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Message-ID: <20180417161557.GA3603@bombadil.infradead.org>
Date: Tue, 17 Apr 2018 09:15:57 -0700
From: Matthew Wilcox <willy@...radead.org>
To: Souptick Joarder <jrdr.linux@...il.com>
Cc: Jani Nikula <jani.nikula@...ux.intel.com>,
joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com,
airlied@...ux.ie, intel-gfx@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpu: drm: i915: Change return type to vm_fault_t
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.
> 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
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