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    Subject[PATCH 01/15] amdgpu: remove -EAGAIN handling for hmm_range_fault
    Date
    hmm_range_fault can only return -EAGAIN if called with the
    HMM_FAULT_ALLOW_RETRY flag, which amdgpu never does. Remove the
    handling for the -EAGAIN case with its non-standard locking scheme.

    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
    Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
    ---
    drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 23 +++--------------------
    1 file changed, 3 insertions(+), 20 deletions(-)

    diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
    index 12a59ac83f72..f0821638bbc6 100644
    --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
    +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
    @@ -778,7 +778,6 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
    struct hmm_range *range;
    unsigned long i;
    uint64_t *pfns;
    - int retry = 0;
    int r = 0;

    if (!mm) /* Happens during process shutdown */
    @@ -822,7 +821,6 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
    hmm_range_register(range, mirror, start,
    start + ttm->num_pages * PAGE_SIZE, PAGE_SHIFT);

    -retry:
    /*
    * Just wait for range to be valid, safe to ignore return value as we
    * will use the return value of hmm_range_fault() below under the
    @@ -831,24 +829,12 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
    hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT);

    down_read(&mm->mmap_sem);
    -
    r = hmm_range_fault(range, 0);
    - if (unlikely(r < 0)) {
    - if (likely(r == -EAGAIN)) {
    - /*
    - * return -EAGAIN, mmap_sem is dropped
    - */
    - if (retry++ < MAX_RETRY_HMM_RANGE_FAULT)
    - goto retry;
    - else
    - pr_err("Retry hmm fault too many times\n");
    - }
    -
    - goto out_up_read;
    - }
    -
    up_read(&mm->mmap_sem);

    + if (unlikely(r < 0))
    + goto out_free_pfns;
    +
    for (i = 0; i < ttm->num_pages; i++) {
    pages[i] = hmm_device_entry_to_page(range, pfns[i]);
    if (unlikely(!pages[i])) {
    @@ -864,9 +850,6 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)

    return 0;

    -out_up_read:
    - if (likely(r != -EAGAIN))
    - up_read(&mm->mmap_sem);
    out_free_pfns:
    hmm_range_unregister(range);
    kvfree(pfns);
    --
    2.20.1
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