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    Subject[PATCH 03/17] blk-map: improve alignment checking for blk_rq_map_user_iov()
    Date
    Impact: stricter more consistent alignment checking

    Move all alignment checks in blk_rq_map_user_iov() to
    __bio_map_user_iov() which has to walk the iov at the beginning
    anyway. Improve alignment check such that it checks for both the
    start address and length of each segment.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    ---
    block/blk-map.c | 21 +++++----------------
    fs/bio.c | 20 +++++++++++++-------
    2 files changed, 18 insertions(+), 23 deletions(-)

    diff --git a/block/blk-map.c b/block/blk-map.c
    index fdef591..b0b65ef 100644
    --- a/block/blk-map.c
    +++ b/block/blk-map.c
    @@ -67,28 +67,17 @@ 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 bio *bio = ERR_PTR(-EINVAL);
    + int read = rq_data_dir(rq) == READ;

    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)
    + if (!map_data)
    + bio = bio_map_user_iov(q, NULL, iov, iov_count, read, gfp_mask);
    + if (bio == ERR_PTR(-EINVAL))
    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);

    diff --git a/fs/bio.c b/fs/bio.c
    index 728bef9..80f61ed 100644
    --- a/fs/bio.c
    +++ b/fs/bio.c
    @@ -26,6 +26,7 @@
    #include <linux/mempool.h>
    #include <linux/workqueue.h>
    #include <linux/blktrace_api.h>
    +#include <linux/pfn.h>
    #include <trace/block.h>
    #include <scsi/sg.h> /* for struct sg_iovec */

    @@ -921,6 +922,7 @@ static struct bio *__bio_map_user_iov(struct request_queue *q,
    int write_to_vm, gfp_t gfp_mask)
    {
    int i, j;
    + size_t tot_len = 0;
    int nr_pages = 0;
    struct page **pages;
    struct bio *bio;
    @@ -930,18 +932,22 @@ static struct bio *__bio_map_user_iov(struct request_queue *q,
    for (i = 0; i < iov_count; i++) {
    unsigned long uaddr = (unsigned long)iov[i].iov_base;
    unsigned long len = iov[i].iov_len;
    - unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
    - unsigned long start = uaddr >> PAGE_SHIFT;

    - nr_pages += end - start;
    + nr_pages += PFN_UP(uaddr + len) - PFN_DOWN(uaddr);
    + tot_len += len;
    +
    /*
    - * buffer must be aligned to at least hardsector size for now
    + * Each segment must be aligned on DMA boundary. The
    + * last one may have unaligned length as long as the
    + * total length is aligned to DMA padding alignment.
    */
    - if (uaddr & queue_dma_alignment(q))
    + if (i == count - 1)
    + len = 0;
    + if ((uaddr | len) & queue_dma_alignment(q))
    return ERR_PTR(-EINVAL);
    }
    -
    - if (!nr_pages)
    + /* and total length on DMA padding alignment */
    + if (!nr_pages || tot_len & q->dma_pad_mask)
    return ERR_PTR(-EINVAL);

    bio = bio_kmalloc(gfp_mask, nr_pages);
    --
    1.6.0.2


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