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From:   Jani Nikula <jani.nikula@linux.intel.com>
To:     Souptick Joarder <jrdr.linux@gmail.com>,
        Matthew Wilcox <willy@infradead.org>
Cc:     rodrigo.vivi@intel.com, linux-kernel@vger.kernel.org,
        joonas.lahtinen@linux.intel.com, intel-gfx@lists.freedesktop.org,
        airlied@linux.ie, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] gpu: drm: i915: Change return type to vm_fault_t
In-Reply-To: <CAFqt6zb5TgZEHHT9kTWsoQ8REy6rVjZ6uQN4oQ2LUatwG13jQw@mail.gmail.com>
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
References: <20180417151127.GA31655@jordon-HP-15-Notebook-PC> <87h8o9g8be.fsf@intel.com> <CAFqt6zb_XqVKHPH5U4TubgDTgBURWv63cfa_OMQEyHjGZpKTHQ@mail.gmail.com> <20180417161557.GA3603@bombadil.infradead.org> <CAFqt6zb5TgZEHHT9kTWsoQ8REy6rVjZ6uQN4oQ2LUatwG13jQw@mail.gmail.com>
Date:   Wed, 18 Apr 2018 08:46:44 +0300
Message-ID: <871sfdxe0r.fsf@intel.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
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On Tue, 17 Apr 2018, Souptick Joarder <jrdr.linux@gmail.com> wrote:
> On 17-Apr-2018 9:45 PM, "Matthew Wilcox" <willy@infradead.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. My bad, sorry for the noise.

BR,
Jani.


>>
>> > On Tue, Apr 17, 2018 at 8:59 PM, Jani Nikula
>> > <jani.nikula@linux.intel.com> wrote:
>> > > On Tue, 17 Apr 2018, 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.
>> > >>
>> > >> Reference id -> 1c8f422059ae ("mm: change return type to
>> > >> vm_fault_t")
>> > >>
>> > >> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.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