linux-kernel - Re: [PATCH v2 1/2] block: make __register

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Date:   Tue, 28 Sep 2021 10:57:18 +1000 (AEST)
From:   Finn Thain <fthain@...ux-m68k.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
cc:     axboe@...nel.dk, hch@....de, efremov@...ux.com, song@...nel.org,
        jejb@...ux.ibm.com, martin.petersen@...cle.com,
        viro@...iv.linux.org.uk, hare@...e.de, jack@...e.cz,
        ming.lei@...hat.com, tj@...nel.org, linux-raid@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Subject: Re: [PATCH v2 1/2] block: make __register_blkdev() return an error

On Mon, 27 Sep 2021, Luis Chamberlain wrote:

> diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
> index 5dc9b3d32415..be0627345b21 100644
> --- a/drivers/block/ataflop.c
> +++ b/drivers/block/ataflop.c
> @@ -1989,24 +1989,34 @@ static int ataflop_alloc_disk(unsigned int drive, unsigned int type)
>  
>  static DEFINE_MUTEX(ataflop_probe_lock);
>  
> -static void ataflop_probe(dev_t dev)
> +static int ataflop_probe(dev_t dev)
>  {
>  	int drive = MINOR(dev) & 3;
>  	int type  = MINOR(dev) >> 2;
> +	int err = 0;
>  
>  	if (type)
>  		type--;
>  
> -	if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS)
> -		return;
> +	if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS) {
> +		err = -EINVAL;
> +		goto out;
> +	}
> +
>  	mutex_lock(&ataflop_probe_lock);
>  	if (!unit[drive].disk[type]) {
> -		if (ataflop_alloc_disk(drive, type) == 0) {
> -			add_disk(unit[drive].disk[type]);
> +		err = ataflop_alloc_disk(drive, type);
> +		if (err == 0) {
> +			err = add_disk(unit[drive].disk[type]);
> +			if (err)
> +				blk_cleanup_disk(unit[drive].disk[type]);
>  			unit[drive].registered[type] = true;
>  		}
>  	}
>  	mutex_unlock(&ataflop_probe_lock);
> +
> +out:
> +	return err;
>  }
>  
>  static void atari_cleanup_floppy_disk(struct atari_floppy_struct *fs)

I think the change to ataflop_probe() would be more clear without adding 
an 'out' label, like your change to floppy.c:

> diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
> index 0434f28742e7..95a1c8ef62f7 100644
> --- a/drivers/block/floppy.c
> +++ b/drivers/block/floppy.c
> @@ -4517,21 +4517,27 @@ static int floppy_alloc_disk(unsigned int drive, unsigned int type)
>  
>  static DEFINE_MUTEX(floppy_probe_lock);
>  
> -static void floppy_probe(dev_t dev)
> +static int floppy_probe(dev_t dev)
>  {
>  	unsigned int drive = (MINOR(dev) & 3) | ((MINOR(dev) & 0x80) >> 5);
>  	unsigned int type = (MINOR(dev) >> 2) & 0x1f;
> +	int err = 0;
>  
>  	if (drive >= N_DRIVE || !floppy_available(drive) ||
>  	    type >= ARRAY_SIZE(floppy_type))
> -		return;
> +		return -EINVAL;
>  
>  	mutex_lock(&floppy_probe_lock);
>  	if (!disks[drive][type]) {
> -		if (floppy_alloc_disk(drive, type) == 0)
> -			add_disk(disks[drive][type]);
> +		if (floppy_alloc_disk(drive, type) == 0) {
> +			err = add_disk(disks[drive][type]);
> +			if (err)
> +				blk_cleanup_disk(disks[drive][type]);
> +		}
>  	}
>  	mutex_unlock(&floppy_probe_lock);
> +
> +	return err;
>  }
>  
>  static int __init do_floppy_init(void)

In floppy_probe(), I think you should return the potential error result 
from floppy_alloc_disk(), like you did in ataflop.c.