[PATCH 08/16] drm/i915: Change shrink ordering to use locking around unbinding.

[Maarten Lankhorst]

Call drop_pages with the gem object lock held, instead of the other
way around. This will allow us to drop the vma bindings with the
gem object lock held.

We plan to require the object lock for unpinning in the future,
and this is an easy target.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_shrinker.c | 50 ++++++++++----------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
index 09465f2c1d69..7ae1f4c00516 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
@@ -37,8 +37,8 @@ static bool can_release_pages(struct drm_i915_gem_object *obj)
 	return swap_available() || obj->mm.madv == I915_MADV_DONTNEED;
 }
 
-static bool unsafe_drop_pages(struct drm_i915_gem_object *obj,
-			      unsigned long shrink, bool trylock_vm)
+static int drop_pages(struct drm_i915_gem_object *obj,
+		       unsigned long shrink, bool trylock_vm)
 {
 	unsigned long flags;
 
@@ -50,10 +50,7 @@ static bool unsafe_drop_pages(struct drm_i915_gem_object *obj,
 	if (trylock_vm)
 		flags |= I915_GEM_OBJECT_UNBIND_VM_TRYLOCK;
 
-	if (i915_gem_object_unbind(obj, flags) == 0)
-		return true;
-
-	return false;
+	return i915_gem_object_unbind(obj, flags);
 }
 
 static void try_to_writeback(struct drm_i915_gem_object *obj,
@@ -209,29 +206,32 @@ i915_gem_shrink(struct i915_gem_ww_ctx *ww,
 
 			spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 
+			/* May arrive from get_pages on another bo */
 			err = 0;
-			if (unsafe_drop_pages(obj, shrink, trylock_vm)) {
-				/* May arrive from get_pages on another bo */
-				if (!ww) {
-					if (!i915_gem_object_trylock(obj))
-						goto skip;
-				} else {
-					err = i915_gem_object_lock(obj, ww);
-					if (err)
-						goto skip;
-				}
-
-				if (!__i915_gem_object_put_pages(obj)) {
-					try_to_writeback(obj, shrink);
-					count += obj->base.size >> PAGE_SHIFT;
-				}
-				if (!ww)
-					i915_gem_object_unlock(obj);
+			if (!ww) {
+				if (!i915_gem_object_trylock(obj))
+					goto skip;
+			} else {
+				err = i915_gem_object_lock(obj, ww);
+				if (err)
+					goto skip;
+			}
+
+			err = drop_pages(obj, shrink, trylock_vm);
+			if (!err && !__i915_gem_object_put_pages(obj)) {
+				try_to_writeback(obj, shrink);
+				count += obj->base.size >> PAGE_SHIFT;
 			}
 
-			dma_resv_prune(obj->base.resv);
+			if (dma_resv_test_signaled(obj->base.resv, true))
+				dma_resv_add_excl_fence(obj->base.resv, NULL);
+
+			if (!ww)
+				i915_gem_object_unlock(obj);
+
+			if (!err)
+				scanned += obj->base.size >> PAGE_SHIFT;
 
-			scanned += obj->base.size >> PAGE_SHIFT;
 skip:
 			i915_gem_object_put(obj);
 
-- 
2.31.0