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

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Message-ID: <20180531175902.GC11565@jcrouse-lnx.qualcomm.com>
Date:   Thu, 31 May 2018 11:59:02 -0600
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     Souptick Joarder <jrdr.linux@...il.com>
Cc:     Rob Clark <robdclark@...il.com>, airlied@...ux.ie,
        Matthew Wilcox <willy@...radead.org>,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [Freedreno] [PATCH] gpu: drm: msm: Change return type to
 vm_fault_t

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@...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 ?

Sorry for the delay, I wanted to get a chance to test it. It seems to pass the
usual regression tests. LGTM.

Jordan

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