/*
 * 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"

static bool iovec_gap_to_prv(struct request_queue *q,
                             struct sg_iovec *prv, struct sg_iovec *cur)
{
        unsigned long prev_end;

        if (!queue_virt_boundary(q))
                return false;

        if (prv->iov_base == NULL && prv->iov_len == 0)
                /* prv is not set - don't check */
                return false;

        prev_end = (unsigned long)(prv->iov_base + prv->iov_len);

        return (((unsigned long)cur->iov_base & queue_virt_boundary(q)) ||
                prev_end & queue_virt_boundary(q));
}

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, uaddr, 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;
        struct sg_iovec prv = {.iov_base = NULL, .iov_len = 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 (!iov[i].iov_len)
                        return -EINVAL;

                /*
                 * Keep going so we check length of all segments
                 */
                if (uaddr & queue_dma_alignment(q) ||
                    iovec_gap_to_prv(q, &prv, &iov[i]))
                        unaligned = 1;

                prv.iov_base = iov[i].iov_base;
                prv.iov_len = iov[i].iov_len;
        }

        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;
        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->bi_rw |= REQ_WRITE;

        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);