/*
   * Functions related to generic helpers functions
   */
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/bio.h>
  #include <linux/blkdev.h>
  #include <linux/scatterlist.h>
  
  #include "blk.h"

  static struct bio *next_bio(struct bio *bio, unsigned int nr_pages,

  		gfp_t gfp)

  {

  	struct bio *new = bio_alloc(gfp, nr_pages);
  
  	if (bio) {
  		bio_chain(bio, new);

  		submit_bio(bio);

  	}

  	return new;

  }

  int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,

  		sector_t nr_sects, gfp_t gfp_mask, int flags,

  		struct bio **biop)

  {

  	struct request_queue *q = bdev_get_queue(bdev);

  	struct bio *bio = *biop;

  	unsigned int granularity;

  	unsigned int op;

  	int alignment;

  	sector_t bs_mask;

  
  	if (!q)
  		return -ENXIO;

  
  	if (flags & BLKDEV_DISCARD_SECURE) {

  		if (flags & BLKDEV_DISCARD_ZERO)
  			return -EOPNOTSUPP;

  		if (!blk_queue_secure_erase(q))
  			return -EOPNOTSUPP;
  		op = REQ_OP_SECURE_ERASE;
  	} else {
  		if (!blk_queue_discard(q))
  			return -EOPNOTSUPP;

  		if ((flags & BLKDEV_DISCARD_ZERO) &&
  		    !q->limits.discard_zeroes_data)
  			return -EOPNOTSUPP;

  		op = REQ_OP_DISCARD;
  	}

  	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
  	if ((sector | nr_sects) & bs_mask)
  		return -EINVAL;

  	/* Zero-sector (unknown) and one-sector granularities are the same.  */
  	granularity = max(q->limits.discard_granularity >> 9, 1U);
  	alignment = (bdev_discard_alignment(bdev) >> 9) % granularity;

  	while (nr_sects) {

  		unsigned int req_sects;

  		sector_t end_sect, tmp;

  		/* Make sure bi_size doesn't overflow */
  		req_sects = min_t(sector_t, nr_sects, UINT_MAX >> 9);

  		/**

  		 * If splitting a request, and the next starting sector would be
  		 * misaligned, stop the discard at the previous aligned sector.
  		 */

  		end_sect = sector + req_sects;

  		tmp = end_sect;
  		if (req_sects < nr_sects &&
  		    sector_div(tmp, granularity) != alignment) {
  			end_sect = end_sect - alignment;
  			sector_div(end_sect, granularity);
  			end_sect = end_sect * granularity + alignment;
  			req_sects = end_sect - sector;
  		}

  		bio = next_bio(bio, 0, gfp_mask);

  		bio->bi_iter.bi_sector = sector;

  		bio->bi_bdev = bdev;

  		bio_set_op_attrs(bio, op, 0);

  		bio->bi_iter.bi_size = req_sects << 9;

  		nr_sects -= req_sects;
  		sector = end_sect;

  		/*
  		 * We can loop for a long time in here, if someone does
  		 * full device discards (like mkfs). Be nice and allow
  		 * us to schedule out to avoid softlocking if preempt
  		 * is disabled.
  		 */
  		cond_resched();

  	}

  
  	*biop = bio;
  	return 0;
  }
  EXPORT_SYMBOL(__blkdev_issue_discard);
  
  /**
   * blkdev_issue_discard - queue a discard
   * @bdev:	blockdev to issue discard for
   * @sector:	start sector
   * @nr_sects:	number of sectors to discard
   * @gfp_mask:	memory allocation flags (for bio_alloc)
   * @flags:	BLKDEV_IFL_* flags to control behaviour
   *
   * Description:
   *    Issue a discard request for the sectors in question.
   */
  int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
  		sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
  {

  	struct bio *bio = NULL;
  	struct blk_plug plug;
  	int ret;

  	blk_start_plug(&plug);

  	ret = __blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, flags,

  			&bio);

  	if (!ret && bio) {

  		ret = submit_bio_wait(bio);

  		if (ret == -EOPNOTSUPP && !(flags & BLKDEV_DISCARD_ZERO))

  			ret = 0;

  		bio_put(bio);

  	}

  	blk_finish_plug(&plug);

  	return ret;

  }
  EXPORT_SYMBOL(blkdev_issue_discard);

  /**

   * __blkdev_issue_write_same - generate number of bios with same page

   * @bdev:	target blockdev
   * @sector:	start sector
   * @nr_sects:	number of sectors to write
   * @gfp_mask:	memory allocation flags (for bio_alloc)
   * @page:	page containing data to write

   * @biop:	pointer to anchor bio

   *
   * Description:

   *  Generate and issue number of bios(REQ_OP_WRITE_SAME) with same page.

   */

  static int __blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
  		sector_t nr_sects, gfp_t gfp_mask, struct page *page,
  		struct bio **biop)

  {

  	struct request_queue *q = bdev_get_queue(bdev);
  	unsigned int max_write_same_sectors;

  	struct bio *bio = *biop;

  	sector_t bs_mask;

  
  	if (!q)
  		return -ENXIO;

  	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
  	if ((sector | nr_sects) & bs_mask)
  		return -EINVAL;

  	if (!bdev_write_same(bdev))
  		return -EOPNOTSUPP;

  	/* Ensure that max_write_same_sectors doesn't overflow bi_size */
  	max_write_same_sectors = UINT_MAX >> 9;

  	while (nr_sects) {

  		bio = next_bio(bio, 1, gfp_mask);

  		bio->bi_iter.bi_sector = sector;

  		bio->bi_bdev = bdev;

  		bio->bi_vcnt = 1;
  		bio->bi_io_vec->bv_page = page;
  		bio->bi_io_vec->bv_offset = 0;
  		bio->bi_io_vec->bv_len = bdev_logical_block_size(bdev);

  		bio_set_op_attrs(bio, REQ_OP_WRITE_SAME, 0);

  
  		if (nr_sects > max_write_same_sectors) {

  			bio->bi_iter.bi_size = max_write_same_sectors << 9;

  			nr_sects -= max_write_same_sectors;
  			sector += max_write_same_sectors;
  		} else {

  			bio->bi_iter.bi_size = nr_sects << 9;

  			nr_sects = 0;
  		}

  		cond_resched();

  	}

  	*biop = bio;
  	return 0;
  }
  
  /**
   * blkdev_issue_write_same - queue a write same operation
   * @bdev:	target blockdev
   * @sector:	start sector
   * @nr_sects:	number of sectors to write
   * @gfp_mask:	memory allocation flags (for bio_alloc)
   * @page:	page containing data
   *
   * Description:
   *    Issue a write same request for the sectors in question.
   */
  int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
  				sector_t nr_sects, gfp_t gfp_mask,
  				struct page *page)
  {
  	struct bio *bio = NULL;
  	struct blk_plug plug;
  	int ret;
  
  	blk_start_plug(&plug);
  	ret = __blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask, page,
  			&bio);
  	if (ret == 0 && bio) {

  		ret = submit_bio_wait(bio);

  		bio_put(bio);
  	}

  	blk_finish_plug(&plug);

  	return ret;

  }
  EXPORT_SYMBOL(blkdev_issue_write_same);
  
  /**

   * __blkdev_issue_write_zeroes - generate number of bios with WRITE ZEROES
   * @bdev:	blockdev to issue
   * @sector:	start sector
   * @nr_sects:	number of sectors to write
   * @gfp_mask:	memory allocation flags (for bio_alloc)
   * @biop:	pointer to anchor bio
   *
   * Description:
   *  Generate and issue number of bios(REQ_OP_WRITE_ZEROES) with zerofiled pages.
   */
  static int __blkdev_issue_write_zeroes(struct block_device *bdev,
  		sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
  		struct bio **biop)
  {
  	struct bio *bio = *biop;
  	unsigned int max_write_zeroes_sectors;
  	struct request_queue *q = bdev_get_queue(bdev);
  
  	if (!q)
  		return -ENXIO;
  
  	/* Ensure that max_write_zeroes_sectors doesn't overflow bi_size */
  	max_write_zeroes_sectors = bdev_write_zeroes_sectors(bdev);
  
  	if (max_write_zeroes_sectors == 0)
  		return -EOPNOTSUPP;
  
  	while (nr_sects) {
  		bio = next_bio(bio, 0, gfp_mask);
  		bio->bi_iter.bi_sector = sector;
  		bio->bi_bdev = bdev;
  		bio_set_op_attrs(bio, REQ_OP_WRITE_ZEROES, 0);
  
  		if (nr_sects > max_write_zeroes_sectors) {
  			bio->bi_iter.bi_size = max_write_zeroes_sectors << 9;
  			nr_sects -= max_write_zeroes_sectors;
  			sector += max_write_zeroes_sectors;
  		} else {
  			bio->bi_iter.bi_size = nr_sects << 9;
  			nr_sects = 0;
  		}
  		cond_resched();
  	}
  
  	*biop = bio;
  	return 0;
  }
  
  /**

   * __blkdev_issue_zeroout - generate number of zero filed write bios

   * @bdev:	blockdev to issue
   * @sector:	start sector
   * @nr_sects:	number of sectors to write
   * @gfp_mask:	memory allocation flags (for bio_alloc)

   * @biop:	pointer to anchor bio
   * @discard:	discard flag

   *
   * Description:
   *  Generate and issue number of bios with zerofiled pages.

   */

  int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
  		sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
  		bool discard)

  {

  	int ret;

  	int bi_size = 0;
  	struct bio *bio = *biop;

  	unsigned int sz;

  	sector_t bs_mask;
  
  	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
  	if ((sector | nr_sects) & bs_mask)
  		return -EINVAL;

  	if (discard) {
  		ret = __blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask,
  				BLKDEV_DISCARD_ZERO, biop);
  		if (ret == 0 || (ret && ret != -EOPNOTSUPP))
  			goto out;
  	}

  	ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp_mask,
  			biop);
  	if (ret == 0 || (ret && ret != -EOPNOTSUPP))
  		goto out;

  	ret = __blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask,
  			ZERO_PAGE(0), biop);
  	if (ret == 0 || (ret && ret != -EOPNOTSUPP))
  		goto out;
  
  	ret = 0;

  	while (nr_sects != 0) {

  		bio = next_bio(bio, min(nr_sects, (sector_t)BIO_MAX_PAGES),

  				gfp_mask);

  		bio->bi_iter.bi_sector = sector;

  		bio->bi_bdev   = bdev;

  		bio_set_op_attrs(bio, REQ_OP_WRITE, 0);

  		while (nr_sects != 0) {
  			sz = min((sector_t) PAGE_SIZE >> 9 , nr_sects);

  			bi_size = bio_add_page(bio, ZERO_PAGE(0), sz << 9, 0);
  			nr_sects -= bi_size >> 9;
  			sector += bi_size >> 9;
  			if (bi_size < (sz << 9))

  				break;
  		}

  		cond_resched();

  	}

  	*biop = bio;
  out:
  	return ret;

  }

  EXPORT_SYMBOL(__blkdev_issue_zeroout);

  
  /**
   * blkdev_issue_zeroout - zero-fill a block range
   * @bdev:	blockdev to write
   * @sector:	start sector
   * @nr_sects:	number of sectors to write
   * @gfp_mask:	memory allocation flags (for bio_alloc)

   * @discard:	whether to discard the block range

   *
   * Description:

   *  Zero-fill a block range.  If the discard flag is set and the block
   *  device guarantees that subsequent READ operations to the block range
   *  in question will return zeroes, the blocks will be discarded. Should
   *  the discard request fail, if the discard flag is not set, or if
   *  discard_zeroes_data is not supported, this function will resort to
   *  zeroing the blocks manually, thus provisioning (allocating,

   *  anchoring) them. If the block device supports WRITE ZEROES or WRITE SAME
   *  command(s), blkdev_issue_zeroout() will use it to optimize the process of

   *  clearing the block range. Otherwise the zeroing will be performed
   *  using regular WRITE calls.

   */

  int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,

  			 sector_t nr_sects, gfp_t gfp_mask, bool discard)

  {

  	int ret;
  	struct bio *bio = NULL;
  	struct blk_plug plug;

  	blk_start_plug(&plug);
  	ret = __blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask,
  			&bio, discard);
  	if (ret == 0 && bio) {
  		ret = submit_bio_wait(bio);
  		bio_put(bio);
  	}
  	blk_finish_plug(&plug);

  	return ret;

  }

  EXPORT_SYMBOL(blkdev_issue_zeroout);