[PATCH 11/21] drm/i915: Stop manually RCU banging in reset_stats_ioctl

[Jason Ekstrand]

As far as I can tell, the only real reason for this is to avoid taking a
reference to the i915_gem_context.  The cost of those two atomics
probably pales in comparison to the cost of the ioctl itself so we're
really not buying ourselves anything here.  We're about to make context
lookup a tiny bit more complicated, so let's get rid of the one hand-
rolled case.

Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
---
 drivers/gpu/drm/i915/gem/i915_gem_context.c | 13 ++++---------
 drivers/gpu/drm/i915/i915_drv.h             |  8 +-------
 2 files changed, 5 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index ecb3bf5369857..941fbf78267b4 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -2090,16 +2090,13 @@ int i915_gem_context_reset_stats_ioctl(struct drm_device *dev,
 	struct drm_i915_private *i915 = to_i915(dev);
 	struct drm_i915_reset_stats *args = data;
 	struct i915_gem_context *ctx;
-	int ret;
 
 	if (args->flags || args->pad)
 		return -EINVAL;
 
-	ret = -ENOENT;
-	rcu_read_lock();
-	ctx = __i915_gem_context_lookup_rcu(file->driver_priv, args->ctx_id);
+	ctx = i915_gem_context_lookup(file->driver_priv, args->ctx_id);
 	if (!ctx)
-		goto out;
+		return -ENOENT;
 
 	/*
 	 * We opt for unserialised reads here. This may result in tearing
@@ -2116,10 +2113,8 @@ int i915_gem_context_reset_stats_ioctl(struct drm_device *dev,
 	args->batch_active = atomic_read(&ctx->guilty_count);
 	args->batch_pending = atomic_read(&ctx->active_count);
 
-	ret = 0;
-out:
-	rcu_read_unlock();
-	return ret;
+	i915_gem_context_put(ctx);
+	return 0;
 }
 
 /* GEM context-engines iterator: for_each_gem_engine() */
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 0b44333eb7033..8571c5c1509a7 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1840,19 +1840,13 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
 
 struct dma_buf *i915_gem_prime_export(struct drm_gem_object *gem_obj, int flags);
 
-static inline struct i915_gem_context *
-__i915_gem_context_lookup_rcu(struct drm_i915_file_private *file_priv, u32 id)
-{
-	return xa_load(&file_priv->context_xa, id);
-}
-
 static inline struct i915_gem_context *
 i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id)
 {
 	struct i915_gem_context *ctx;
 
 	rcu_read_lock();
-	ctx = __i915_gem_context_lookup_rcu(file_priv, id);
+	ctx = xa_load(&file_priv->context_xa, id);
 	if (ctx && !kref_get_unless_zero(&ctx->ref))
 		ctx = NULL;
 	rcu_read_unlock();
-- 
2.31.1