From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752825AbdA3M2f (ORCPT <rfc822;w@1wt.eu>);
        Mon, 30 Jan 2017 07:28:35 -0500
Received: from verein.lst.de ([213.95.11.211]:49218 "EHLO newverein.lst.de"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751621AbdA3M20 (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 30 Jan 2017 07:28:26 -0500
Date: Mon, 30 Jan 2017 13:24:52 +0100
From: Christoph Hellwig <hch@lst.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: martin.petersen@oracle.com, Jens Axboe <axboe@kernel.dk>,
        linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        Bart Van Assche <bart.vanassche@sandisk.com>,
        Omar Sandoval <osandov@osandov.com>, Christoph Hellwig <hch@lst.de>
Subject: Re: [RFC PATCH] scsi, block: fix duplicate bdi name registration
        crashes
Message-ID: <20170130122452.GA9043@lst.de>
References: <148566590827.1627.3631056985359212959.stgit@dwillia2-desk3.amr.corp.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <148566590827.1627.3631056985359212959.stgit@dwillia2-desk3.amr.corp.intel.com>
User-Agent: Mutt/1.5.17 (2007-11-01)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi Dan,

this looks mostly fine to me.  A few code comments below, but except
for this there is another issue with it:  We still have drivers
that share a single request_queue for multiple gendisks, so I wonder

Also I think you probably want one patch for the block framework,
and one to switch SCSI over to it.

> +struct disk_devt {
> +	struct kref kref;
> +	void (*release)(struct kref *);
> +};
> +
> +static inline void put_disk_devt(struct disk_devt *disk_devt)
> +{
> +	if (disk_devt)
> +		kref_put(&disk_devt->kref, disk_devt->release);
> +}
> +
> +static inline void get_disk_devt(struct disk_devt *disk_devt)
> +{
> +	if (disk_devt)
> +		kref_get(&disk_devt->kref);
> +}

Given that we have a user-supplied release callack I'd much rather get
rid of the kref here, use a normal atomic_t and pass the disk_devt
structure to the release callback then a kref.