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    Subject[RFC PATCH 03/28] block: Warn on mis-use of dma-direct bios
    This is a result of an audit of users of 'bi_io_vec'. A number of
    warnings and blocking conditions are added to ensure dma-direct bios
    are not incorrectly accessing the 'bi_io_vec' when they should access
    the 'bi_dma_vec'. These are largely just protecting against mis-uses
    in future development so depending on taste and public opinion some
    or all of these checks may not be necessary.

    A few other issues with dma-direct bios will be tackled in subsequent
    patches.

    Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
    ---
    block/bio.c | 33 +++++++++++++++++++++++++++++++++
    block/blk-core.c | 3 +++
    2 files changed, 36 insertions(+)

    diff --git a/block/bio.c b/block/bio.c
    index 683cbb40f051..6998fceddd36 100644
    --- a/block/bio.c
    +++ b/block/bio.c
    @@ -525,6 +525,9 @@ void zero_fill_bio_iter(struct bio *bio, struct bvec_iter start)
    struct bio_vec bv;
    struct bvec_iter iter;

    + if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
    + return;
    +
    __bio_for_each_segment(bv, bio, iter, start) {
    char *data = bvec_kmap_irq(&bv, &flags);
    memset(data, 0, bv.bv_len);
    @@ -707,6 +710,8 @@ static int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
    */
    if (unlikely(bio_flagged(bio, BIO_CLONED)))
    return 0;
    + if (unlikely(bio_is_dma_direct(bio)))
    + return 0;

    if (((bio->bi_iter.bi_size + len) >> 9) > queue_max_hw_sectors(q))
    return 0;
    @@ -783,6 +788,8 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
    {
    if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
    return false;
    + if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
    + return false;

    if (bio->bi_vcnt > 0) {
    struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
    @@ -814,6 +821,7 @@ void __bio_add_page(struct bio *bio, struct page *page,

    WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED));
    WARN_ON_ONCE(bio_full(bio));
    + WARN_ON_ONCE(bio_is_dma_direct(bio));

    bv->bv_page = page;
    bv->bv_offset = off;
    @@ -851,6 +859,8 @@ static void bio_get_pages(struct bio *bio)
    struct bvec_iter_all iter_all;
    struct bio_vec *bvec;

    + WARN_ON_ONCE(bio_is_dma_direct(bio));
    +
    bio_for_each_segment_all(bvec, bio, iter_all)
    get_page(bvec->bv_page);
    }
    @@ -956,6 +966,8 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)

    if (WARN_ON_ONCE(bio->bi_vcnt))
    return -EINVAL;
    + if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
    + return -EINVAL;

    do {
    if (is_bvec)
    @@ -1029,6 +1041,9 @@ void bio_copy_data_iter(struct bio *dst, struct bvec_iter *dst_iter,
    void *src_p, *dst_p;
    unsigned bytes;

    + if (WARN_ON_ONCE(bio_is_dma_direct(src) || bio_is_dma_direct(dst)))
    + return;
    +
    while (src_iter->bi_size && dst_iter->bi_size) {
    src_bv = bio_iter_iovec(src, *src_iter);
    dst_bv = bio_iter_iovec(dst, *dst_iter);
    @@ -1143,6 +1158,9 @@ static int bio_copy_from_iter(struct bio *bio, struct iov_iter *iter)
    struct bio_vec *bvec;
    struct bvec_iter_all iter_all;

    + if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
    + return -EINVAL;
    +
    bio_for_each_segment_all(bvec, bio, iter_all) {
    ssize_t ret;

    @@ -1174,6 +1192,9 @@ static int bio_copy_to_iter(struct bio *bio, struct iov_iter iter)
    struct bio_vec *bvec;
    struct bvec_iter_all iter_all;

    + if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
    + return -EINVAL;
    +
    bio_for_each_segment_all(bvec, bio, iter_all) {
    ssize_t ret;

    @@ -1197,6 +1218,9 @@ void bio_free_pages(struct bio *bio)
    struct bio_vec *bvec;
    struct bvec_iter_all iter_all;

    + if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
    + return;
    +
    bio_for_each_segment_all(bvec, bio, iter_all)
    __free_page(bvec->bv_page);
    }
    @@ -1653,6 +1677,9 @@ void bio_set_pages_dirty(struct bio *bio)
    struct bio_vec *bvec;
    struct bvec_iter_all iter_all;

    + if (unlikely(bio_is_dma_direct(bio)))
    + return;
    +
    bio_for_each_segment_all(bvec, bio, iter_all) {
    if (!PageCompound(bvec->bv_page))
    set_page_dirty_lock(bvec->bv_page);
    @@ -1704,6 +1731,9 @@ void bio_check_pages_dirty(struct bio *bio)
    unsigned long flags;
    struct bvec_iter_all iter_all;

    + if (unlikely(bio_is_dma_direct(bio)))
    + return;
    +
    bio_for_each_segment_all(bvec, bio, iter_all) {
    if (!PageDirty(bvec->bv_page) && !PageCompound(bvec->bv_page))
    goto defer;
    @@ -1777,6 +1807,9 @@ void bio_flush_dcache_pages(struct bio *bi)
    struct bio_vec bvec;
    struct bvec_iter iter;

    + if (unlikely(bio_is_dma_direct(bi)))
    + return;
    +
    bio_for_each_segment(bvec, bi, iter)
    flush_dcache_page(bvec.bv_page);
    }
    diff --git a/block/blk-core.c b/block/blk-core.c
    index 8340f69670d8..ea152d54c7ce 100644
    --- a/block/blk-core.c
    +++ b/block/blk-core.c
    @@ -1467,6 +1467,9 @@ void rq_flush_dcache_pages(struct request *rq)
    struct req_iterator iter;
    struct bio_vec bvec;

    + if (unlikely(blk_rq_is_dma_direct(rq)))
    + return;
    +
    rq_for_each_segment(bvec, rq, iter)
    flush_dcache_page(bvec.bv_page);
    }
    --
    2.20.1
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