[Intel-gfx] [PATCH 01/23] drm/i915: Drop vm.ref for duplicate vma on construction

[Chris Wilson]

As we allow for parallel threads to create vma instances in parallel,
and we only filter out the duplicates upon reacquiring the spinlock for
the rbtree, we have to free the loser of the constructors' race. When
freeing, we should also drop any resource references acquired for the
redundant vma.

Fixes: 2850748ef876 ("drm/i915: Pull i915_vma_pin under the vm->mutex")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: <stable at vger.kernel.org> # v5.5+
---
 drivers/gpu/drm/i915/i915_vma.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 1f63c4a1f055..7fe1f317cd2b 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -198,6 +198,7 @@ vma_create(struct drm_i915_gem_object *obj,
 		cmp = i915_vma_compare(pos, vm, view);
 		if (cmp == 0) {
 			spin_unlock(&obj->vma.lock);
+			i915_vm_put(vm);
 			i915_vma_free(vma);
 			return pos;
 		}
-- 
2.20.1