[PATCH v2 hmm 02/11] mm/hmm: Use hmm_mirror not mm as an argument for hmm_range_register
Ralph Campbell
rcampbell at nvidia.com
Fri Jun 7 22:39:06 UTC 2019
On 6/7/19 11:24 AM, Ralph Campbell wrote:
>
> On 6/6/19 11:44 AM, Jason Gunthorpe wrote:
>> From: Jason Gunthorpe <jgg at mellanox.com>
>>
>> Ralph observes that hmm_range_register() can only be called by a driver
>> while a mirror is registered. Make this clear in the API by passing in
>> the
>> mirror structure as a parameter.
>>
>> This also simplifies understanding the lifetime model for struct hmm, as
>> the hmm pointer must be valid as part of a registered mirror so all we
>> need in hmm_register_range() is a simple kref_get.
>>
>> Suggested-by: Ralph Campbell <rcampbell at nvidia.com>
>> Signed-off-by: Jason Gunthorpe <jgg at mellanox.com>
>
> You might CC Ben for the nouveau part.
> CC: Ben Skeggs <bskeggs at redhat.com>
>
> Reviewed-by: Ralph Campbell <rcampbell at nvidia.com>
>
>
>> ---
>> v2
>> - Include the oneline patch to nouveau_svm.c
>> ---
>> drivers/gpu/drm/nouveau/nouveau_svm.c | 2 +-
>> include/linux/hmm.h | 7 ++++---
>> mm/hmm.c | 15 ++++++---------
>> 3 files changed, 11 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c
>> b/drivers/gpu/drm/nouveau/nouveau_svm.c
>> index 93ed43c413f0bb..8c92374afcf227 100644
>> --- a/drivers/gpu/drm/nouveau/nouveau_svm.c
>> +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
>> @@ -649,7 +649,7 @@ nouveau_svm_fault(struct nvif_notify *notify)
>> range.values = nouveau_svm_pfn_values;
>> range.pfn_shift = NVIF_VMM_PFNMAP_V0_ADDR_SHIFT;
>> again:
>> - ret = hmm_vma_fault(&range, true);
>> + ret = hmm_vma_fault(&svmm->mirror, &range, true);
>> if (ret == 0) {
>> mutex_lock(&svmm->mutex);
>> if (!hmm_vma_range_done(&range)) {
>> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
>> index 688c5ca7068795..2d519797cb134a 100644
>> --- a/include/linux/hmm.h
>> +++ b/include/linux/hmm.h
>> @@ -505,7 +505,7 @@ static inline bool hmm_mirror_mm_is_alive(struct
>> hmm_mirror *mirror)
>> * Please see Documentation/vm/hmm.rst for how to use the range API.
>> */
>> int hmm_range_register(struct hmm_range *range,
>> - struct mm_struct *mm,
>> + struct hmm_mirror *mirror,
>> unsigned long start,
>> unsigned long end,
>> unsigned page_shift);
>> @@ -541,7 +541,8 @@ static inline bool hmm_vma_range_done(struct
>> hmm_range *range)
>> }
>> /* This is a temporary helper to avoid merge conflict between trees. */
>> -static inline int hmm_vma_fault(struct hmm_range *range, bool block)
>> +static inline int hmm_vma_fault(struct hmm_mirror *mirror,
>> + struct hmm_range *range, bool block)
>> {
>> long ret;
>> @@ -554,7 +555,7 @@ static inline int hmm_vma_fault(struct hmm_range
>> *range, bool block)
>> range->default_flags = 0;
>> range->pfn_flags_mask = -1UL;
>> - ret = hmm_range_register(range, range->vma->vm_mm,
>> + ret = hmm_range_register(range, mirror,
>> range->start, range->end,
>> PAGE_SHIFT);
>> if (ret)
>> diff --git a/mm/hmm.c b/mm/hmm.c
>> index 547002f56a163d..8796447299023c 100644
>> --- a/mm/hmm.c
>> +++ b/mm/hmm.c
>> @@ -925,13 +925,13 @@ static void hmm_pfns_clear(struct hmm_range *range,
>> * Track updates to the CPU page table see include/linux/hmm.h
>> */
>> int hmm_range_register(struct hmm_range *range,
>> - struct mm_struct *mm,
>> + struct hmm_mirror *mirror,
>> unsigned long start,
>> unsigned long end,
>> unsigned page_shift)
>> {
>> unsigned long mask = ((1UL << page_shift) - 1UL);
>> - struct hmm *hmm;
>> + struct hmm *hmm = mirror->hmm;
>> range->valid = false;
>> range->hmm = NULL;
>> @@ -945,15 +945,12 @@ int hmm_range_register(struct hmm_range *range,
>> range->start = start;
>> range->end = end;
>> - hmm = hmm_get_or_create(mm);
>> - if (!hmm)
>> - return -EFAULT;
>> -
>> /* Check if hmm_mm_destroy() was call. */
>> - if (hmm->mm == NULL || hmm->dead) {
>> - hmm_put(hmm);
>> + if (hmm->mm == NULL || hmm->dead)
>> return -EFAULT;
>> - }
>> +
>> + range->hmm = hmm;
>> + kref_get(&hmm->kref);
>> /* Initialize range to track CPU page table updates. */
>> mutex_lock(&hmm->lock);
>>
I forgot to add that I think you can delete the duplicate
"range->hmm = hmm;"
here between the mutex_lock/unlock.
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