blk-map.c

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/*
 * 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, 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;
}

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);

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 (!iov[i].iov_len)
            return -EINVAL;

        /*
         * Keep going so we check length of all segments
         */
        if (uaddr & queue_dma_alignment(q))
            unaligned = 1;
    }

    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);

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);

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);