drm/i915: Disallow preallocation of requests

The intention was to allow the caller to avoid a failure to queue a
request having already written commands to the ring. However, this is a
moot point as the i915_add_request() can fail for other reasons than a
mere allocation failure and those failure cases are more likely than
ENOMEM. So the overlay code already had to handle i915_add_request()
failures, and due to

commit 3bb73aba1ed5198a2c1dfaac4f3c95459930d84a
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Jul 20 12:40:59 2012 +0100

    drm/i915: Allow late allocation of request for i915_add_request()

the error handling code in intel_overlay.c was subject to causing
double-frees, as found by coverity.

Rather than further complicate i915_add_request() and callers, realise
the battle is lost and adapt intel_overlay.c to take advantage of the
late allocation of requests.

v2: Handle callers passing in a NULL seqno.
v3: Ditto. This time for sure.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 15 insertions, 57 deletions

diff --git a/drivers/gpu/drm/i915/intel_overlay.c b/drivers/gpu/drm/i915/intel_overlay.c
index afd0f30ab882..555912f510a9 100644
--- a/drivers/gpu/drm/i915/intel_overlay.c
+++ b/drivers/gpu/drm/i915/intel_overlay.c
@@ -210,7 +210,6 @@ static void intel_overlay_unmap_regs(struct intel_overlay *overlay,
 }
 
 static int intel_overlay_do_wait_request(struct intel_overlay *overlay,
-                                         struct drm_i915_gem_request *request,
                                          void (*tail)(struct intel_overlay *))
 {
         struct drm_device *dev = overlay->dev;
@@ -219,12 +218,10 @@ static int intel_overlay_do_wait_request(struct intel_overlay *overlay,
         int ret;
 
         BUG_ON(overlay->last_flip_req);
-        ret = i915_add_request(ring, NULL, request);
-        if (ret) {
-            kfree(request);
-            return ret;
-        }
-        overlay->last_flip_req = request->seqno;
+        ret = i915_add_request(ring, NULL, &overlay->last_flip_req);
+        if (ret)
+                return ret;
+
         overlay->flip_tail = tail;
         ret = i915_wait_seqno(ring, overlay->last_flip_req);
         if (ret)
@@ -241,7 +238,6 @@ static int intel_overlay_on(struct intel_overlay *overlay)
         struct drm_device *dev = overlay->dev;
         struct drm_i915_private *dev_priv = dev->dev_private;
         struct intel_ring_buffer *ring = &dev_priv->ring[RCS];
-        struct drm_i915_gem_request *request;
         int ret;
 
         BUG_ON(overlay->active);
@@ -249,17 +245,9 @@ static int intel_overlay_on(struct intel_overlay *overlay)
 
         WARN_ON(IS_I830(dev) && !(dev_priv->quirks & QUIRK_PIPEA_FORCE));
 
-        request = kzalloc(sizeof(*request), GFP_KERNEL);
-        if (request == NULL) {
-                ret = -ENOMEM;
-                goto out;
-        }
-
         ret = intel_ring_begin(ring, 4);
-        if (ret) {
-                kfree(request);
-                goto out;
-        }
+        if (ret)
+                return ret;
 
         intel_ring_emit(ring, MI_OVERLAY_FLIP | MI_OVERLAY_ON);
         intel_ring_emit(ring, overlay->flip_addr | OFC_UPDATE);
@@ -267,9 +255,7 @@ static int intel_overlay_on(struct intel_overlay *overlay)
         intel_ring_emit(ring, MI_NOOP);
         intel_ring_advance(ring);
 
-        ret = intel_overlay_do_wait_request(overlay, request, NULL);
-out:
-        return ret;
+        return intel_overlay_do_wait_request(overlay, NULL);
 }
 
 /* overlay needs to be enabled in OCMD reg */
@@ -279,17 +265,12 @@ static int intel_overlay_continue(struct intel_overlay *overlay,
         struct drm_device *dev = overlay->dev;
         drm_i915_private_t *dev_priv = dev->dev_private;
         struct intel_ring_buffer *ring = &dev_priv->ring[RCS];
-        struct drm_i915_gem_request *request;
         u32 flip_addr = overlay->flip_addr;
         u32 tmp;
         int ret;
 
         BUG_ON(!overlay->active);
 
-        request = kzalloc(sizeof(*request), GFP_KERNEL);
-        if (request == NULL)
-                return -ENOMEM;
-
         if (load_polyphase_filter)
                 flip_addr |= OFC_UPDATE;
 
@@ -299,22 +280,14 @@ static int intel_overlay_continue(struct intel_overlay *overlay,
                 DRM_DEBUG("overlay underrun, DOVSTA: %x\n", tmp);
 
         ret = intel_ring_begin(ring, 2);
-        if (ret) {
-                kfree(request);
+        if (ret)
                 return ret;
-        }
+
         intel_ring_emit(ring, MI_OVERLAY_FLIP | MI_OVERLAY_CONTINUE);
         intel_ring_emit(ring, flip_addr);
         intel_ring_advance(ring);
 
-        ret = i915_add_request(ring, NULL, request);
-        if (ret) {
-                kfree(request);
-                return ret;
-        }
-
-        overlay->last_flip_req = request->seqno;
-        return 0;
+        return i915_add_request(ring, NULL, &overlay->last_flip_req);
 }
 
 static void intel_overlay_release_old_vid_tail(struct intel_overlay *overlay)
@@ -350,15 +323,10 @@ static int intel_overlay_off(struct intel_overlay *overlay)
         struct drm_i915_private *dev_priv = dev->dev_private;
         struct intel_ring_buffer *ring = &dev_priv->ring[RCS];
         u32 flip_addr = overlay->flip_addr;
-        struct drm_i915_gem_request *request;
         int ret;
 
         BUG_ON(!overlay->active);
 
-        request = kzalloc(sizeof(*request), GFP_KERNEL);
-        if (request == NULL)
-                return -ENOMEM;
-
         /* According to intel docs the overlay hw may hang (when switching
          * off) without loading the filter coeffs. It is however unclear whether
          * this applies to the disabling of the overlay or to the switching off
@@ -366,10 +334,9 @@ static int intel_overlay_off(struct intel_overlay *overlay)
         flip_addr |= OFC_UPDATE;
 
         ret = intel_ring_begin(ring, 6);
-        if (ret) {
-                kfree(request);
+        if (ret)
                 return ret;
-        }
+
         /* wait for overlay to go idle */
         intel_ring_emit(ring, MI_OVERLAY_FLIP | MI_OVERLAY_CONTINUE);
         intel_ring_emit(ring, flip_addr);
@@ -380,8 +347,7 @@ static int intel_overlay_off(struct intel_overlay *overlay)
         intel_ring_emit(ring, MI_WAIT_FOR_EVENT | MI_WAIT_FOR_OVERLAY_FLIP);
         intel_ring_advance(ring);
 
-        return intel_overlay_do_wait_request(overlay, request,
-                                             intel_overlay_off_tail);
+        return intel_overlay_do_wait_request(overlay, intel_overlay_off_tail);
 }
 
 /* recover from an interruption due to a signal
@@ -426,24 +392,16 @@ static int intel_overlay_release_old_vid(struct intel_overlay *overlay)
                 return 0;
 
         if (I915_READ(ISR) & I915_OVERLAY_PLANE_FLIP_PENDING_INTERRUPT) {
-                struct drm_i915_gem_request *request;
-
                 /* synchronous slowpath */
-                request = kzalloc(sizeof(*request), GFP_KERNEL);
-                if (request == NULL)
-                        return -ENOMEM;
-
                 ret = intel_ring_begin(ring, 2);
-                if (ret) {
-                        kfree(request);
+                if (ret)
                         return ret;
-                }
 
                 intel_ring_emit(ring, MI_WAIT_FOR_EVENT | MI_WAIT_FOR_OVERLAY_FLIP);
                 intel_ring_emit(ring, MI_NOOP);
                 intel_ring_advance(ring);
 
-                ret = intel_overlay_do_wait_request(overlay, request,
+                ret = intel_overlay_do_wait_request(overlay,
                                                     intel_overlay_release_old_vid_tail);
                 if (ret)
                         return ret;