linux-kernel - Re: [PATCH 1/2] block: introduce new field flags in block

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Date:   Mon, 20 Nov 2023 11:45:14 +0100
From:   Hannes Reinecke <hare@...e.de>
To:     Yu Kuai <yukuai1@...weicloud.com>, axboe@...nel.dk
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH 1/2] block: introduce new field flags in block_device

On 11/20/23 10:38, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> There are multiple switches in struct block_device, use seperate bool
> fields for them is not gracefully. Add a new field flags and replace
> swithes to a bit, there are no functional changes, and preapre to add
> a new switch in the next patch.
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>   block/bdev.c              | 15 ++++++++-------
>   block/blk-core.c          |  7 ++++---
>   block/genhd.c             |  8 +++++---
>   block/ioctl.c             |  2 +-
>   include/linux/blk_types.h | 12 ++++++------
>   include/linux/blkdev.h    |  5 +++--
>   6 files changed, 27 insertions(+), 22 deletions(-)
> 
> diff --git a/block/bdev.c b/block/bdev.c
> index fc8d28d77495..cb849bcf61ae 100644
> --- a/block/bdev.c
> +++ b/block/bdev.c
> @@ -408,10 +408,10 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
>   	bdev->bd_partno = partno;
>   	bdev->bd_inode = inode;
>   	bdev->bd_queue = disk->queue;
> -	if (partno)
> -		bdev->bd_has_submit_bio = disk->part0->bd_has_submit_bio;
> +	if (partno && test_bit(BD_FLAG_HAS_SUBMIT_BIO, &disk->part0->flags))
> +		set_bit(BD_FLAG_HAS_SUBMIT_BIO, &bdev->flags);
>   	else
> -		bdev->bd_has_submit_bio = false;
> +		clear_bit(BD_FLAG_HAS_SUBMIT_BIO, &bdev->flags);
>   	bdev->bd_stats = alloc_percpu(struct disk_stats);
>   	if (!bdev->bd_stats) {
>   		iput(inode);

Couldn't you achieve the very same result by using 
'READ_ONCE()/WRITE_ONCE()' and keep the structure as-is?

Cheers,

Hannes--
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@...e.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Frankenstr. 146, 90461 Nürnberg
Managing Directors: I. Totev, A. McDonald, W. Knoblich
(HRB 36809, AG Nürnberg)