Re: [PATCH] gpu: drm: tegra: Adding new typedef vm_fault_t

[Thierry Reding]

On Tue, Apr 17, 2018 at 07:17:55PM +0530, Souptick Joarder 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.
> 
> Reference id -> 1c8f422059ae ("mm: change return type to
> vm_fault_t")
> 
> Previously vm_insert_page() returns err which driver
> mapped into VM_FAULT_* type. The new function 
> vmf_insert_page() will replace this inefficiency by
> returning VM_FAULT_* type.
> 
> Signed-off-by: Souptick Joarder 
> ---
>  drivers/gpu/drm/tegra/gem.c | 18 ++
>  1 file changed, 2 insertions(+), 16 deletions(-)

Applied, thanks.

Thierry


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Re: [PATCH] gpu: drm: tegra: Adding new typedef vm_fault_t

[Souptick Joarder]

On Mon, Apr 23, 2018 at 4:24 PM, Matthew Wilcox  wrote:
> On Wed, Apr 18, 2018 at 10:24:39AM +0200, Thierry Reding wrote:
>> > @@ -437,20 +436,7 @@ static int tegra_bo_fault(struct vm_fault *vmf)
>> > offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
>> > page = bo->pages[offset];
>> >
>> > -   err = vm_insert_page(vma, vmf->address, page);
>> > -   switch (err) {
>> > -   case -EAGAIN:
>> > -   case 0:
>> > -   case -ERESTARTSYS:
>> > -   case -EINTR:
>> > -   case -EBUSY:
>> > -   return VM_FAULT_NOPAGE;
>> > -
>> > -   case -ENOMEM:
>> > -   return VM_FAULT_OOM;
>> > -   }
>> > -
>> > -   return VM_FAULT_SIGBUS;
>> > +   return vmf_insert_page(vma, vmf->address, page);
>> >  }
>>
>> This new function returns VM_FAULT_NOPAGE only for 0 and -EBUSY, whereas
>> we used to return VM_FAULT_NOPAGE for -EAGAIN, -ERESTARTSYS and -EINTR
>> as well. Was this previously wrong?
>
> Not so much wrong as unnecessary.  vm_insert_page() can't return -EAGAIN,
> -ERESTARTSYS or -EINTR.

If no further comment on this patch, We would like to get this patch
queued for 4.18.
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Re: [PATCH] gpu: drm: tegra: Adding new typedef vm_fault_t

[Matthew Wilcox]

On Wed, Apr 18, 2018 at 10:24:39AM +0200, Thierry Reding wrote:
> > @@ -437,20 +436,7 @@ static int tegra_bo_fault(struct vm_fault *vmf)
> > offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
> > page = bo->pages[offset];
> > 
> > -   err = vm_insert_page(vma, vmf->address, page);
> > -   switch (err) {
> > -   case -EAGAIN:
> > -   case 0:
> > -   case -ERESTARTSYS:
> > -   case -EINTR:
> > -   case -EBUSY:
> > -   return VM_FAULT_NOPAGE;
> > -
> > -   case -ENOMEM:
> > -   return VM_FAULT_OOM;
> > -   }
> > -
> > -   return VM_FAULT_SIGBUS;
> > +   return vmf_insert_page(vma, vmf->address, page);
> >  }
> 
> This new function returns VM_FAULT_NOPAGE only for 0 and -EBUSY, whereas
> we used to return VM_FAULT_NOPAGE for -EAGAIN, -ERESTARTSYS and -EINTR
> as well. Was this previously wrong?

Not so much wrong as unnecessary.  vm_insert_page() can't return -EAGAIN,
-ERESTARTSYS or -EINTR.


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Re: [PATCH] gpu: drm: tegra: Adding new typedef vm_fault_t

[Souptick Joarder]

> This new function returns VM_FAULT_NOPAGE only for 0 and -EBUSY, whereas
> we used to return VM_FAULT_NOPAGE for -EAGAIN, -ERESTARTSYS and -EINTR
> as well.

Previously vm_insert_page unable to return VM_FAULT_ type due to which
different drivers
have their own mapping from err to VM_FAULT_ type. With new
vmf_insert_page() introduce
in 4.17-rc1 we have a common mapping for err to VM_FAULT_ which remain
same for every
drivers/file systems.

Was this previously wrong?

I think Matthew is the right person to answer this.
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Re: [PATCH] gpu: drm: tegra: Adding new typedef vm_fault_t

[Thierry Reding]

On Tue, Apr 17, 2018 at 07:17:55PM +0530, Souptick Joarder 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.
> 
> Reference id -> 1c8f422059ae ("mm: change return type to
> vm_fault_t")
> 
> Previously vm_insert_page() returns err which driver
> mapped into VM_FAULT_* type. The new function 
> vmf_insert_page() will replace this inefficiency by
> returning VM_FAULT_* type.
> 
> Signed-off-by: Souptick Joarder 
> ---
>  drivers/gpu/drm/tegra/gem.c | 18 ++
>  1 file changed, 2 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
> index 49b9bf2..6121493 100644
> --- a/drivers/gpu/drm/tegra/gem.c
> +++ b/drivers/gpu/drm/tegra/gem.c
> @@ -422,14 +422,13 @@ int tegra_bo_dumb_create(struct drm_file *file, struct 
> drm_device *drm,
>   return 0;
>  }
> 
> -static int tegra_bo_fault(struct vm_fault *vmf)
> +static vm_fault_t tegra_bo_fault(struct vm_fault *vmf)
>  {
>   struct vm_area_struct *vma = vmf->vma;
>   struct drm_gem_object *gem = vma->vm_private_data;
>   struct tegra_bo *bo = to_tegra_bo(gem);
>   struct page *page;
>   pgoff_t offset;
> - int err;
> 
>   if (!bo->pages)
>   return VM_FAULT_SIGBUS;
> @@ -437,20 +436,7 @@ static int tegra_bo_fault(struct vm_fault *vmf)
>   offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
>   page = bo->pages[offset];
> 
> - err = vm_insert_page(vma, vmf->address, page);
> - switch (err) {
> - case -EAGAIN:
> - case 0:
> - case -ERESTARTSYS:
> - case -EINTR:
> - case -EBUSY:
> - return VM_FAULT_NOPAGE;
> -
> - case -ENOMEM:
> - return VM_FAULT_OOM;
> - }
> -
> - return VM_FAULT_SIGBUS;
> + return vmf_insert_page(vma, vmf->address, page);
>  }

This new function returns VM_FAULT_NOPAGE only for 0 and -EBUSY, whereas
we used to return VM_FAULT_NOPAGE for -EAGAIN, -ERESTARTSYS and -EINTR
as well. Was this previously wrong?

Thierry


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[PATCH] gpu: drm: tegra: Adding new typedef vm_fault_t

[Souptick Joarder]

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.

Reference id -> 1c8f422059ae ("mm: change return type to
vm_fault_t")

Previously vm_insert_page() returns err which driver
mapped into VM_FAULT_* type. The new function 
vmf_insert_page() will replace this inefficiency by
returning VM_FAULT_* type.

Signed-off-by: Souptick Joarder 
---
 drivers/gpu/drm/tegra/gem.c | 18 ++
 1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
index 49b9bf2..6121493 100644
--- a/drivers/gpu/drm/tegra/gem.c
+++ b/drivers/gpu/drm/tegra/gem.c
@@ -422,14 +422,13 @@ int tegra_bo_dumb_create(struct drm_file *file, struct 
drm_device *drm,
return 0;
 }

-static int tegra_bo_fault(struct vm_fault *vmf)
+static vm_fault_t tegra_bo_fault(struct vm_fault *vmf)
 {
struct vm_area_struct *vma = vmf->vma;
struct drm_gem_object *gem = vma->vm_private_data;
struct tegra_bo *bo = to_tegra_bo(gem);
struct page *page;
pgoff_t offset;
-   int err;

if (!bo->pages)
return VM_FAULT_SIGBUS;
@@ -437,20 +436,7 @@ static int tegra_bo_fault(struct vm_fault *vmf)
offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
page = bo->pages[offset];

-   err = vm_insert_page(vma, vmf->address, page);
-   switch (err) {
-   case -EAGAIN:
-   case 0:
-   case -ERESTARTSYS:
-   case -EINTR:
-   case -EBUSY:
-   return VM_FAULT_NOPAGE;
-
-   case -ENOMEM:
-   return VM_FAULT_OOM;
-   }
-
-   return VM_FAULT_SIGBUS;
+   return vmf_insert_page(vma, vmf->address, page);
 }

 const struct vm_operations_struct tegra_bo_vm_ops = {
--
1.9.1

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[PATCH] gpu: drm: tegra: Adding new typedef vm_fault_t

[Souptick Joarder]

Use new return type vm_fault_t for fault handler
in vm_operations_struct.

Signed-off-by: Souptick Joarder 
---
 drivers/gpu/drm/tegra/gem.c | 18 ++
 1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
index 49b9bf2..6121493 100644
--- a/drivers/gpu/drm/tegra/gem.c
+++ b/drivers/gpu/drm/tegra/gem.c
@@ -422,14 +422,13 @@ int tegra_bo_dumb_create(struct drm_file *file, struct 
drm_device *drm,
return 0;
 }

-static int tegra_bo_fault(struct vm_fault *vmf)
+static vm_fault_t tegra_bo_fault(struct vm_fault *vmf)
 {
struct vm_area_struct *vma = vmf->vma;
struct drm_gem_object *gem = vma->vm_private_data;
struct tegra_bo *bo = to_tegra_bo(gem);
struct page *page;
pgoff_t offset;
-   int err;

if (!bo->pages)
return VM_FAULT_SIGBUS;
@@ -437,20 +436,7 @@ static int tegra_bo_fault(struct vm_fault *vmf)
offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
page = bo->pages[offset];

-   err = vm_insert_page(vma, vmf->address, page);
-   switch (err) {
-   case -EAGAIN:
-   case 0:
-   case -ERESTARTSYS:
-   case -EINTR:
-   case -EBUSY:
-   return VM_FAULT_NOPAGE;
-
-   case -ENOMEM:
-   return VM_FAULT_OOM;
-   }
-
-   return VM_FAULT_SIGBUS;
+   return vmf_insert_page(vma, vmf->address, page);
 }

 const struct vm_operations_struct tegra_bo_vm_ops = {
--
1.9.1

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