linux-kernel - Re: [PATCH] gpu: drm: msm: Change return type to vm_fault

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Message-ID: <CAFqt6zY8VJ791_6C_pqrGgjG91T1kirEmUyA3JC+3JsN8QjFAw@mail.gmail.com>
Date:   Mon, 28 May 2018 12:38:41 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     Rob Clark <robdclark@...il.com>, airlied@...ux.ie,
        Matthew Wilcox <willy@...radead.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        freedreno@...ts.freedesktop.org
Subject: Re: [PATCH] gpu: drm: msm: Change return type to vm_fault_t

On Mon, May 21, 2018 at 10:59 PM, 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() returns err which driver
> mapped into VM_FAULT_* type. The new function
> vmf_insert_mixed() will replace this inefficiency by
> returning VM_FAULT_* type.
>
> vmf_error() is the newly introduce inline function
> in 4.17-rc6.
>
> Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
> Reviewed-by: Matthew Wilcox <mawilcox@...rosoft.com>
> ---
>  drivers/gpu/drm/msm/msm_drv.h |  3 ++-
>  drivers/gpu/drm/msm/msm_gem.c | 33 ++++++++++-----------------------
>  2 files changed, 12 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index 0a653dd..44b4ca7 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -33,6 +33,7 @@
>  #include <linux/of_graph.h>
>  #include <linux/of_device.h>
>  #include <asm/sizes.h>
> +#include <linux/mm_types.h>
>
>  #include <drm/drmP.h>
>  #include <drm/drm_atomic.h>
> @@ -188,7 +189,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
>  int msm_gem_mmap_obj(struct drm_gem_object *obj,
>                         struct vm_area_struct *vma);
>  int msm_gem_mmap(struct file *filp, struct vm_area_struct *vma);
> -int msm_gem_fault(struct vm_fault *vmf);
> +vm_fault_t msm_gem_fault(struct vm_fault *vmf);
>  uint64_t msm_gem_mmap_offset(struct drm_gem_object *obj);
>  int msm_gem_get_iova(struct drm_gem_object *obj,
>                 struct msm_gem_address_space *aspace, uint64_t *iova);
> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
> index 07376de..27a5ab5 100644
> --- a/drivers/gpu/drm/msm/msm_gem.c
> +++ b/drivers/gpu/drm/msm/msm_gem.c
> @@ -217,7 +217,7 @@ int msm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
>         return msm_gem_mmap_obj(vma->vm_private_data, vma);
>  }
>
> -int msm_gem_fault(struct vm_fault *vmf)
> +vm_fault_t msm_gem_fault(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         struct drm_gem_object *obj = vma->vm_private_data;
> @@ -225,15 +225,18 @@ int msm_gem_fault(struct vm_fault *vmf)
>         struct page **pages;
>         unsigned long pfn;
>         pgoff_t pgoff;
> -       int ret;
> +       int err;
> +       vm_fault_t ret;
>
>         /*
>          * vm_ops.open/drm_gem_mmap_obj and close get and put
>          * a reference on obj. So, we dont need to hold one here.
>          */
> -       ret = mutex_lock_interruptible(&msm_obj->lock);
> -       if (ret)
> +       err = mutex_lock_interruptible(&msm_obj->lock);
> +       if (err) {
> +               ret = VM_FAULT_NOPAGE;
>                 goto out;
> +       }
>
>         if (WARN_ON(msm_obj->madv != MSM_MADV_WILLNEED)) {
>                 mutex_unlock(&msm_obj->lock);
> @@ -243,7 +246,7 @@ int msm_gem_fault(struct vm_fault *vmf)
>         /* make sure we have pages attached now */
>         pages = get_pages(obj);
>         if (IS_ERR(pages)) {
> -               ret = PTR_ERR(pages);
> +               ret = vmf_error(PTR_ERR(pages));
>                 goto out_unlock;
>         }
>
> @@ -255,27 +258,11 @@ int msm_gem_fault(struct vm_fault *vmf)
>         VERB("Inserting %p pfn %lx, pa %lx", (void *)vmf->address,
>                         pfn, pfn << PAGE_SHIFT);
>
> -       ret = vm_insert_mixed(vma, vmf->address, __pfn_to_pfn_t(pfn, PFN_DEV));
> -
> +       ret = vmf_insert_mixed(vma, vmf->address, __pfn_to_pfn_t(pfn, PFN_DEV));
>  out_unlock:
>         mutex_unlock(&msm_obj->lock);
>  out:
> -       switch (ret) {
> -       case -EAGAIN:
> -       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;
>  }
>
>  /** get mmap offset */
> --
> 1.9.1
>

Any comment for this patch ?