drm/i915: fall through pwrite_gtt_slow to the shmem slow path

The gtt_pwrite slowpath grabs the userspace memory with
get_user_pages. This will not work for non-page backed memory, like a
gtt mmapped gem object. Hence fall throuh to the shmem paths if we hit
-EFAULT in the gtt paths.

Now the shmem paths have exactly the same problem, but this way we
only need to rearrange the code in one write path.

v2: v1 accidentaly falls back to shmem pwrite for phys objects. Fixed.

v3: Make the codeflow around phys_pwrite cleara as suggested by Chris
Wilson.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 21 insertions, 12 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index df23c6273413..7bb32ecc13c5 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -996,10 +996,13 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
          * pread/pwrite currently are reading and writing from the CPU
          * perspective, requiring manual detiling by the client.
          */
-        if (obj->phys_obj)
+        if (obj->phys_obj) {
                 ret = i915_gem_phys_pwrite(dev, obj, args, file);
-        else if (obj->gtt_space &&
-                 obj->base.write_domain != I915_GEM_DOMAIN_CPU) {
+                goto out;
+        }
+
+        if (obj->gtt_space &&
+            obj->base.write_domain != I915_GEM_DOMAIN_CPU) {
                 ret = i915_gem_object_pin(obj, 0, true);
                 if (ret)
                         goto out;
@@ -1018,18 +1021,24 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
 
 out_unpin:
                 i915_gem_object_unpin(obj);
-        } else {
-                ret = i915_gem_object_set_to_cpu_domain(obj, 1);
-                if (ret)
-                        goto out;
 
-                ret = -EFAULT;
-                if (!i915_gem_object_needs_bit17_swizzle(obj))
-                        ret = i915_gem_shmem_pwrite_fast(dev, obj, args, file);
-                if (ret == -EFAULT)
-                        ret = i915_gem_shmem_pwrite_slow(dev, obj, args, file);
+                if (ret != -EFAULT)
+                        goto out;
+                /* Fall through to the shmfs paths because the gtt paths might
+                 * fail with non-page-backed user pointers (e.g. gtt mappings
+                 * when moving data between textures). */
         }
 
+        ret = i915_gem_object_set_to_cpu_domain(obj, 1);
+        if (ret)
+                goto out;
+
+        ret = -EFAULT;
+        if (!i915_gem_object_needs_bit17_swizzle(obj))
+                ret = i915_gem_shmem_pwrite_fast(dev, obj, args, file);
+        if (ret == -EFAULT)
+                ret = i915_gem_shmem_pwrite_slow(dev, obj, args, file);
+
 out:
         drm_gem_object_unreference(&obj->base);
 unlock: