Re: [PATCH] gpu: drm: msm: Change return type to vm_fault_t

[Souptick Joarder <jrdr.linux-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Thu, May 31, 2018 at 11:29 PM, Jordan Crouse <jcrouse@codeaurora.org> wrote:
> On Mon, May 28, 2018 at 12:38:41PM +0530, Souptick Joarder wrote:
>> On Mon, May 21, 2018 at 10:59 PM, Souptick Joarder <jrdr.linux@gmail.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@gmail.com>
>> > Reviewed-by: Matthew Wilcox <mawilcox@microsoft.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 ?
>
> Sorry for the delay, I wanted to get a chance to test it. It seems to pass the
> usual regression tests. LGTM.
>

Jordan, This patch is not merged in 4.18-rc-1.
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