/*
   * 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,
  				 unsigned long *read_bitmap)
  {
  	struct bio *bio = rqd->bio;
  	struct ppa_addr ppas[PBLK_MAX_REQ_ADDRS];
  	sector_t blba = pblk_get_lba(bio);
  	int nr_secs = rqd->nr_ppas;

  	bool advanced_bio = false;

  	int i, j = 0;
  
  	/* logic error: lba out-of-bounds. Ignore read request */

  	if (blba + nr_secs >= pblk->rl.nr_secs) {
  		WARN(1, "pblk: read lbas out of bounds
  ");

  		return;
  	}
  
  	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));

  
  			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));

  			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 int pblk_submit_read_io(struct pblk *pblk, struct nvm_rq *rqd)
  {
  	int err;

  	err = pblk_submit_io(pblk, rqd);
  	if (err)
  		return NVM_IO_ERR;
  
  	return NVM_IO_OK;
  }
  
  static void pblk_end_io_read(struct nvm_rq *rqd)
  {
  	struct pblk *pblk = rqd->private;
  	struct nvm_tgt_dev *dev = pblk->dev;

  	struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd);

  	struct bio *bio = rqd->bio;
  
  	if (rqd->error)
  		pblk_log_read_err(pblk, rqd);
  #ifdef CONFIG_NVM_DEBUG
  	else

  		WARN_ONCE(bio->bi_status, "pblk: corrupted read error
  ");

  #endif

  	nvm_dev_dma_free(dev->parent, rqd->meta_list, rqd->dma_meta_list);

  
  	bio_put(bio);

  	if (r_ctx->private) {
  		struct bio *orig_bio = r_ctx->private;

  #ifdef CONFIG_NVM_DEBUG

  		WARN_ONCE(orig_bio->bi_status, "pblk: corrupted read bio
  ");

  #endif

  		bio_endio(orig_bio);
  		bio_put(orig_bio);

  	}
  
  #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, READ);

  	atomic_dec(&pblk->inflight_io);

  }
  
  static int pblk_fill_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
  				      unsigned int bio_init_idx,
  				      unsigned long *read_bitmap)
  {
  	struct bio *new_bio, *bio = rqd->bio;
  	struct bio_vec src_bv, dst_bv;
  	void *ppa_ptr = NULL;
  	void *src_p, *dst_p;
  	dma_addr_t dma_ppa_list = 0;
  	int nr_secs = rqd->nr_ppas;
  	int nr_holes = nr_secs - bitmap_weight(read_bitmap, nr_secs);
  	int i, ret, hole;
  	DECLARE_COMPLETION_ONSTACK(wait);
  
  	new_bio = bio_alloc(GFP_KERNEL, nr_holes);
  	if (!new_bio) {
  		pr_err("pblk: could not alloc read bio
  ");
  		return NVM_IO_ERR;
  	}
  
  	if (pblk_bio_add_pages(pblk, new_bio, GFP_KERNEL, nr_holes))
  		goto err;
  
  	if (nr_holes != new_bio->bi_vcnt) {
  		pr_err("pblk: malformed bio
  ");
  		goto err;
  	}
  
  	new_bio->bi_iter.bi_sector = 0; /* internal bio */
  	bio_set_op_attrs(new_bio, REQ_OP_READ, 0);
  	new_bio->bi_private = &wait;
  	new_bio->bi_end_io = pblk_end_bio_sync;
  
  	rqd->bio = new_bio;
  	rqd->nr_ppas = nr_holes;

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

  	rqd->end_io = NULL;
  
  	if (unlikely(nr_secs > 1 && 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_read_io(pblk, rqd);
  	if (ret) {
  		bio_put(rqd->bio);
  		pr_err("pblk: read IO submission failed
  ");
  		goto err;
  	}
  
  	if (!wait_for_completion_io_timeout(&wait,
  				msecs_to_jiffies(PBLK_COMMAND_TIMEOUT_MS))) {
  		pr_err("pblk: partial read I/O timed out
  ");
  	}
  
  	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_secs > 1 && nr_holes == 1)) {
  		rqd->ppa_list = ppa_ptr;
  		rqd->dma_ppa_list = dma_ppa_list;
  	}
  
  	/* Fill the holes in the original bio */
  	i = 0;
  	hole = find_first_zero_bit(read_bitmap, nr_secs);
  	do {
  		src_bv = new_bio->bi_io_vec[i++];
  		dst_bv = 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);
  
  	/* Complete the original bio and associated request */
  	rqd->bio = bio;
  	rqd->nr_ppas = nr_secs;
  	rqd->private = pblk;
  
  	bio_endio(bio);
  	pblk_end_io_read(rqd);
  	return NVM_IO_OK;
  
  err:
  	/* Free allocated pages in new bio */
  	pblk_bio_free_pages(pblk, bio, 0, new_bio->bi_vcnt);
  	rqd->private = pblk;
  	pblk_end_io_read(rqd);
  	return NVM_IO_ERR;
  }
  
  static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd,
  			 unsigned long *read_bitmap)
  {
  	struct bio *bio = rqd->bio;
  	struct ppa_addr ppa;
  	sector_t lba = pblk_get_lba(bio);
  
  	/* logic error: lba out-of-bounds. Ignore read request */

  	if (lba >= pblk->rl.nr_secs) {
  		WARN(1, "pblk: read lba out of bounds
  ");

  		return;
  	}
  
  	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));
  		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));

  #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;

  	unsigned int nr_secs = pblk_get_secs(bio);

  	struct nvm_rq *rqd;
  	unsigned long read_bitmap; /* Max 64 ppas per request */
  	unsigned int bio_init_idx;
  	int ret = NVM_IO_ERR;
  
  	if (nr_secs > PBLK_MAX_REQ_ADDRS)
  		return NVM_IO_ERR;
  
  	bitmap_zero(&read_bitmap, nr_secs);
  
  	rqd = pblk_alloc_rqd(pblk, READ);
  	if (IS_ERR(rqd)) {
  		pr_err_ratelimited("pblk: not able to alloc rqd");
  		return NVM_IO_ERR;
  	}
  
  	rqd->opcode = NVM_OP_PREAD;
  	rqd->bio = bio;
  	rqd->nr_ppas = nr_secs;
  	rqd->private = pblk;
  	rqd->end_io = pblk_end_io_read;
  
  	/* 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
  ");
  		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, &read_bitmap);
  	} else {
  		pblk_read_rq(pblk, rqd, &read_bitmap);
  	}
  
  	bio_get(bio);
  	if (bitmap_full(&read_bitmap, nr_secs)) {
  		bio_endio(bio);

  		atomic_inc(&pblk->inflight_io);

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

  		struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd);

  
  		/* 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
  ");
  			return NVM_IO_ERR;
  		}
  
  		rqd->bio = int_bio;

  		r_ctx->private = bio;

  
  		ret = pblk_submit_read_io(pblk, rqd);
  		if (ret) {
  			pr_err("pblk: read IO submission failed
  ");
  			if (int_bio)
  				bio_put(int_bio);
  			return ret;
  		}
  
  		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.
  	 */
  	ret = pblk_fill_partial_read_bio(pblk, rqd, bio_init_idx, &read_bitmap);
  	if (ret) {
  		pr_err("pblk: failed to perform partial read
  ");
  		return ret;
  	}
  
  	return NVM_IO_OK;
  
  fail_rqd_free:
  	pblk_free_rqd(pblk, rqd, READ);
  	return ret;
  }
  
  static int read_ppalist_rq_gc(struct pblk *pblk, struct nvm_rq *rqd,
  			      struct pblk_line *line, u64 *lba_list,
  			      unsigned int nr_secs)
  {
  	struct ppa_addr ppas[PBLK_MAX_REQ_ADDRS];
  	int valid_secs = 0;
  	int i;
  
  	pblk_lookup_l2p_rand(pblk, ppas, lba_list, nr_secs);
  
  	for (i = 0; i < nr_secs; i++) {
  		if (pblk_addr_in_cache(ppas[i]) || ppas[i].g.blk != line->id ||
  						pblk_ppa_empty(ppas[i])) {
  			lba_list[i] = ADDR_EMPTY;
  			continue;
  		}
  
  		rqd->ppa_list[valid_secs++] = ppas[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)
  {
  	struct ppa_addr ppa;
  	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
  ");

  		goto out;
  	}

  	spin_lock(&pblk->trans_lock);
  	ppa = pblk_trans_map_get(pblk, lba);
  	spin_unlock(&pblk->trans_lock);
  
  	/* Ignore updated values until the moment */
  	if (pblk_addr_in_cache(ppa) || ppa.g.blk != line->id ||
  							pblk_ppa_empty(ppa))
  		goto out;
  
  	rqd->ppa_addr = ppa;
  	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, u64 *lba_list, void *data,
  			unsigned int nr_secs, unsigned int *secs_to_gc,
  			struct pblk_line *line)
  {
  	struct nvm_tgt_dev *dev = pblk->dev;
  	struct nvm_geo *geo = &dev->geo;

  	struct bio *bio;
  	struct nvm_rq rqd;
  	int ret, data_len;
  	DECLARE_COMPLETION_ONSTACK(wait);
  
  	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 NVM_IO_ERR;

  	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;

  
  		*secs_to_gc = read_ppalist_rq_gc(pblk, &rqd, line, lba_list,
  								nr_secs);

  		if (*secs_to_gc == 1)
  			rqd.ppa_addr = rqd.ppa_list[0];

  	} else {
  		*secs_to_gc = read_rq_gc(pblk, &rqd, line, lba_list[0]);
  	}
  
  	if (!(*secs_to_gc))
  		goto out;
  
  	data_len = (*secs_to_gc) * geo->sec_size;

  	bio = pblk_bio_map_addr(pblk, data, *secs_to_gc, data_len,

  						PBLK_VMALLOC_META, GFP_KERNEL);

  	if (IS_ERR(bio)) {
  		pr_err("pblk: could not allocate GC bio (%lu)
  ", 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.end_io = pblk_end_io_sync;
  	rqd.private = &wait;
  	rqd.nr_ppas = *secs_to_gc;

  	rqd.flags = pblk_set_read_mode(pblk, PBLK_READ_RANDOM);

  	rqd.bio = bio;
  
  	ret = pblk_submit_read_io(pblk, &rqd);
  	if (ret) {
  		bio_endio(bio);
  		pr_err("pblk: GC read request failed
  ");

  		goto err_free_bio;

  	}
  
  	if (!wait_for_completion_io_timeout(&wait,
  				msecs_to_jiffies(PBLK_COMMAND_TIMEOUT_MS))) {
  		pr_err("pblk: GC read I/O timed out
  ");
  	}

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

  	bio_put(bio);

  out:

  	nvm_dev_dma_free(dev->parent, rqd.meta_list, rqd.dma_meta_list);

  	return NVM_IO_OK;

  err_free_bio:
  	bio_put(bio);

  err_free_dma:

  	nvm_dev_dma_free(dev->parent, rqd.meta_list, rqd.dma_meta_list);

  	return NVM_IO_ERR;
  }