wc_add_block     1529 drivers/md/dm-writecache.c 		BUG_ON(!wc_add_block(wb, e, GFP_NOIO));
wc_add_block     1539 drivers/md/dm-writecache.c 			if (!wc_add_block(wb, f, GFP_NOWAIT | __GFP_NOWARN))