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Date: Tue, 5 May 2020 14:44:23 +0200
From: Christoph Hellwig <hch@....de>
To: Stefan Haberland <sth@...ux.ibm.com>
Cc: Christoph Hellwig <hch@....de>, axboe@...nel.dk,
linux-block@...r.kernel.org, hoeppner@...ux.ibm.com,
linux-s390@...r.kernel.org, heiko.carstens@...ibm.com,
gor@...ux.ibm.com, borntraeger@...ibm.com,
linux-kernel@...r.kernel.org,
Peter Oberparleiter <oberpar@...ux.ibm.com>
Subject: Re: [PATCH 1/1] s390/dasd: remove ioctl_by_bdev from DASD driver
On Mon, May 04, 2020 at 10:45:33AM +0200, Stefan Haberland wrote:
> > findthe corresponding device for example. Not sure if this is that easy.
>
> I did some additional research on this.
> What I could imagine:
>
> The gendisk->private_data pointer currently contains a pointer to
> the dasd_devmap structure. This one is also reachable by iterating
> over an exported dasd_hashlist.
> So I could export the dasd_hashlist symbol, iterate over it and try
> to find the dasd_devmap pointer I have from the gendisk->private_data
> pointer.
> This would ensure that the gendisk belongs to the DASD driver and I
> could use the additional information that is somehow reachable through
> the gendisk->private_data pointer.
>
> But again, I am not sure if this additional code and effort is needed.
> From my point of view checking the gendisk->major for DASD_MAJOR is
> OK to ensure that the device belongs to the DASD driver.
With CONFIG_DEBUG_BLOCK_EXT_DEVT you can't rely on major numbers.
And compared to all the complications I think the biodasdinfo method
is the least of all those evils. Jens, any opinion?
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