In the continual quest to reduce the amount of global work required when
submitting requests, replace i915_retire_requests() after allocation
failure to retiring just our ring.

References: 11abf0c5a021 ("drm/i915: Limit the backpressure for i915_request 
allocation")
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
---
 drivers/gpu/drm/i915/i915_request.c | 33 +++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_request.c 
b/drivers/gpu/drm/i915/i915_request.c
index 1e158eb8cb97..9ba218c6029b 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -477,6 +477,29 @@ submit_notify(struct i915_sw_fence *fence, enum 
i915_sw_fence_notify state)
        return NOTIFY_DONE;
 }
 
+static noinline struct i915_request *
+i915_request_alloc_slow(struct intel_context *ce)
+{
+       struct intel_ring *ring = ce->ring;
+       struct i915_request *rq, *next;
+
+       list_for_each_entry_safe(rq, next, &ring->request_list, ring_link) {
+               /* Ratelimit ourselves to prevent oom from malicious clients */
+               if (&next->ring_link == &ring->request_list) {
+                       cond_synchronize_rcu(rq->rcustate);
+                       break; /* keep the last objects for the next request */
+               }
+
+               if (!i915_request_completed(rq))
+                       break;
+
+               /* Retire our old requests in the hope that we free some */
+               i915_request_retire(rq);
+       }
+
+       return kmem_cache_alloc(ce->gem_context->i915->requests, GFP_KERNEL);
+}
+
 /**
  * i915_request_alloc - allocate a request structure
  *
@@ -559,15 +582,7 @@ i915_request_alloc(struct intel_engine_cs *engine, struct 
i915_gem_context *ctx)
        rq = kmem_cache_alloc(i915->requests,
                              GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
        if (unlikely(!rq)) {
-               i915_retire_requests(i915);
-
-               /* Ratelimit ourselves to prevent oom from malicious clients */
-               rq = i915_gem_active_raw(&ce->ring->timeline->last_request,
-                                        &i915->drm.struct_mutex);
-               if (rq)
-                       cond_synchronize_rcu(rq->rcustate);
-
-               rq = kmem_cache_alloc(i915->requests, GFP_KERNEL);
+               rq = i915_request_alloc_slow(ce);
                if (!rq) {
                        ret = -ENOMEM;
                        goto err_unreserve;
-- 
2.20.1

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