linux-kernel - Re: [PATCH 2/3] Add swap slot free callback to block_device

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Date:	Fri, 07 May 2010 20:40:08 +1000
From:	Nigel Cunningham <nigel@...onice.net>
To:	ngupta@...are.org
CC:	Greg KH <greg@...ah.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Cyp <cyp561@...il.com>, Minchan Kim <minchan.kim@...il.com>,
	Al Viro <viro@...IV.linux.org.uk>,
	Christoph Hellwig <hch@...radead.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	driverdev <devel@...verdev.osuosl.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] Add swap slot free callback to block_device_operations

Hi.

On 07/05/10 19:48, Nitin Gupta wrote:
>>> +        if ((p->flags&   SWP_BLKDEV)&&
>>> +                disk->fops->swap_slot_free_notify)
>>> +            disk->fops->swap_slot_free_notify(p->bdev, offset);
>>
>> Is this p->flags&  SWP_BLKDEV logic reversed? (Don't you want the
>> notifier called for devices that aren't backed by a block device?)
>>
>
> No, the logic here is correct: ramzswap is a block device for which
> we want this callback. Though its a RAM backed, it is still a block
> device.
>
> (I hope it answers your question in the other mail also).

It does; thanks.

>> I also wonder whether leaving the p->flags&  SWP_BLKDEV part out might
>> be a good idea. Other potential notifier users?
>>
>
> For regular files, 'offset' used here makes little sense. For block devices,
> its simply offset in real device. Also, I doubt if *files* would ever
> like to have such a callback.

Okay.

Entire series Acked-by: Nigel Cunningham <nigel@...onice.net>

Thanks.

Nigel
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