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, 8 insertions, 7 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 53de95c05b1..04b0c070cdf 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1956,11 +1956,12 @@ i915_gem_next_request_seqno(struct intel_ring_buffer *ring)
 int
 i915_add_request(struct intel_ring_buffer *ring,
 		 struct drm_file *file,
-		 struct drm_i915_gem_request *request)
+		 u32 *out_seqno)
 {
 	drm_i915_private_t *dev_priv = ring->dev->dev_private;
-	uint32_t seqno;
+	struct drm_i915_gem_request *request;
 	u32 request_ring_position;
+	u32 seqno;
 	int was_empty;
 	int ret;
 
@@ -1975,11 +1976,9 @@ i915_add_request(struct intel_ring_buffer *ring,
 	if (ret)
 		return ret;
 
-	if (request == NULL) {
-		request = kmalloc(sizeof(*request), GFP_KERNEL);
-		if (request == NULL)
-			return -ENOMEM;
-	}
+	request = kmalloc(sizeof(*request), GFP_KERNEL);
+	if (request == NULL)
+		return -ENOMEM;
 
 	seqno = i915_gem_next_request_seqno(ring);
 
@@ -2031,6 +2030,8 @@ i915_add_request(struct intel_ring_buffer *ring,
 		}
 	}
 
+	if (out_seqno)
+		*out_seqno = seqno;
 	return 0;
 }