From 8ba816b23abd2a9a05705f3d00b8653f8be73015 Mon Sep 17 00:00:00 2001 From: Yu Kuai Date: Tue, 26 Apr 2022 10:21:33 +0800 Subject: [PATCH] null-blk: save memory footprint for struct nullb_cmd Total 16 bytes can be saved in two ways: 1) The field 'bio' will only be used in bio based mode, and the field 'rq' will only be used in mq mode. Since they won't be used in the same time, declare a union for them. 2) The field 'bool fake_timeout' can be placed in the hole after the field 'error'. Signed-off-by: Yu Kuai Link: https://lore.kernel.org/r/20220426022133.3999006-1-yukuai3@huawei.com Signed-off-by: Jens Axboe --- drivers/block/null_blk/null_blk.h | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h index 78eb56b0ca55..4525a65e1b23 100644 --- a/drivers/block/null_blk/null_blk.h +++ b/drivers/block/null_blk/null_blk.h @@ -16,13 +16,15 @@ #include struct nullb_cmd { - struct request *rq; - struct bio *bio; + union { + struct request *rq; + struct bio *bio; + }; unsigned int tag; blk_status_t error; + bool fake_timeout; struct nullb_queue *nq; struct hrtimer timer; - bool fake_timeout; }; struct nullb_queue {