/*
   * Functions related to mapping data to requests
   */
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/bio.h>
  #include <linux/blkdev.h>

  #include <linux/uio.h>

  
  #include "blk.h"

  /*
   * Append a bio to a passthrough request.  Only works can be merged into
   * the request based on the driver constraints.
   */
  int blk_rq_append_bio(struct request *rq, struct bio *bio)

  {

  	if (!rq->bio) {
  		blk_rq_bio_prep(rq->q, rq, bio);
  	} else {
  		if (!ll_back_merge_fn(rq->q, rq, bio))
  			return -EINVAL;

  		rq->biotail->bi_next = bio;
  		rq->biotail = bio;

  		rq->__data_len += bio->bi_iter.bi_size;

  	}

  	return 0;
  }

  EXPORT_SYMBOL(blk_rq_append_bio);

  
  static int __blk_rq_unmap_user(struct bio *bio)
  {
  	int ret = 0;
  
  	if (bio) {
  		if (bio_flagged(bio, BIO_USER_MAPPED))
  			bio_unmap_user(bio);
  		else
  			ret = bio_uncopy_user(bio);
  	}
  
  	return ret;
  }

  static int __blk_rq_map_user_iov(struct request *rq,
  		struct rq_map_data *map_data, struct iov_iter *iter,
  		gfp_t gfp_mask, bool copy)
  {
  	struct request_queue *q = rq->q;
  	struct bio *bio, *orig_bio;
  	int ret;
  
  	if (copy)
  		bio = bio_copy_user_iov(q, map_data, iter, gfp_mask);
  	else
  		bio = bio_map_user_iov(q, iter, gfp_mask);
  
  	if (IS_ERR(bio))
  		return PTR_ERR(bio);
  
  	if (map_data && map_data->null_mapped)
  		bio_set_flag(bio, BIO_NULL_MAPPED);
  
  	iov_iter_advance(iter, bio->bi_iter.bi_size);
  	if (map_data)
  		map_data->offset += bio->bi_iter.bi_size;
  
  	orig_bio = bio;
  	blk_queue_bounce(q, &bio);
  
  	/*
  	 * We link the bounce buffer in and could have to traverse it
  	 * later so we have to get a ref to prevent it from being freed
  	 */
  	bio_get(bio);

  	ret = blk_rq_append_bio(rq, bio);

  	if (ret) {
  		bio_endio(bio);
  		__blk_rq_unmap_user(orig_bio);
  		bio_put(bio);
  		return ret;
  	}
  
  	return 0;
  }

  /**

   * blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage

   * @q:		request queue where request should be inserted
   * @rq:		request to map data to

   * @map_data:   pointer to the rq_map_data holding pages (if necessary)

   * @iter:	iovec iterator

   * @gfp_mask:	memory allocation flags

   *
   * Description:

   *    Data will be mapped directly for zero copy I/O, if possible. Otherwise

   *    a kernel bounce buffer is used.
   *

   *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while

   *    still in process context.
   *
   *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
   *    before being submitted to the device, as pages mapped may be out of
   *    reach. It's the callers responsibility to make sure this happens. The
   *    original bio must be passed back in to blk_rq_unmap_user() for proper
   *    unmapping.
   */
  int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,

  			struct rq_map_data *map_data,
  			const struct iov_iter *iter, gfp_t gfp_mask)

  {

  	bool copy = false;
  	unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);

  	struct bio *bio = NULL;
  	struct iov_iter i;
  	int ret;

  	if (map_data)
  		copy = true;
  	else if (iov_iter_alignment(iter) & align)
  		copy = true;
  	else if (queue_virt_boundary(q))
  		copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);

  	i = *iter;
  	do {
  		ret =__blk_rq_map_user_iov(rq, map_data, &i, gfp_mask, copy);
  		if (ret)
  			goto unmap_rq;
  		if (!bio)
  			bio = rq->bio;
  	} while (iov_iter_count(&i));

  	if (!bio_flagged(bio, BIO_USER_MAPPED))
  		rq->cmd_flags |= REQ_COPY_USER;

  	return 0;

  
  unmap_rq:
  	__blk_rq_unmap_user(bio);
  	rq->bio = NULL;
  	return -EINVAL;

  }

  EXPORT_SYMBOL(blk_rq_map_user_iov);

  int blk_rq_map_user(struct request_queue *q, struct request *rq,
  		    struct rq_map_data *map_data, void __user *ubuf,
  		    unsigned long len, gfp_t gfp_mask)
  {

  	struct iovec iov;
  	struct iov_iter i;

  	int ret = import_single_range(rq_data_dir(rq), ubuf, len, &iov, &i);

  	if (unlikely(ret < 0))
  		return ret;

  	return blk_rq_map_user_iov(q, rq, map_data, &i, gfp_mask);

  }
  EXPORT_SYMBOL(blk_rq_map_user);

  /**
   * blk_rq_unmap_user - unmap a request with user data
   * @bio:	       start of bio list
   *
   * Description:
   *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
   *    supply the original rq->bio from the blk_rq_map_user() return, since

   *    the I/O completion may have changed rq->bio.

   */
  int blk_rq_unmap_user(struct bio *bio)
  {
  	struct bio *mapped_bio;
  	int ret = 0, ret2;
  
  	while (bio) {
  		mapped_bio = bio;
  		if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
  			mapped_bio = bio->bi_private;
  
  		ret2 = __blk_rq_unmap_user(mapped_bio);
  		if (ret2 && !ret)
  			ret = ret2;
  
  		mapped_bio = bio;
  		bio = bio->bi_next;
  		bio_put(mapped_bio);
  	}
  
  	return ret;
  }

  EXPORT_SYMBOL(blk_rq_unmap_user);
  
  /**

   * blk_rq_map_kern - map kernel data to a request, for REQ_TYPE_BLOCK_PC usage

   * @q:		request queue where request should be inserted
   * @rq:		request to fill
   * @kbuf:	the kernel buffer
   * @len:	length of user data
   * @gfp_mask:	memory allocation flags

   *
   * Description:
   *    Data will be mapped directly if possible. Otherwise a bounce

   *    buffer is used. Can be called multiple times to append multiple

   *    buffers.

   */
  int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
  		    unsigned int len, gfp_t gfp_mask)
  {

  	int reading = rq_data_dir(rq) == READ;

  	unsigned long addr = (unsigned long) kbuf;

  	int do_copy = 0;

  	struct bio *bio;

  	int ret;

  	if (len > (queue_max_hw_sectors(q) << 9))

  		return -EINVAL;
  	if (!len || !kbuf)
  		return -EINVAL;

  	do_copy = !blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf);

  	if (do_copy)
  		bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
  	else
  		bio = bio_map_kern(q, kbuf, len, gfp_mask);

  	if (IS_ERR(bio))
  		return PTR_ERR(bio);

  	if (!reading)

  		bio_set_op_attrs(bio, REQ_OP_WRITE, 0);

  	if (do_copy)
  		rq->cmd_flags |= REQ_COPY_USER;

  	ret = blk_rq_append_bio(rq, bio);

  	if (unlikely(ret)) {
  		/* request is too big */
  		bio_put(bio);
  		return ret;
  	}

  	blk_queue_bounce(q, &rq->bio);

  	return 0;
  }

  EXPORT_SYMBOL(blk_rq_map_kern);