/*
 * Functions related to mapping data to requests
 */
#include <linux/kernel.h>
#include <linux/sched/task_stack.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)
{
        blk_queue_bounce(rq->q, &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);

        bio->bi_opf &= ~REQ_OP_MASK;
        bio->bi_opf |= req_op(rq);

        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;

        /*
         * 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
         */
        ret = blk_rq_append_bio(rq, bio);
        bio_get(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 passthrough requests
 * @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 (!iter_is_iovec(iter))
                goto fail;

        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->rq_flags |= RQF_COPY_USER;
        return 0;

unmap_rq:
        __blk_rq_unmap_user(bio);
fail:
        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 passthrough requests
 * @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);

        bio->bi_opf &= ~REQ_OP_MASK;
        bio->bi_opf |= req_op(rq);

        if (do_copy)
                rq->rq_flags |= RQF_COPY_USER;

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

        return 0;
}
EXPORT_SYMBOL(blk_rq_map_kern);