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    Subject[PATCH v10 09/25] IB/umem: use get_user_pages_fast() to pin DMA pages
    Date
    And get rid of the mmap_sem calls, as part of that. Note
    that get_user_pages_fast() will, if necessary, fall back to
    __gup_longterm_unlocked(), which takes the mmap_sem as needed.

    Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Reviewed-by: Jan Kara <jack@suse.cz>
    Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
    Reviewed-by: Ira Weiny <ira.weiny@intel.com>
    Signed-off-by: John Hubbard <jhubbard@nvidia.com>
    ---
    drivers/infiniband/core/umem.c | 17 ++++++-----------
    1 file changed, 6 insertions(+), 11 deletions(-)

    diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
    index 7a3b99597ead..214e87aa609d 100644
    --- a/drivers/infiniband/core/umem.c
    +++ b/drivers/infiniband/core/umem.c
    @@ -266,16 +266,13 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr,
    sg = umem->sg_head.sgl;

    while (npages) {
    - down_read(&mm->mmap_sem);
    - ret = get_user_pages(cur_base,
    - min_t(unsigned long, npages,
    - PAGE_SIZE / sizeof (struct page *)),
    - gup_flags | FOLL_LONGTERM,
    - page_list, NULL);
    - if (ret < 0) {
    - up_read(&mm->mmap_sem);
    + ret = get_user_pages_fast(cur_base,
    + min_t(unsigned long, npages,
    + PAGE_SIZE /
    + sizeof(struct page *)),
    + gup_flags | FOLL_LONGTERM, page_list);
    + if (ret < 0)
    goto umem_release;
    - }

    cur_base += ret * PAGE_SIZE;
    npages -= ret;
    @@ -283,8 +280,6 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr,
    sg = ib_umem_add_sg_table(sg, page_list, ret,
    dma_get_max_seg_size(context->device->dma_device),
    &umem->sg_nents);
    -
    - up_read(&mm->mmap_sem);
    }

    sg_mark_end(sg);
    --
    2.24.0
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