linux-kernel - Re: [PATCH v3 3/4] block: add support for notifications

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Date: Wed, 26 Jun 2024 13:46:50 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Daniel Golle <daniel@...rotopia.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Ulf Hansson <ulf.hansson@...aro.org>,
 Hauke Mehrtens <hauke@...ke-m.de>, Felix Fietkau <nbd@....name>,
 Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
 Dave Chinner <dchinner@...hat.com>, Jan Kara <jack@...e.cz>,
 Christian Brauner <brauner@...nel.org>,
 Thomas Weißschuh <linux@...ssschuh.net>,
 Al Viro <viro@...iv.linux.org.uk>, Li Lingfeng <lilingfeng3@...wei.com>,
 Christian Heusel <christian@...sel.eu>, Min Li <min15.li@...sung.com>,
 Avri Altman <avri.altman@....com>, Adrian Hunter <adrian.hunter@...el.com>,
 Hannes Reinecke <hare@...e.de>, Mikko Rapeli <mikko.rapeli@...aro.org>,
 Yeqi Fu <asuk4.q@...il.com>, Victor Shih <victor.shih@...esyslogic.com.tw>,
 Christophe JAILLET <christophe.jaillet@...adoo.fr>,
 Li Zhijian <lizhijian@...itsu.com>,
 "Ricardo B. Marliere" <ricardo@...liere.net>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
 linux-block@...r.kernel.org
Subject: Re: [PATCH v3 3/4] block: add support for notifications

On 6/25/24 8:51 PM, Daniel Golle wrote:
> +static int blk_call_notifier_add(struct device *dev)
> +{
> +	struct blk_device_list *new_blkdev;
> +
> +	new_blkdev = kmalloc(sizeof(*new_blkdev), GFP_KERNEL);
> +	if (!new_blkdev)
> +		return -ENOMEM;
> +
> +	new_blkdev->dev = dev;
> +	mutex_lock(&blk_notifier_lock);
> +	list_add_tail(&new_blkdev->list, &blk_devices);
> +	raw_notifier_call_chain(&blk_notifier_list, BLK_DEVICE_ADD, dev);
> +	mutex_unlock(&blk_notifier_lock);
> +
> +	return 0;
> +}

Nit: redundant newline.

> +device_initcall(blk_notifications_init);
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index b2f1362c4681..8d22ba03e3e1 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1687,4 +1687,12 @@ static inline bool bdev_can_atomic_write(struct block_device *bdev)
>  
>  #define DEFINE_IO_COMP_BATCH(name)	struct io_comp_batch name = { }
>  
> +
> +#ifdef CONFIG_BLOCK_NOTIFIERS

#if defined(CONFIG_BLOCK_NOTIFIERS)

> +#define BLK_DEVICE_ADD		1
> +#define BLK_DEVICE_REMOVE	2
> +void blk_register_notify(struct notifier_block *nb);
> +void blk_unregister_notify(struct notifier_block *nb);
> +#endif

Surely these helpers should have a !CONFIG_BLOCK_NOTIFIERS failure case
definition? Either that, or dummies. As it stands, any caller would need
to check if it's enabled or not.

-- 
Jens Axboe