Re: [PATCH v2] gpu: drm: omapdrm: Adding new typedef vm_fault_t

[Souptick Joarder]

On Tue, May 22, 2018 at 11:43 PM, Souptick Joarder <jrdr.linux@xxxxxxxxx> 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() returns err which driver
> mapped into VM_FAULT_* type. Also return value of
> vm_insert_mixed() not handled correctly and 0 was
> returned inside fault_2d() as default. The new function
> vmf_insert_mixed() will replace this inefficiency by
> returning correct VM_FAULT_* type.
>
> vmf_error() is the newly introduce inline function
> in 4.17-rc6.
>
> Signed-off-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
> Reviewed-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
> ---
> v2: Fixed kbuild error by initialized ret
>     in fault_2d().
>
>  drivers/gpu/drm/omapdrm/omap_gem.c | 51 +++++++++++++++++---------------------
>  drivers/gpu/drm/omapdrm/omap_gem.h |  3 ++-
>  2 files changed, 25 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c
> index 0faf042..99e4300 100644
> --- a/drivers/gpu/drm/omapdrm/omap_gem.c
> +++ b/drivers/gpu/drm/omapdrm/omap_gem.c
> @@ -371,7 +371,7 @@ size_t omap_gem_mmap_size(struct drm_gem_object *obj)
>   */
>
>  /* Normal handling for the case of faulting in non-tiled buffers */
> -static int fault_1d(struct drm_gem_object *obj,
> +static vm_fault_t fault_1d(struct drm_gem_object *obj,
>                 struct vm_area_struct *vma, struct vm_fault *vmf)
>  {
>         struct omap_gem_object *omap_obj = to_omap_bo(obj);
> @@ -392,11 +392,12 @@ static int fault_1d(struct drm_gem_object *obj,
>         VERB("Inserting %p pfn %lx, pa %lx", (void *)vmf->address,
>                         pfn, pfn << PAGE_SHIFT);
>
> -       return vm_insert_mixed(vma, vmf->address, __pfn_to_pfn_t(pfn, PFN_DEV));
> +       return vmf_insert_mixed(vma, vmf->address,
> +                       __pfn_to_pfn_t(pfn, PFN_DEV));
>  }
>
>  /* Special handling for the case of faulting in 2d tiled buffers */
> -static int fault_2d(struct drm_gem_object *obj,
> +static vm_fault_t fault_2d(struct drm_gem_object *obj,
>                 struct vm_area_struct *vma, struct vm_fault *vmf)
>  {
>         struct omap_gem_object *omap_obj = to_omap_bo(obj);
> @@ -407,7 +408,8 @@ static int fault_2d(struct drm_gem_object *obj,
>         unsigned long pfn;
>         pgoff_t pgoff, base_pgoff;
>         unsigned long vaddr;
> -       int i, ret, slots;
> +       int i, err, slots;
> +       vm_fault_t ret = VM_FAULT_NOPAGE;
>
>         /*
>          * Note the height of the slot is also equal to the number of pages
> @@ -473,9 +475,10 @@ static int fault_2d(struct drm_gem_object *obj,
>         memset(pages + slots, 0,
>                         sizeof(struct page *) * (n - slots));
>
> -       ret = tiler_pin(entry->block, pages, ARRAY_SIZE(pages), 0, true);
> -       if (ret) {
> -               dev_err(obj->dev->dev, "failed to pin: %d\n", ret);
> +       err = tiler_pin(entry->block, pages, ARRAY_SIZE(pages), 0, true);
> +       if (err) {
> +               ret = vmf_error(err);
> +               dev_err(obj->dev->dev, "failed to pin: %d\n", err);
>                 return ret;
>         }
>
> @@ -485,7 +488,10 @@ static int fault_2d(struct drm_gem_object *obj,
>                         pfn, pfn << PAGE_SHIFT);
>
>         for (i = n; i > 0; i--) {
> -               vm_insert_mixed(vma, vaddr, __pfn_to_pfn_t(pfn, PFN_DEV));
> +               ret = vmf_insert_mixed(vma,
> +                       vaddr, __pfn_to_pfn_t(pfn, PFN_DEV));
> +               if (ret & VM_FAULT_ERROR)
> +                       break;
>                 pfn += priv->usergart[fmt].stride_pfn;
>                 vaddr += PAGE_SIZE * m;
>         }
> @@ -494,7 +500,7 @@ static int fault_2d(struct drm_gem_object *obj,
>         priv->usergart[fmt].last = (priv->usergart[fmt].last + 1)
>                                  % NUM_USERGART_ENTRIES;
>
> -       return 0;
> +       return ret;
>  }
>
>  /**
> @@ -509,14 +515,15 @@ static int fault_2d(struct drm_gem_object *obj,
>   * vma->vm_private_data points to the GEM object that is backing this
>   * mapping.
>   */
> -int omap_gem_fault(struct vm_fault *vmf)
> +vm_fault_t omap_gem_fault(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         struct drm_gem_object *obj = vma->vm_private_data;
>         struct omap_gem_object *omap_obj = to_omap_bo(obj);
>         struct drm_device *dev = obj->dev;
>         struct page **pages;
> -       int ret;
> +       int err;
> +       vm_fault_t ret;
>
>         /* Make sure we don't parallel update on a fault, nor move or remove
>          * something from beneath our feet
> @@ -524,9 +531,11 @@ int omap_gem_fault(struct vm_fault *vmf)
>         mutex_lock(&dev->struct_mutex);
>
>         /* if a shmem backed object, make sure we have pages attached now */
> -       ret = get_pages(obj, &pages);
> -       if (ret)
> +       err = get_pages(obj, &pages);
> +       if (err) {
> +               ret = vmf_error(err);
>                 goto fail;
> +       }
>
>         /* where should we do corresponding put_pages().. we are mapping
>          * the original page, rather than thru a GART, so we can't rely
> @@ -542,21 +551,7 @@ int omap_gem_fault(struct vm_fault *vmf)
>
>  fail:
>         mutex_unlock(&dev->struct_mutex);
> -       switch (ret) {
> -       case 0:
> -       case -ERESTARTSYS:
> -       case -EINTR:
> -       case -EBUSY:
> -               /*
> -                * EBUSY is ok: this just means that another thread
> -                * already did the job.
> -                */
> -               return VM_FAULT_NOPAGE;
> -       case -ENOMEM:
> -               return VM_FAULT_OOM;
> -       default:
> -               return VM_FAULT_SIGBUS;
> -       }
> +       return ret;
>  }
>
>  /** We override mainly to fix up some of the vm mapping flags.. */
> diff --git a/drivers/gpu/drm/omapdrm/omap_gem.h b/drivers/gpu/drm/omapdrm/omap_gem.h
> index a78bde0..c1c45fb 100644
> --- a/drivers/gpu/drm/omapdrm/omap_gem.h
> +++ b/drivers/gpu/drm/omapdrm/omap_gem.h
> @@ -21,6 +21,7 @@
>  #define __OMAPDRM_GEM_H__
>
>  #include <linux/types.h>
> +#include <linux/mm_types.h>
>
>  enum dma_data_direction;
>
> @@ -80,7 +81,7 @@ struct dma_buf *omap_gem_prime_export(struct drm_device *dev,
>  struct drm_gem_object *omap_gem_prime_import(struct drm_device *dev,
>                 struct dma_buf *buffer);
>
> -int omap_gem_fault(struct vm_fault *vmf);
> +vm_fault_t omap_gem_fault(struct vm_fault *vmf);
>  int omap_gem_roll(struct drm_gem_object *obj, u32 roll);
>  void omap_gem_cpu_sync_page(struct drm_gem_object *obj, int pgoff);
>  void omap_gem_dma_sync_buffer(struct drm_gem_object *obj,
> --
> 1.9.1
>

Any comment for this patch ? We would like to get this patch
in queue for 4.18.