linux-kernel - Re: [PATCH 14/19] floppy: use a separate gendisk for each media format

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Message-ID: <6a89e295-fd16-1930-c5a1-474c1ed47718@suse.de>
Date:   Fri, 4 Sep 2020 12:28:01 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Denis Efremov <efremov@...ux.com>,
        "David S. Miller" <davem@...emloft.net>,
        Song Liu <song@...nel.org>, Al Viro <viro@...iv.linux.org.uk>,
        Finn Thain <fthain@...egraphics.com.au>,
        Michael Schmitz <schmitzmic@...il.com>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-ide@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-m68k@...ts.linux-m68k.org
Subject: Re: [PATCH 14/19] floppy: use a separate gendisk for each media
 format

On 9/3/20 10:01 AM, Christoph Hellwig wrote:
> The floppy driver usually autodetects the media when used with the
> normal /dev/fd? devices, which also are the only nodes created by udev.
> But it also supports various aliases that force a given media format.
> That is currently supported using the blk_register_region framework
> which finds the floppy gendisk even for a 'mismatched' dev_t.  The
> problem with this (besides the code complexity) is that it creates
> multiple struct block_device instances for the whole device of a
> single gendisk, which can lead to interesting issues in code not
> aware of that fact.
> 
> To fix this just create a separate gendisk for each of the aliases
> if they are accessed.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>   drivers/block/floppy.c | 154 ++++++++++++++++++++++++++---------------
>   1 file changed, 97 insertions(+), 57 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@...e.de>

Cheers,

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