/*
   * 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"

  struct bio_batch {
  	atomic_t		done;
  	unsigned long		flags;
  	struct completion	*wait;
  };
  
  static void bio_batch_end_io(struct bio *bio, int err)

  {

  	struct bio_batch *bb = bio->bi_private;

  	if (err && (err != -EOPNOTSUPP))

  		clear_bit(BIO_UPTODATE, &bb->flags);

  	if (atomic_dec_and_test(&bb->done))
  		complete(bb->wait);

  	bio_put(bio);
  }
  
  /**
   * 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)
  {
  	DECLARE_COMPLETION_ONSTACK(wait);
  	struct request_queue *q = bdev_get_queue(bdev);

  	int type = REQ_WRITE | REQ_DISCARD;

  	unsigned int max_discard_sectors;

  	struct bio_batch bb;

  	struct bio *bio;

  	int ret = 0;
  
  	if (!q)
  		return -ENXIO;
  
  	if (!blk_queue_discard(q))
  		return -EOPNOTSUPP;

  	/*
  	 * Ensure that max_discard_sectors is of the proper
  	 * granularity
  	 */
  	max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);

  	if (unlikely(!max_discard_sectors)) {

  		/* Avoid infinite loop below. Being cautious never hurts. */
  		return -EOPNOTSUPP;
  	} else if (q->limits.discard_granularity) {

  		unsigned int disc_sects = q->limits.discard_granularity >> 9;
  
  		max_discard_sectors &= ~(disc_sects - 1);
  	}

  	if (flags & BLKDEV_DISCARD_SECURE) {

  		if (!blk_queue_secdiscard(q))
  			return -EOPNOTSUPP;

  		type |= REQ_SECURE;

  	}

  	atomic_set(&bb.done, 1);
  	bb.flags = 1 << BIO_UPTODATE;
  	bb.wait = &wait;
  
  	while (nr_sects) {

  		bio = bio_alloc(gfp_mask, 1);

  		if (!bio) {
  			ret = -ENOMEM;
  			break;
  		}

  		bio->bi_sector = sector;

  		bio->bi_end_io = bio_batch_end_io;

  		bio->bi_bdev = bdev;

  		bio->bi_private = &bb;

  		if (nr_sects > max_discard_sectors) {
  			bio->bi_size = max_discard_sectors << 9;
  			nr_sects -= max_discard_sectors;
  			sector += max_discard_sectors;
  		} else {
  			bio->bi_size = nr_sects << 9;
  			nr_sects = 0;
  		}

  		atomic_inc(&bb.done);

  		submit_bio(type, bio);

  	}

  	/* Wait for bios in-flight */
  	if (!atomic_dec_and_test(&bb.done))

  		wait_for_completion(&wait);

  	if (!test_bit(BIO_UPTODATE, &bb.flags))

  		ret = -EIO;

  	return ret;

  }
  EXPORT_SYMBOL(blkdev_issue_discard);

  /**

   * 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)

   *
   * 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)

  {

  	int ret;

  	struct bio *bio;
  	struct bio_batch bb;

  	unsigned int sz;

  	DECLARE_COMPLETION_ONSTACK(wait);

  	atomic_set(&bb.done, 1);

  	bb.flags = 1 << BIO_UPTODATE;
  	bb.wait = &wait;

  	ret = 0;

  	while (nr_sects != 0) {
  		bio = bio_alloc(gfp_mask,
  				min(nr_sects, (sector_t)BIO_MAX_PAGES));

  		if (!bio) {
  			ret = -ENOMEM;

  			break;

  		}

  
  		bio->bi_sector = sector;
  		bio->bi_bdev   = bdev;
  		bio->bi_end_io = bio_batch_end_io;

  		bio->bi_private = &bb;

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

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

  		ret = 0;

  		atomic_inc(&bb.done);

  		submit_bio(WRITE, bio);
  	}

  	/* Wait for bios in-flight */

  	if (!atomic_dec_and_test(&bb.done))

  		wait_for_completion(&wait);

  
  	if (!test_bit(BIO_UPTODATE, &bb.flags))
  		/* One of bios in the batch was completed with error.*/
  		ret = -EIO;

  	return ret;
  }
  EXPORT_SYMBOL(blkdev_issue_zeroout);