[PATCH v2 4/4] drm/ttm: Allow continued swapout after -ENOSPC falure

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

The -ENOSPC failure from ttm_bo_swapout() meant that the lru_lock
was dropped and simply restarting the iteration meant we'd likely
hit the same error again on the same resource. Now that we can
restart the iteration even if the lock was dropped, do that.

Cc: Christian König <christian.koenig@amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_device.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index e8a6a1dab669..4a030b4bc848 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -168,15 +168,20 @@ int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
 
 			num_pages = PFN_UP(bo->base.size);
 			ret = ttm_bo_swapout(bo, ctx, gfp_flags);
-			/* ttm_bo_swapout has dropped the lru_lock */
-			if (!ret) {
-				ttm_resource_cursor_fini(&cursor);
-				return num_pages;
-			}
-			if (ret != -EBUSY) {
-				ttm_resource_cursor_fini(&cursor);
-				return ret;
+			/* Couldn't swap out, and retained the lru_lock */
+			if (ret == -EBUSY)
+				continue;
+			/* Couldn't swap out and dropped the lru_lock */
+			if (ret == -ENOSPC) {
+				spin_lock(&bdev->lru_lock);
+				continue;
 			}
+			/*
+			 * Dropped the lock and either succeeded or
+			 * hit an error that forces us to break.
+			 */
+			ttm_resource_cursor_fini(&cursor);
+			return ret ? ret : num_pages;
 		}
 	}
 	ttm_resource_cursor_fini_locked(&cursor);
-- 
2.44.0