Re: [PATCH] nbd driver for 2.5+: enhanced diagnostics support

[viro@parcelfarce.linux.theplanet.co.uk]

On Mon, Jun 23, 2003 at 08:04:49PM -0600, Lou Langholtz wrote:
> This third patch (for enhancing diagnostics support) applies 
> incrementally after my last LKML'd patch (for cosmetic changes). These 
> changes introduce configurable KERN_DEBUG level printk output for a 
> variety of different things that the driver does and provides the 
> framework for enhanced future debugging support as well.
> 
> As always, comments welcome!

> +	case BLKROSET: return "set-read-only";
> +	case BLKROGET: return "get-read-only";
> +	case BLKGETSIZE: return "block-get-size";
> +	case BLKFLSBUF: return "flush-buffer-cache";

The last 4 never make it to the driver (nor should they, being generic
ioctls).

> +	reply.magic = ntohl(reply.magic);
> +	if (reply.magic != NBD_REPLY_MAGIC) {
> +		printk(KERN_ERR "%s: Wrong magic (0x%lx)\n",
> +				lo->disk->disk_name,
> +				(unsigned long)reply.magic);

> +	reply.error = ntohl(reply.error);
> +	if (reply.error) {
> +		printk(KERN_ERR "%s: Other side returned error (%d)\n",
> +				lo->disk->disk_name, reply.error);

Generally a bad taste - it's harmless in this case, but such endianness
conversions in place are asking for trouble.

>  	lo->refcnt--;
> +	dprintk(DBG_RELEASE, "%s: %s refcnt=%d\n", lo->disk->disk_name,
> +			__FUNCTION__, lo->refcnt);
>  	/* N.B. Doesn't lo->file need an fput?? */
>  	return 0;

a) please, lose __FUNCTION__ - using it in macros is one thing, but
directly in a function that got a name shorter than `__FUNCTION__'?

b) no, it doesn't.

c) ->refcnt is never used.  How about losing it completely?  Along with
->open() and ->release()...

>  		sreq.flags = REQ_SPECIAL;
>  		nbd_cmd(&sreq) = NBD_CMD_DISC;

;-/

> +		sreq.sector = 0;
> +		sreq.nr_sectors = 0;

Umm... What for?

>  	if (sizeof(struct nbd_request) != 28) {
> -		printk(KERN_CRIT "Sizeof nbd_request needs to be 28 in order to work!\n" );
> +		printk(KERN_CRIT "nbd: Sizeof nbd_request needs to be 28 in order to work!\n" );
>  		return -EIO;
>  	}

FWIW, I'm less than sure that struct nbd_request is worth defining.
We use it in two places - the check above and nbd_send_req() where
it is filled and then its address is cast to char *.  It might be
better to use u32[7] directly and forget about all alignment issues.
Hell knows...  In this situation I would probably just define an
enum for offsets and be done with that.  Same goes for nbd_reply.