drm/i915/ttm: Return some errors instead of trying memcpy move

The i915_ttm_accel_move() function may return error codes that should
be propagated further up the stack rather than consumed assuming that
the accel move failed and could be replaced with a memcpy move.

For -EINTR, -ERESTARTSYS and -EAGAIN, just propagate those codes, rather
than retrying with a memcpy move.

Fixes: 2b0a750caf ("drm/i915/ttm: Failsafe migration blits")
Cc: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220201070340.16457-1-thomas.hellstrom@linux.intel.com

drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c

@@ -436,11 +436,17 @@ __i915_ttm_move(struct ttm_buffer_object *bo,
 
 		if (!IS_ERR(fence))
 			goto out;
-	} else if (move_deps) {
-		int err = i915_deps_sync(move_deps, ctx);
+	} else {
+		int err = PTR_ERR(fence);
 
-		if (err)
-			return ERR_PTR(err);
+		if (err == -EINTR || err == -ERESTARTSYS || err == -EAGAIN)
+			return fence;
+
+		if (move_deps) {
+			err = i915_deps_sync(move_deps, ctx);
+			if (err)
+				return ERR_PTR(err);
+		}
 	}
 
 	/* Error intercept failed or no accelerated migration to start with */