Message-ID: <20180420221346.GN1310@intel.com>
Date:   Fri, 20 Apr 2018 15:13:46 -0700
From:   Rodrigo Vivi <rodrigo.vivi@...el.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     Souptick Joarder <jrdr.linux@...il.com>,
        Matthew Wilcox <willy@...radead.org>, airlied@...ux.ie,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] gpu: drm: i915: Change return type to
 vm_fault_t

On Wed, Apr 18, 2018 at 08:46:44AM +0300, Jani Nikula wrote:
> On Tue, 17 Apr 2018, Souptick Joarder <jrdr.linux@...il.com> wrote:
> > On 17-Apr-2018 9:45 PM, "Matthew Wilcox" <willy@...radead.org> wrote:
> >>
> >> On Tue, Apr 17, 2018 at 09:14:32PM +0530, Souptick Joarder wrote:
> >> > Not exactly. The plan for these patches is to introduce new vm_fault_t
> > type
> >> > in vm_operations_struct fault handlers. It's now available in 4.17-rc1.
> > We will
> >> > push all the required drivers/filesystem changes through different
> > maintainers
> >> > to linus tree. Once everything is converted into vm_fault_t type then
> > Changing
> >> > it from a signed to an unsigned int causes GCC to warn about an
> > assignment
> >> > from an incompatible type -- int foo(void) is incompatible with
> >> > unsigned int foo(void).
> >> >
> >> > Please refer 1c8f422059ae ("mm: change return type to vm_fault_t") in
> > 4.17-rc1.
> >>
> >> I think this patch would be clearer if you did
> >>
> >> -       int ret;
> >> +       int err;
> >> +       vm_fault_t ret;
> >>
> >> Then it would be clearer to the maintainer that you're splitting apart the
> >> VM_FAULT and errno codes.
> >>
> >> Sorry for not catching this during initial review.
> >
> > Ok, I will make required changes and send v2. Sorry, even I missed this :)
> 
> I'm afraid Daniel is closer to the truth.

+1.

> My bad, sorry for the noise.

I opened this thread to add exactly question/noise ;).

So my recommendation for some next time is to make the intention clear
on the commit message itself from the begin.

> 
> BR,
> Jani.
> 
> 
> 
> >>
> >> > On Tue, Apr 17, 2018 at 8:59 PM, Jani Nikula
> >> > <jani.nikula@...ux.intel.com> wrote:
> >> > > On Tue, 17 Apr 2018, 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.
> >> > >>
> >> > >> Reference id -> 1c8f422059ae ("mm: change return type to
> >> > >> vm_fault_t")
> >> > >>
> >> > >> Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
> >> > >> ---
> >> > >>  drivers/gpu/drm/i915/i915_drv.h |  3 ++-
> >> > >>  drivers/gpu/drm/i915/i915_gem.c | 15 ++++++++-------
> >> > >>  2 files changed, 10 insertions(+), 8 deletions(-)
> >> > >>
> >> > >> diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > b/drivers/gpu/drm/i915/i915_drv.h
> >> > >> index a42deeb..95b0d50 100644
> >> > >> --- a/drivers/gpu/drm/i915/i915_drv.h
> >> > >> +++ b/drivers/gpu/drm/i915/i915_drv.h
> >> > >> @@ -51,6 +51,7 @@
> >> > >>  #include <drm/drm_gem.h>
> >> > >>  #include <drm/drm_auth.h>
> >> > >>  #include <drm/drm_cache.h>
> >> > >> +#include <linux/mm_types.h>
> >> > >>
> >> > >>  #include "i915_params.h"
> >> > >>  #include "i915_reg.h"
> >> > >> @@ -3363,7 +3364,7 @@ int i915_gem_wait_for_idle(struct
> > drm_i915_private *dev_priv,
> >> > >>                          unsigned int flags);
> >> > >>  int __must_check i915_gem_suspend(struct drm_i915_private
> > *dev_priv);
> >> > >>  void i915_gem_resume(struct drm_i915_private *dev_priv);
> >> > >> -int i915_gem_fault(struct vm_fault *vmf);
> >> > >> +vm_fault_t i915_gem_fault(struct vm_fault *vmf);
> >> > >>  int i915_gem_object_wait(struct drm_i915_gem_object *obj,
> >> > >>                        unsigned int flags,
> >> > >>                        long timeout,
> >> > >> diff --git a/drivers/gpu/drm/i915/i915_gem.c
> > b/drivers/gpu/drm/i915/i915_gem.c
> >> > >> index dd89abd..bdac690 100644
> >> > >> --- a/drivers/gpu/drm/i915/i915_gem.c
> >> > >> +++ b/drivers/gpu/drm/i915/i915_gem.c
> >> > >> @@ -1882,7 +1882,7 @@ int i915_gem_mmap_gtt_version(void)
> >> > >>   * The current feature set supported by i915_gem_fault() and thus
> > GTT mmaps
> >> > >>   * is exposed via I915_PARAM_MMAP_GTT_VERSION (see
> > i915_gem_mmap_gtt_version).
> >> > >>   */
> >> > >> -int i915_gem_fault(struct vm_fault *vmf)
> >> > >> +vm_fault_t i915_gem_fault(struct vm_fault *vmf)
> >> > >>  {
> >> > >>  #define MIN_CHUNK_PAGES ((1 << 20) >> PAGE_SHIFT) /* 1 MiB */
> >> > >>       struct vm_area_struct *area = vmf->vma;
> >> > >> @@ -1895,6 +1895,7 @@ int i915_gem_fault(struct vm_fault *vmf)
> >> > >>       pgoff_t page_offset;
> >> > >>       unsigned int flags;
> >> > >>       int ret;
> >> > >> +     vm_fault_t retval;
> >> > >
> >> > > What's the point of changing the name? An unnecessary change.
> >> > >
> >> > > BR,
> >> > > Jani.
> >> > >
> >> > >>
> >> > >>       /* We don't use vmf->pgoff since that has the fake offset */
> >> > >>       page_offset = (vmf->address - area->vm_start) >> PAGE_SHIFT;
> >> > >> @@ -2000,7 +2001,7 @@ int i915_gem_fault(struct vm_fault *vmf)
> >> > >>                * and so needs to be reported.
> >> > >>                */
> >> > >>               if (!i915_terminally_wedged(&dev_priv->gpu_error)) {
> >> > >> -                     ret = VM_FAULT_SIGBUS;
> >> > >> +                     retval = VM_FAULT_SIGBUS;
> >> > >>                       break;
> >> > >>               }
> >> > >>       case -EAGAIN:
> >> > >> @@ -2017,21 +2018,21 @@ int i915_gem_fault(struct vm_fault *vmf)
> >> > >>                * EBUSY is ok: this just means that another thread
> >> > >>                * already did the job.
> >> > >>                */
> >> > >> -             ret = VM_FAULT_NOPAGE;
> >> > >> +             retval = VM_FAULT_NOPAGE;
> >> > >>               break;
> >> > >>       case -ENOMEM:
> >> > >> -             ret = VM_FAULT_OOM;
> >> > >> +             retval = VM_FAULT_OOM;
> >> > >>               break;
> >> > >>       case -ENOSPC:
> >> > >>       case -EFAULT:
> >> > >> -             ret = VM_FAULT_SIGBUS;
> >> > >> +             retval = VM_FAULT_SIGBUS;
> >> > >>               break;
> >> > >>       default:
> >> > >>               WARN_ONCE(ret, "unhandled error in i915_gem_fault:
> > %i\n", ret);
> >> > >> -             ret = VM_FAULT_SIGBUS;
> >> > >> +             retval = VM_FAULT_SIGBUS;
> >> > >>               break;
> >> > >>       }
> >> > >> -     return ret;
> >> > >> +     return retval;
> >> > >>  }
> >> > >>
> >> > >>  static void __i915_gem_object_release_mmap(struct
> > drm_i915_gem_object *obj)
> >> > >> --
> >> > >> 1.9.1
> >> > >>
> >> > >
> >> > > --
> >> > > Jani Nikula, Intel Open Source Technology Center
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
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> Intel-gfx@...ts.freedesktop.org
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