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

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Message-ID: <AANLkTinopOldGl3K648tnwmtMT3KhERIW8grokd45O3C@mail.gmail.com>
Date:	Mon, 17 May 2010 09:10:41 +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>,
	Nigel Cunningham <nigel@...onice.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Cyp <cyp561@...il.com>, driverdev <devel@...verdev.osuosl.org>,
	linux-kernel <linux-kernel@...r.kernel.org>, hughd@...gle.com
Subject: Re: [PATCH 0/3] ramzswap: Eliminate stale data from compressed memory 
	(v2 resend)

On Mon, May 17, 2010 at 8:32 AM, Nitin Gupta <ngupta@...are.org> wrote:
> Resending as Greg wanted.
>
> (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

Nitin, please retain ACKs when resending patches.

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

for the whole series.
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