[Intel-gfx] [PATCH 2/3] drm/i915: Allow fence allocations to fail

[Chris Wilson]

If a fence allocation fails in a blocking context, we will sleep on the
fence as a last resort. We can therefore allow ourselves to fail and
sleep on the fence instead of triggering a system-wide oom. This allows
us to throttle malicious clients that are consuming lots of system
resources by capping the amount of memory used by fences.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem_clflush.c | 2 +-
 drivers/gpu/drm/i915/i915_gem_context.c | 2 +-
 drivers/gpu/drm/i915/i915_gem_request.c | 6 +++---
 drivers/gpu/drm/i915/i915_gem_request.h | 2 ++
 4 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_clflush.c b/drivers/gpu/drm/i915/i915_gem_clflush.c
index f663cd919795..b9b53ac14176 100644
--- a/drivers/gpu/drm/i915/i915_gem_clflush.c
+++ b/drivers/gpu/drm/i915/i915_gem_clflush.c
@@ -167,7 +167,7 @@ bool i915_gem_clflush_object(struct drm_i915_gem_object *obj,
 		i915_sw_fence_await_reservation(&clflush->wait,
 						obj->resv, NULL,
 						true, I915_FENCE_TIMEOUT,
-						GFP_KERNEL);
+						I915_FENCE_GFP);
 
 		reservation_object_lock(obj->resv, NULL);
 		reservation_object_add_excl_fence(obj->resv, &clflush->dma);
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 21ce374d9924..648e7536ff51 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -617,7 +617,7 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
 			if (prev)
 				i915_sw_fence_await_sw_fence_gfp(&req->submit,
 								 &prev->submit,
-								 GFP_KERNEL);
+								 I915_FENCE_GFP);
 		}
 
 		/*
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index c28a4ceb016d..4d5e2b714382 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -782,7 +782,7 @@ i915_gem_request_await_request(struct drm_i915_gem_request *to,
 	if (to->engine == from->engine) {
 		ret = i915_sw_fence_await_sw_fence_gfp(&to->submit,
 						       &from->submit,
-						       GFP_KERNEL);
+						       I915_FENCE_GFP);
 		return ret < 0 ? ret : 0;
 	}
 
@@ -810,7 +810,7 @@ i915_gem_request_await_request(struct drm_i915_gem_request *to,
 await_dma_fence:
 	ret = i915_sw_fence_await_dma_fence(&to->submit,
 					    &from->fence, 0,
-					    GFP_KERNEL);
+					    I915_FENCE_GFP);
 	return ret < 0 ? ret : 0;
 }
 
@@ -861,7 +861,7 @@ i915_gem_request_await_dma_fence(struct drm_i915_gem_request *req,
 		else
 			ret = i915_sw_fence_await_dma_fence(&req->submit, fence,
 							    I915_FENCE_TIMEOUT,
-							    GFP_KERNEL);
+							    I915_FENCE_GFP);
 		if (ret < 0)
 			return ret;
 
diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h
index 26249f39de67..0d6d39f19506 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.h
+++ b/drivers/gpu/drm/i915/i915_gem_request.h
@@ -204,6 +204,8 @@ struct drm_i915_gem_request {
 	struct list_head client_link;
 };
 
+#define I915_FENCE_GFP (GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN)
+
 extern const struct dma_fence_ops i915_fence_ops;
 
 static inline bool dma_fence_is_i915(const struct dma_fence *fence)
-- 
2.15.1