From 4bda375a330b1c741aa827d04b24889a50121d79 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 2 Jul 2020 09:32:03 +0100
Subject: drm/i915: Drop vm.ref for duplicate vma on construction
Git-commit: 42723673a193d5f8e30dba6ea9826d42262a502b
Patch-mainline: v5.8-rc5
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322

As we allow for parallel threads to create the same vma instance
concurrently, 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@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: <stable@vger.kernel.org> # v5.5+
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200702083225.20044-1-chris@chris-wilson.co.uk
(cherry picked from commit 2377427cdd2b7514eb4c40241cf5c4dec63c1bec)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 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 fc14ebf9a0b7..2d60fd1f3637 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;
 		}
-- 
2.28.0