linux-kernel - Re: [PATCH 0/3] ramzswap: Eliminate stale data from compressed memory (v2)

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Message-ID: <4BE3C4CC.8050307@cs.helsinki.fi>
Date:	Fri, 07 May 2010 10:44:12 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Nitin Gupta <ngupta@...are.org>
CC:	Greg KH <greg@...ah.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	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 0/3] ramzswap: Eliminate stale data from compressed memory
 (v2)

Nitin Gupta kirjoitti:
> (tested on mainline but should apply to linux-next cleanly)
> 
>  * Changelog: v2 vs initial patches
>    - directly add swap free callback to block_device_operations
>      instead of using 'notifiers' for various swap events.
> 
> ramzswap driver creates RAM based block devices which can be
> used (only) as swap disks. Pages swapped to these disks are
> compressed and stored in memory itself.
> 
> However, these devices do not get any notification when a swap
> slot is freed (swap_map[i] reaches 0). So, we cannot free memory
> allocated corresponding to this swap slot. Such stale data can
> quickly accumulate in (compressed) memory defeating the whole
> purpose of such devices.
> 
> To overcome this problem, we now add a callback in struct
> block_device_operations which is called as soon as a swap
> slot is freed.
> 
> Nitin Gupta (3):
>   Add flag to identify block swap devices
>   Add swap slot free callback to block_device_operations
>   ramzswap: Handler for swap slot free callback
> 
>  drivers/staging/ramzswap/TODO           |    5 -----
>  drivers/staging/ramzswap/ramzswap_drv.c |   22 +++++++++++++---------
>  include/linux/blkdev.h                  |    2 ++
>  include/linux/swap.h                    |    1 +
>  mm/swapfile.c                           |    5 +++++
>  5 files changed, 21 insertions(+), 14 deletions(-)
>  delete mode 100644 drivers/staging/ramzswap/TODO

The series looks good to me:

Acked-by: Pekka Enberg <penberg@...helsinki.fi>
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