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    Subject[PATCH RFC 11/19] RDMA/usnic: remove FOLL_FORCE usage
    Date
    GUP now supports reliable R/O long-term pinning in COW mappings, such
    that we break COW early. MAP_SHARED VMAs only use the shared zeropage so
    far in one corner case (DAXFS file with holes), which can be ignored
    because GUP does not support long-term pinning in fsdax (see
    check_vma_flags()).

    Consequently, FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM is no longer required
    for reliable R/O long-term pinning: FOLL_LONGTERM is sufficient. So stop
    using FOLL_FORCE, which is really only for debugger access.

    Cc: Christian Benvenuti <benve@cisco.com>
    Cc: Nelson Escobar <neescoba@cisco.com>
    Cc: Jason Gunthorpe <jgg@ziepe.ca>
    Cc: Leon Romanovsky <leon@kernel.org>
    Signed-off-by: David Hildenbrand <david@redhat.com>
    ---
    drivers/infiniband/hw/usnic/usnic_uiom.c | 9 ++++-----
    1 file changed, 4 insertions(+), 5 deletions(-)

    diff --git a/drivers/infiniband/hw/usnic/usnic_uiom.c b/drivers/infiniband/hw/usnic/usnic_uiom.c
    index 67923ced6e2d..c301b3be9f30 100644
    --- a/drivers/infiniband/hw/usnic/usnic_uiom.c
    +++ b/drivers/infiniband/hw/usnic/usnic_uiom.c
    @@ -85,6 +85,7 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
    int dmasync, struct usnic_uiom_reg *uiomr)
    {
    struct list_head *chunk_list = &uiomr->chunk_list;
    + unsigned int gup_flags = FOLL_LONGTERM;
    struct page **page_list;
    struct scatterlist *sg;
    struct usnic_uiom_chunk *chunk;
    @@ -96,7 +97,6 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
    int off;
    int i;
    dma_addr_t pa;
    - unsigned int gup_flags;
    struct mm_struct *mm;

    /*
    @@ -131,8 +131,8 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
    goto out;
    }

    - gup_flags = FOLL_WRITE;
    - gup_flags |= (writable) ? 0 : FOLL_FORCE;
    + if (writable)
    + gup_flags |= FOLL_WRITE;
    cur_base = addr & PAGE_MASK;
    ret = 0;

    @@ -140,8 +140,7 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
    ret = pin_user_pages(cur_base,
    min_t(unsigned long, npages,
    PAGE_SIZE / sizeof(struct page *)),
    - gup_flags | FOLL_LONGTERM,
    - page_list, NULL);
    + gup_flags, page_list, NULL);

    if (ret < 0)
    goto out;
    --
    2.38.1
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