drm/gem: Consider GEM object reclaimable if shrinking fails

If the object wasn't moved to a different LRU after the shrink callback
returns, it means the buffer is still reclaimable. Update the remaining
counter to reflect that.

v2:
- Collect R-b

v3:
- Collect R-b

v4:
- No changes

v5:
- No changes

v6:
- No changes

v7:
- No changes

Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20260401134854.2275433-2-boris.brezillon@collabora.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

drivers/gpu/drm/drm_gem.c

@@ -1700,6 +1700,16 @@ drm_gem_lru_scan(struct drm_gem_lru *lru,
 			 */
 			WARN_ON(obj->lru == &still_in_lru);
 			WARN_ON(obj->lru == lru);
+		} else if (obj->lru == &still_in_lru) {
+			/*
+			 * If the object wasn't moved and wasn't shrunk either,
+			 * it's still remaining as reclaimable. Note that
+			 * obj->lru is supposed to be checked with the LRU lock
+			 * held for an accurate result, but we don't care about
+			 * accuracy here. Worst thing that could happen is an
+			 * extra scan.
+			 */
+			*remaining += obj->size >> PAGE_SHIFT;
 		}
 
 		dma_resv_unlock(obj->resv);