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Date: Mon, 18 Jun 2018 15:20:37 +0200
From: Christian König <christian.koenig@....com>
To: Souptick Joarder <jrdr.linux@...il.com>, airlied@...ux.ie
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v2] gpu: drm: ttm: Adding new return type vm_fault_t
Am 08.06.2018 um 08:44 schrieb Christian König:
> Am 08.06.2018 um 06:36 schrieb Souptick Joarder:
>> On Sat, Jun 2, 2018 at 12:57 AM, Souptick Joarder
>> <jrdr.linux@...il.com> wrote:
>>> Use new return type vm_fault_t for fault handler. For
>>> now, this is just documenting that the function returns
>>> a VM_FAULT value rather than an errno. Once all instances
>>> are converted, vm_fault_t will become a distinct type.
>>>
>>> Ref-> commit 1c8f422059ae ("mm: change return type to vm_fault_t")
>>>
>>> Previously vm_insert_{mixed,pfn} returns err which driver
>>> mapped into VM_FAULT_* type. The new function
>>> vmf_insert_{mixed,pfn} will replace this inefficiency by
>>> returning VM_FAULT_* type.
>>>
>>> Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
>>> ---
>>> v2: Address christian's comment. Put reverse
>>> xmas tree order for variable declarations.
>>>
>>> drivers/gpu/drm/ttm/ttm_bo_vm.c | 45
>>> ++++++++++++++++++++---------------------
>>> 1 file changed, 22 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c
>>> b/drivers/gpu/drm/ttm/ttm_bo_vm.c
>>> index 8eba95b..9de8b4f 100644
>>> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
>>> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
>>> @@ -43,10 +43,11 @@
>>>
>>> #define TTM_BO_VM_NUM_PREFAULT 16
>>>
>>> -static int ttm_bo_vm_fault_idle(struct ttm_buffer_object *bo,
>>> +static vm_fault_t ttm_bo_vm_fault_idle(struct ttm_buffer_object *bo,
>>> struct vm_fault *vmf)
>>> {
>>> - int ret = 0;
>>> + vm_fault_t ret = 0;
>>> + int err = 0;
>>>
>>> if (likely(!bo->moving))
>>> goto out_unlock;
>>> @@ -77,9 +78,9 @@ static int ttm_bo_vm_fault_idle(struct
>>> ttm_buffer_object *bo,
>>> /*
>>> * Ordinary wait.
>>> */
>>> - ret = dma_fence_wait(bo->moving, true);
>>> - if (unlikely(ret != 0)) {
>>> - ret = (ret != -ERESTARTSYS) ? VM_FAULT_SIGBUS :
>>> + err = dma_fence_wait(bo->moving, true);
>>> + if (unlikely(err != 0)) {
>>> + ret = (err != -ERESTARTSYS) ? VM_FAULT_SIGBUS :
>>> VM_FAULT_NOPAGE;
>>> goto out_unlock;
>>> }
>>> @@ -104,7 +105,7 @@ static unsigned long ttm_bo_io_mem_pfn(struct
>>> ttm_buffer_object *bo,
>>> + page_offset;
>>> }
>>>
>>> -static int ttm_bo_vm_fault(struct vm_fault *vmf)
>>> +static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
>>> {
>>> struct vm_area_struct *vma = vmf->vma;
>>> struct ttm_buffer_object *bo = (struct ttm_buffer_object *)
>>> @@ -115,8 +116,9 @@ static int ttm_bo_vm_fault(struct vm_fault *vmf)
>>> unsigned long pfn;
>>> struct ttm_tt *ttm = NULL;
>>> struct page *page;
>>> - int ret;
>>> + int err;
>>> int i;
>>> + vm_fault_t ret = VM_FAULT_NOPAGE;
>>> unsigned long address = vmf->address;
>>> struct ttm_mem_type_manager *man =
>>> &bdev->man[bo->mem.mem_type];
>>> @@ -128,9 +130,9 @@ static int ttm_bo_vm_fault(struct vm_fault *vmf)
>>> * for reserve, and if it fails, retry the fault after waiting
>>> * for the buffer to become unreserved.
>>> */
>>> - ret = ttm_bo_reserve(bo, true, true, NULL);
>>> - if (unlikely(ret != 0)) {
>>> - if (ret != -EBUSY)
>>> + err = ttm_bo_reserve(bo, true, true, NULL);
>>> + if (unlikely(err != 0)) {
>>> + if (err != -EBUSY)
>>> return VM_FAULT_NOPAGE;
>>>
>>> if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
>>> @@ -162,8 +164,8 @@ static int ttm_bo_vm_fault(struct vm_fault *vmf)
>>> }
>>>
>>> if (bdev->driver->fault_reserve_notify) {
>>> - ret = bdev->driver->fault_reserve_notify(bo);
>>> - switch (ret) {
>>> + err = bdev->driver->fault_reserve_notify(bo);
>>> + switch (err) {
>>> case 0:
>>> break;
>>> case -EBUSY:
>>> @@ -191,13 +193,13 @@ static int ttm_bo_vm_fault(struct vm_fault *vmf)
>>> goto out_unlock;
>>> }
>>>
>>> - ret = ttm_mem_io_lock(man, true);
>>> - if (unlikely(ret != 0)) {
>>> + err = ttm_mem_io_lock(man, true);
>>> + if (unlikely(err != 0)) {
>>> ret = VM_FAULT_NOPAGE;
>>> goto out_unlock;
>>> }
>>> - ret = ttm_mem_io_reserve_vm(bo);
>>> - if (unlikely(ret != 0)) {
>>> + err = ttm_mem_io_reserve_vm(bo);
>>> + if (unlikely(err != 0)) {
>>> ret = VM_FAULT_SIGBUS;
>>> goto out_io_unlock;
>>> }
>>> @@ -265,23 +267,20 @@ static int ttm_bo_vm_fault(struct vm_fault *vmf)
>>> }
>>>
>>> if (vma->vm_flags & VM_MIXEDMAP)
>>> - ret = vm_insert_mixed(&cvma, address,
>>> + ret = vmf_insert_mixed(&cvma, address,
>>> __pfn_to_pfn_t(pfn, PFN_DEV));
>>> else
>>> - ret = vm_insert_pfn(&cvma, address, pfn);
>>> + ret = vmf_insert_pfn(&cvma, address, pfn);
>>>
>>> /*
>>> * Somebody beat us to this PTE or prefaulting to
>>> * an already populated PTE, or prefaulting error.
>>> */
>>>
>>> - if (unlikely((ret == -EBUSY) || (ret != 0 && i > 0)))
>>> + if (unlikely((ret == VM_FAULT_NOPAGE && i > 0)))
>>> break;
>>> - else if (unlikely(ret != 0)) {
>>> - ret =
>>> - (ret == -ENOMEM) ? VM_FAULT_OOM :
>>> VM_FAULT_SIGBUS;
>>> + else if (unlikely(ret & VM_FAULT_ERROR))
>>> goto out_io_unlock;
>>> - }
>>>
>>> address += PAGE_SIZE;
>>> if (unlikely(++page_offset >= page_last))
>>> --
>>> 1.9.1
>>>
>> If no further comment, we would like get this patch in 4.18 / 4.18-rc-x.
> The patch looks good to me and I will pick it up for the next TTM pull
> request. I don't think it will make it into 4.18-rc-1, but 4.18-rc-x
> sounds realistic.
The kernel is still compiling, but as soon as I know that this works I'm
going to push it into our internal branch which brings it on the way to
4.18-rc-2.
Regards,
Christian.
>
> Christian.
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