linux-kernel - Re: [PATCH] block: switch to pr_warn() in __device_add

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Date:   Sun, 11 Oct 2020 16:53:22 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     Rustam Kovhaev <rkovhaev@...il.com>, axboe@...nel.dk,
        linux-block@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: switch to pr_warn() in __device_add_disk()

On 10/11/20 3:03 PM, Rustam Kovhaev wrote:
> syzbot triggered a warning while fuzzing with failslab fault injection
> enabled
> let's convert WARN_ON() to pr_warn()
> 
> Reported-and-tested-by: syzbot+f41893bb8c45cd18cf08@...kaller.appspotmail.com
> Link: https://syzkaller.appspot.com/bug?extid=f41893bb8c45cd18cf08
> Signed-off-by: Rustam Kovhaev <rkovhaev@...il.com>
> ---
>   block/genhd.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index 99c64641c314..be9ce35cf0fe 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -822,7 +822,8 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk,
>   		/* Register BDI before referencing it from bdev */
>   		dev->devt = devt;
>   		ret = bdi_register(bdi, "%u:%u", MAJOR(devt), MINOR(devt));
> -		WARN_ON(ret);
> +		if (ret)
> +			pr_warn("%s: failed to register backing dev info\n", disk->disk_name);
>   		bdi_set_owner(bdi, dev);
>   		blk_register_region(disk_devt(disk), disk->minors, NULL,
>   				    exact_match, exact_lock, disk);
> 
Please, don't. Where is the point in continuing here?
I'd rather have it fixed up properly, either by having a return value to 
__device_add_disk() or by allowing the caller to check (eg by checking 
GENHD_FL_UP) if the call succeeded.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@...e.de                              +49 911 74053 688
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