0; i < rqd->nr_ppas; i++) {
                struct ppa_addr ppa = ppa_list[i];
                struct pblk_line *line;

                line = &pblk->lines[pblk_ppa_to_line(ppa)];
                kref_put(&line->ref, pblk_line_put_wq);
        }
}

static void pblk_end_user_read(struct bio *bio)
{
#ifdef CONFIG_NVM_DEBUG
        WARN_ONCE(bio->bi_status, "pblk: corrupted read bio\n");
#endif
        bio_endio(bio);
}

static void __pblk_end_io_read(struct pblk *pblk, struct nvm_rq *rqd,
                               bool put_line)
{
        struct nvm_tgt_dev *dev = pblk->dev;
        struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd);
        struct bio *int_bio = rqd->bio;
        unsigned long start_time = r_ctx->start_time;

        generic_end_io_acct(dev->q, REQ_OP_READ, &pblk->disk->part0, start_time);

        if (rqd->error)
                pblk_log_read_err(pblk, rqd);

        pblk_read_check_seq(pblk, rqd, r_ctx->lba);

        if (int_bio)
                bio_put(int_bio);

        if (put_line)
                pblk_read_put_rqd_kref(pblk, rqd);

#ifdef CONFIG_NVM_DEBUG
        atomic_long_add(rqd->nr_ppas, &pblk->sync_reads);
        atomic_long_sub(rqd->nr_ppas, &pblk->inflight_reads);
#endif

        pblk_free_rqd(pblk, rqd, PBLK_READ);
        atomic_dec(&pblk->inflight_io);
}

static void pblk_end_io_read(struct nvm_rq *rqd)
{
        struct pblk *pblk = rqd->private;
        struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd);
        struct bio *bio = (struct bio *)r_ctx->private;

        pblk_end_user_read(bio);
        __pblk_end_io_read(pblk, rqd, true);
}

static int pblk_partial_read(struct pblk *pblk, struct nvm_rq *rqd,
                             struct bio *orig_bio, unsigned int bio_init_idx,
                             unsigned long *read_bitmap)
{
        struct pblk_sec_meta *meta_list = rqd->meta_list;
        struct bio *new_bio;
        struct bio_vec src_bv, dst_bv;
        void *ppa_ptr = NULL;
        void *src_p, *dst_p;
        dma_addr_t dma_ppa_list = 0;
        __le64 *lba_list_mem, *lba_list_media;
        int nr_secs = rqd->nr_ppas;
        int nr_holes = nr_secs - bitmap_weight(read_bitmap, nr_secs);
        int i, ret, hole;

        /* Re-use allocated memory for intermediate lbas */
        lba_list_mem = (((void *)rqd->ppa_list) + pblk_dma_ppa_size);
        lba_list_media = (((void *)rqd->ppa_list) + 2 * pblk_dma_ppa_size);

        new_bio = bio_alloc(GFP_KERNEL, nr_holes);

        if (pblk_bio_add_pages(pblk, new_bio, GFP_KERNEL, nr_holes))
                goto fail_add_pages;

        if (nr_holes != new_bio->bi_vcnt) {
                pr_err("pblk: malformed bio\n");
                goto fail;
        }

        for (i = 0; i < nr_secs; i++)
                lba_list_mem[i] = meta_list[i].lba;

        new_bio->bi_iter.bi_sector = 0; /* internal bio */
        bio_set_op_attrs(new_bio, REQ_OP_READ, 0);

        rqd->bio = new_bio;
        rqd->nr_ppas = nr_holes;
        rqd->flags = pblk_set_read_mode(pblk, PBLK_READ_RANDOM);

        if (unlikely(nr_holes == 1)) {
                ppa_ptr = rqd->ppa_list;
                dma_ppa_list = rqd->dma_ppa_list;
                rqd->ppa_addr = rqd->ppa_list[0];
        }

        ret = pblk_submit_io_sync(pblk, rqd);
        if (ret) {
                bio_put(rqd->bio);
                pr_err("pblk: sync read IO submission failed\n");
                goto fail;
        }

        if (rqd->error) {
                atomic_long_inc(&pblk->read_failed);
#ifdef CONFIG_NVM_DEBUG
                pblk_print_failed_rqd(pblk, rqd, rqd->error);
#endif
        }

        if (unlikely(nr_holes == 1)) {
                struct ppa_addr ppa;

                ppa = rqd->ppa_addr;
                rqd->ppa_list = ppa_ptr;
                rqd->dma_ppa_list = dma_ppa_list;
                rqd->ppa_list[0] = ppa;
        }

        for (i = 0; i < nr_secs; i++) {
                lba_list_media[i] = meta_list[i].lba;
                meta_list[i].lba = lba_list_mem[i];
        }

        /* Fill the holes in the original bio */
        i = 0;
        hole = find_first_zero_bit(read_bitmap, nr_secs);
        do {
                int line_id = pblk_ppa_to_line(rqd->ppa_list[i]);
                struct pblk_line *line = &pblk->lines[line_id];

                kref_put(&line->ref, pblk_line_put);

                meta_list[hole].lba = lba_list_media[i];

                src_bv = new_bio->bi_io_vec[i++];
                dst_bv = orig_bio->bi_io_vec[bio_init_idx + hole];

                src_p = kmap_atomic(src_bv.bv_page);
                dst_p = kmap_atomic(dst_bv.bv_page);

                memcpy(dst_p + dst_bv.bv_offset,
                        src_p + src_bv.bv_offset,
                        PBLK_EXPOSED_PAGE_SIZE);

                kunmap_atomic(src_p);
                kunmap_atomic(dst_p);

                mempool_free(src_bv.bv_page, &pblk->page_bio_pool);

                hole = find_next_zero_bit(read_bitmap, nr_secs, hole + 1);
        } while (hole < nr_secs);

        bio_put(new_bio);

        /* restore original request */
        rqd->bio = NULL;
        rqd->nr_ppas = nr_secs;

        __pblk_end_io_read(pblk, rqd, false);
        return NVM_IO_DONE;

fail:
        /* Free allocated pages in new bio */
        pblk_bio_free_pages(pblk, new_bio, 0, new_bio->bi_vcnt);
fail_add_pages:
        pr_err("pblk: failed to perform partial read\n");
        __pblk_end_io_read(pblk, rqd, false);
        return NVM_IO_ERR;
}

static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd, struct bio *bio,
                         sector_t lba, unsigned long *read_bitmap)
{
        struct pblk_sec_meta *meta_list = rqd->meta_list;
        struct ppa_addr ppa;

        pblk_lookup_l2p_seq(pblk, &ppa, lba, 1);

#ifdef CONFIG_NVM_DEBUG
        atomic_long_inc(&pblk->inflight_reads);
#endif

retry:
        if (pblk_ppa_empty(ppa)) {
                WARN_ON(test_and_set_bit(0, read_bitmap));
                meta_list[0].lba = cpu_to_le64(ADDR_EMPTY);
                return;
        }

        /* Try to read from write buffer. The address is later checked on the
         * write buffer to prevent retrieving overwritten data.
         */
        if (pblk_addr_in_cache(ppa)) {
                if (!pblk_read_from_cache(pblk, bio, lba, ppa, 0, 1)) {
                        pblk_lookup_l2p_seq(pblk, &ppa, lba, 1);
                        goto retry;
                }

                WARN_ON(test_and_set_bit(0, read_bitmap));
                meta_list[0].lba = cpu_to_le64(lba);

#ifdef CONFIG_NVM_DEBUG
                atomic_long_inc(&pblk->cache_reads);
#endif
        } else {
                rqd->ppa_addr = ppa;
        }

        rqd->flags = pblk_set_read_mode(pblk, PBLK_READ_RANDOM);
}

int pblk_submit_read(struct pblk *pblk, struct bio *bio)
{
        struct nvm_tgt_dev *dev = pblk->dev;
        struct request_queue *q = dev->q;
        sector_t blba = pblk_get_lba(bio);
        unsigned int nr_secs = pblk_get_secs(bio);
        struct pblk_g_ctx *r_ctx;
        struct nvm_rq *rqd;
        unsigned int bio_init_idx;
        unsigned long read_bitmap; /* Max 64 ppas per request */
        int ret = NVM_IO_ERR;

        /* logic error: lba out-of-bounds. Ignore read request */
        if (blba >= pblk->rl.nr_secs || nr_secs > PBLK_MAX_REQ_ADDRS) {
                WARN(1, "pblk: read lba out of bounds (lba:%llu, nr:%d)\n",
                                        (unsigned long long)blba, nr_secs);
                return NVM_IO_ERR;
        }

        generic_start_io_acct(q, REQ_OP_READ, bio_sectors(bio),
                              &pblk->disk->part0);

        bitmap_zero(&read_bitmap, nr_secs);

        rqd = pblk_alloc_rqd(pblk, PBLK_READ);

        rqd->opcode = NVM_OP_PREAD;
        rqd->nr_ppas = nr_secs;
        rqd->bio = NULL; /* cloned bio if needed */
        rqd->private = pblk;
        rqd->end_io = pblk_end_io_read;

        r_ctx = nvm_rq_to_pdu(rqd);
        r_ctx->start_time = jiffies;
        r_ctx->lba = blba;
        r_ctx->private = bio; /* original bio */

        /* Save the index for this bio's start. This is needed in case
         * we need to fill a partial read.
         */
        bio_init_idx = pblk_get_bi_idx(bio);

        rqd->meta_list = nvm_dev_dma_alloc(dev->parent, GFP_KERNEL,
                                                        &rqd->dma_meta_list);
        if (!rqd->meta_list) {
                pr_err("pblk: not able to allocate ppa list\n");
                goto fail_rqd_free;
        }

        if (nr_secs > 1) {
                rqd->ppa_list = rqd->meta_list + pblk_dma_meta_size;
                rqd->dma_ppa_list = rqd->dma_meta_list + pblk_dma_meta_size;

                pblk_read_ppalist_rq(pblk, rqd, bio, blba, &read_bitmap);
        } else {
                pblk_read_rq(pblk, rqd, bio, blba, &read_bitmap);
        }

        if (bitmap_full(&read_bitmap, nr_secs)) {
                atomic_inc(&pblk->inflight_io);
                __pblk_end_io_read(pblk, rqd, false);
                return NVM_IO_DONE;
        }

        /* All sectors are to be read from the device */
        if (bitmap_empty(&read_bitmap, rqd->nr_ppas)) {
                struct bio *int_bio = NULL;

                /* Clone read bio to deal with read errors internally */
                int_bio = bio_clone_fast(bio, GFP_KERNEL, &pblk_bio_set);
                if (!int_bio) {
                        pr_err("pblk: could not clone read bio\n");
                        goto fail_end_io;
                }

                rqd->bio = int_bio;

                if (pblk_submit_io(pblk, rqd)) {
                        pr_err("pblk: read IO submission failed\n");
                        ret = NVM_IO_ERR;
                        goto fail_end_io;
                }

                return NVM_IO_OK;
        }

        /* The read bio request could be partially filled by the write buffer,
         * but there are some holes that need to be read from the drive.
         */
        return pblk_partial_read(pblk, rqd, bio, bio_init_idx, &read_bitmap);

fail_rqd_free:
        pblk_free_rqd(pblk, rqd, PBLK_READ);
        return ret;
fail_end_io:
        __pblk_end_io_read(pblk, rqd, false);
        return ret;
}

static int read_ppalist_rq_gc(struct pblk *pblk, struct nvm_rq *rqd,
                              struct pblk_line *line, u64 *lba_list,
                              u64 *paddr_list_gc, unsigned int nr_secs)
{
        struct ppa_addr ppa_list_l2p[PBLK_MAX_REQ_ADDRS];
        struct ppa_addr ppa_gc;
        int valid_secs = 0;
        int i;

        pblk_lookup_l2p_rand(pblk, ppa_list_l2p, lba_list, nr_secs);

        for (i = 0; i < nr_secs; i++) {
                if (lba_list[i] == ADDR_EMPTY)
                        continue;

                ppa_gc = addr_to_gen_ppa(pblk, paddr_list_gc[i], line->id);
                if (!pblk_ppa_comp(ppa_list_l2p[i], ppa_gc)) {
                        paddr_list_gc[i] = lba_list[i] = ADDR_EMPTY;
                        continue;
                }

                rqd->ppa_list[valid_secs++] = ppa_list_l2p[i];
        }

#ifdef CONFIG_NVM_DEBUG
        atomic_long_add(valid_secs, &pblk->inflight_reads);
#endif

        return valid_secs;
}

static int read_rq_gc(struct pblk *pblk, struct nvm_rq *rqd,
                      struct pblk_line *line, sector_t lba,
                      u64 paddr_gc)
{
        struct ppa_addr ppa_l2p, ppa_gc;
        int valid_secs = 0;

        if (lba == ADDR_EMPTY)
                goto out;

        /* logic error: lba out-of-bounds */
        if (lba >= pblk->rl.nr_secs) {
                WARN(1, "pblk: read lba out of bounds\n");
                goto out;
        }

        spin_lock(&pblk->trans_lock);
        ppa_l2p = pblk_trans_map_get(pblk, lba);
        spin_unlock(&pblk->trans_lock);

        ppa_gc = addr_to_gen_ppa(pblk, paddr_gc, line->id);
        if (!pblk_ppa_comp(ppa_l2p, ppa_gc))
                goto out;

        rqd->ppa_addr = ppa_l2p;
        valid_secs = 1;

#ifdef CONFIG_NVM_DEBUG
        atomic_long_inc(&pblk->inflight_reads);
#endif

out:
        return valid_secs;
}

int pblk_submit_read_gc(struct pblk *pblk, struct pblk_gc_rq *gc_rq)
{
        struct nvm_tgt_dev *dev = pblk->dev;
        struct nvm_geo *geo = &dev->geo;
        struct bio *bio;
        struct nvm_rq rqd;
        int data_len;
        int ret = NVM_IO_OK;

        memset(&rqd, 0, sizeof(struct nvm_rq));

        rqd.meta_list = nvm_dev_dma_alloc(dev->parent, GFP_KERNEL,
                                                        &rqd.dma_meta_list);
        if (!rqd.meta_list)
                return -ENOMEM;

        if (gc_rq->nr_secs > 1) {
                rqd.ppa_list = rqd.meta_list + pblk_dma_meta_size;
                rqd.dma_ppa_list = rqd.dma_meta_list + pblk_dma_meta_size;

                gc_rq->secs_to_gc = read_ppalist_rq_gc(pblk, &rqd, gc_rq->line,
                                                        gc_rq->lba_list,
                                                        gc_rq->paddr_list,
                                                        gc_rq->nr_secs);
                if (gc_rq->secs_to_gc == 1)
                        rqd.ppa_addr = rqd.ppa_list[0];
        } else {
                gc_rq->secs_to_gc = read_rq_gc(pblk, &rqd, gc_rq->line,
                                                        gc_rq->lba_list[0],
                                                        gc_rq->paddr_list[0]);
        }

        if (!(gc_rq->secs_to_gc))
                goto out;

        data_len = (gc_rq->secs_to_gc) * geo->csecs;
        bio = pblk_bio_map_addr(pblk, gc_rq->data, gc_rq->secs_to_gc, data_len,
                                                PBLK_VMALLOC_META, GFP_KERNEL);
        if (IS_ERR(bio)) {
                pr_err("pblk: could not allocate GC bio (%lu)\n", PTR_ERR(bio));
                goto err_free_dma;
        }

        bio->bi_iter.bi_sector = 0; /* internal bio */
        bio_set_op_attrs(bio, REQ_OP_READ, 0);

        rqd.opcode = NVM_OP_PREAD;
        rqd.nr_ppas = gc_rq->secs_to_gc;
        rqd.flags = pblk_set_read_mode(pblk, PBLK_READ_RANDOM);
        rqd.bio = bio;

        if (pblk_submit_io_sync(pblk, &rqd)) {
                ret = -EIO;
                pr_err("pblk: GC read request failed\n");
                goto err_free_bio;
        }

        pblk_read_check_rand(pblk, &rqd, gc_rq->lba_list, gc_rq->nr_secs);

        atomic_dec(&pblk->inflight_io);

        if (rqd.error) {
                atomic_long_inc(&pblk->read_failed_gc);
#ifdef CONFIG_NVM_DEBUG
                pblk_print_failed_rqd(pblk, &rqd, rqd.error);
#endif
        }

#ifdef CONFIG_NVM_DEBUG
        atomic_long_add(gc_rq->secs_to_gc, &pblk->sync_reads);
        atomic_long_add(gc_rq->secs_to_gc, &pblk->recov_gc_reads);
        atomic_long_sub(gc_rq->secs_to_gc, &pblk->inflight_reads);
#endif

out:
        nvm_dev_dma_free(dev->parent, rqd.meta_list, rqd.dma_meta_list);
        return ret;

err_free_bio:
        bio_put(bio);
err_free_dma:
        nvm_dev_dma_free(dev->parent, rqd.meta_list, rqd.dma_meta_list);
        return ret;
}