[Intel-gfx] [RFC 2/5] drm/i915: Extract code mapping errno to vm fault code

[Chris Wilson]

On Tue, Jan 26, 2016 at 04:24:46PM +0000, Tvrtko Ursulin wrote:
> 
> 
> On 26/01/16 15:18, Chris Wilson wrote:
> >On Tue, Jan 26, 2016 at 02:53:30PM +0000, Tvrtko Ursulin wrote:
> >>From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>
> >>Will be used from multiple callers in a following patch.
> >>
> >>Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>---
> >>  drivers/gpu/drm/i915/i915_gem.c | 91 ++++++++++++++++++++++-------------------
> >>  1 file changed, 49 insertions(+), 42 deletions(-)
> >>
> >>diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> >>index af15c290c71d..dacf6a0013c5 100644
> >>--- a/drivers/gpu/drm/i915/i915_gem.c
> >>+++ b/drivers/gpu/drm/i915/i915_gem.c
> >>@@ -1772,6 +1772,53 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
> >>  	return 0;
> >>  }
> >>
> >>+static int
> >>+i915_gem_ret_to_vm_ret(struct drm_i915_private *dev_priv, int ret)
> >>+{
> >>+	switch (ret) {
> >>+	case -EIO:
> >>+		/*
> >>+		 * We eat errors when the gpu is terminally wedged to avoid
> >>+		 * userspace unduly crashing (gl has no provisions for mmaps to
> >>+		 * fail). But any other -EIO isn't ours (e.g. swap in failure)
> >>+		 * and so needs to be reported.
> >>+		 */
> >>+		if (!i915_terminally_wedged(&dev_priv->gpu_error)) {
> >>+			ret = VM_FAULT_SIGBUS;
> >>+			break;
> >>+		}
> >>+	case -EAGAIN:
> >>+		/*
> >>+		 * EAGAIN means the gpu is hung and we'll wait for the error
> >>+		 * handler to reset everything when re-faulting in
> >>+		 * i915_mutex_lock_interruptible.
> >>+		 */
> >>+	case 0:
> >>+	case -ERESTARTSYS:
> >>+	case -EINTR:
> >>+	case -EBUSY:
> >>+		/*
> >>+		 * EBUSY is ok: this just means that another thread
> >>+		 * already did the job.
> >>+		 */
> >>+		ret = VM_FAULT_NOPAGE;
> >>+		break;
> >>+	case -ENOMEM:
> >>+		ret = VM_FAULT_OOM;
> >>+		break;
> >>+	case -ENOSPC:
> >>+	case -EFAULT:
> >>+		ret = VM_FAULT_SIGBUS;
> >>+		break;
> >>+	default:
> >>+		WARN_ONCE(ret, "unhandled error in page fault\n");
> >>+		ret = VM_FAULT_SIGBUS;
> >>+		break;
> >>+	}
> >
> >So without having to pin (plus a few other similar changes), we only need
> >to report
> >
> >-ENOMEM, -ENOSPC, -EIO (from shmemfs) and -EFAULT (get_pages).
> >
> >Given that I'd rather have the reasoning behind each explicit.
> 
> This is just existing code factored out so I am not sure what you
> are suggesting?

I'm looking at the next user and wondering how many of these comments
should (and do) apply.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre