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

  #include <scsi/sg.h>		/* for struct sg_iovec */

  
  #include "blk.h"
  
  int blk_rq_append_bio(struct request_queue *q, struct request *rq,
  		      struct bio *bio)
  {
  	if (!rq->bio)
  		blk_rq_bio_prep(q, rq, bio);
  	else if (!ll_back_merge_fn(q, rq, bio))
  		return -EINVAL;
  	else {
  		rq->biotail->bi_next = bio;
  		rq->biotail = bio;

  		rq->__data_len += bio->bi_size;

  	}
  	return 0;
  }

  
  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(struct request_queue *q, struct request *rq,

  			     struct rq_map_data *map_data, void __user *ubuf,

  			     unsigned int len, gfp_t gfp_mask)

  {
  	unsigned long uaddr;
  	struct bio *bio, *orig_bio;
  	int reading, ret;
  
  	reading = rq_data_dir(rq) == READ;
  
  	/*
  	 * if alignment requirement is satisfied, map in user pages for
  	 * direct dma. else, set up kernel bounce buffers
  	 */
  	uaddr = (unsigned long) ubuf;

  	if (blk_rq_aligned(q, ubuf, len) && !map_data)

  		bio = bio_map_user(q, NULL, uaddr, len, reading, gfp_mask);

  	else

  		bio = bio_copy_user(q, map_data, uaddr, len, reading, gfp_mask);

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

  	if (map_data && map_data->null_mapped)

  		bio->bi_flags |= (1 << BIO_NULL_MAPPED);

  	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(q, rq, bio);
  	if (!ret)
  		return bio->bi_size;
  
  	/* if it was boucned we must call the end io function */
  	bio_endio(bio, 0);
  	__blk_rq_unmap_user(orig_bio);
  	bio_put(bio);
  	return ret;
  }
  
  /**

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

   * @q:		request queue where request should be inserted
   * @rq:		request structure to fill

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

   * @ubuf:	the user buffer
   * @len:	length of user data

   * @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(struct request_queue *q, struct request *rq,

  		    struct rq_map_data *map_data, void __user *ubuf,
  		    unsigned long len, gfp_t gfp_mask)

  {
  	unsigned long bytes_read = 0;
  	struct bio *bio = NULL;

  	int ret;

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

  		return -EINVAL;

  	if (!len)

  		return -EINVAL;

  
  	if (!ubuf && (!map_data || !map_data->null_mapped))
  		return -EINVAL;

  
  	while (bytes_read != len) {
  		unsigned long map_len, end, start;
  
  		map_len = min_t(unsigned long, len - bytes_read, BIO_MAX_SIZE);
  		end = ((unsigned long)ubuf + map_len + PAGE_SIZE - 1)
  								>> PAGE_SHIFT;
  		start = (unsigned long)ubuf >> PAGE_SHIFT;
  
  		/*
  		 * A bad offset could cause us to require BIO_MAX_PAGES + 1
  		 * pages. If this happens we just lower the requested
  		 * mapping len by a page so that we can fit
  		 */
  		if (end - start > BIO_MAX_PAGES)
  			map_len -= PAGE_SIZE;

  		ret = __blk_rq_map_user(q, rq, map_data, ubuf, map_len,

  					gfp_mask);

  		if (ret < 0)
  			goto unmap_rq;
  		if (!bio)
  			bio = rq->bio;
  		bytes_read += ret;
  		ubuf += ret;

  
  		if (map_data)
  			map_data->offset += ret;

  	}

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

  	rq->buffer = NULL;

  	return 0;
  unmap_rq:
  	blk_rq_unmap_user(bio);

  	rq->bio = NULL;

  	return ret;
  }

  EXPORT_SYMBOL(blk_rq_map_user);
  
  /**

   * 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)

   * @iov:	pointer to the iovec
   * @iov_count:	number of elements in the iovec
   * @len:	I/O byte count

   * @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, struct sg_iovec *iov,
  			int iov_count, unsigned int len, gfp_t gfp_mask)

  {
  	struct bio *bio;

  	int i, read = rq_data_dir(rq) == READ;
  	int unaligned = 0;

  
  	if (!iov || iov_count <= 0)
  		return -EINVAL;

  	for (i = 0; i < iov_count; i++) {
  		unsigned long uaddr = (unsigned long)iov[i].iov_base;
  
  		if (uaddr & queue_dma_alignment(q)) {
  			unaligned = 1;
  			break;
  		}
  	}

  	if (unaligned || (q->dma_pad_mask & len) || map_data)
  		bio = bio_copy_user_iov(q, map_data, iov, iov_count, read,
  					gfp_mask);

  	else

  		bio = bio_map_user_iov(q, NULL, iov, iov_count, read, gfp_mask);

  	if (IS_ERR(bio))
  		return PTR_ERR(bio);
  
  	if (bio->bi_size != len) {

  		/*
  		 * Grab an extra reference to this bio, as bio_unmap_user()
  		 * expects to be able to drop it twice as it happens on the
  		 * normal IO completion path
  		 */
  		bio_get(bio);

  		bio_endio(bio, 0);

  		__blk_rq_unmap_user(bio);

  		return -EINVAL;
  	}

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

  	blk_queue_bounce(q, &bio);

  	bio_get(bio);
  	blk_rq_bio_prep(q, rq, bio);

  	rq->buffer = NULL;

  	return 0;
  }

  EXPORT_SYMBOL(blk_rq_map_user_iov);

  
  /**
   * 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 multple times to append multple
   *    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;
  	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, kbuf, 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 (rq_data_dir(rq) == WRITE)
  		bio->bi_rw |= (1 << BIO_RW);

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

  	ret = blk_rq_append_bio(q, rq, bio);
  	if (unlikely(ret)) {
  		/* request is too big */
  		bio_put(bio);
  		return ret;
  	}

  	blk_queue_bounce(q, &rq->bio);

  	rq->buffer = NULL;

  	return 0;
  }

  EXPORT_SYMBOL(blk_rq_map_kern);