swiotlb: make swiotlb_exit a no-op if SWIOTLB_FORCE is set

If force bouncing is enabled we can't release the buffers.

Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Anshuman Khandual <[email protected]>
Reviewed-by: Konrad Rzeszutek Wilk <[email protected]>
Tested-by: Boris Ostrovsky <[email protected]>

Author: Christoph Hellwig

kernel/dma/swiotlb.c

@@ -369,6 +369,9 @@ void __init swiotlb_exit(void)
 	unsigned long tbl_vaddr;
 	size_t tbl_size, slots_size;
 
+	if (swiotlb_force == SWIOTLB_FORCE)
+		return;
+
 	if (!mem->nslabs)
 		return;