linux-kernel - Re: [PATCH 3/4] Simplify zram disk resizing interface

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Message-ID: <4E5CB734.2000103@redhat.com>
Date:	Tue, 30 Aug 2011 12:11:00 +0200
From:	Jerome Marchand <jmarchan@...hat.com>
To:	Nitin Gupta <ngupta@...are.org>
CC:	Greg KH <greg@...ah.com>, Pekka Enberg <penberg@...helsinki.fi>,
	Robert Jennings <rcj@...ux.vnet.ibm.com>,
	Linux Driver Project <devel@...uxdriverproject.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] Simplify zram disk resizing interface

On 08/24/2011 03:34 AM, Nitin Gupta wrote:
> Also remove unnecessary messages.
> 
> Signed-off-by: Nitin Gupta <ngupta@...are.org>
> ---
>  drivers/staging/zram/zram_drv.c |   42 +++++++++++---------------------------
>  drivers/staging/zram/zram_drv.h |    2 +-
>  2 files changed, 13 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
> index 81d6c43..d7fb207 100644
> --- a/drivers/staging/zram/zram_drv.c
> +++ b/drivers/staging/zram/zram_drv.c
> @@ -104,33 +104,16 @@ static int page_zero_filled(void *ptr)
>  	return 1;
>  }
>  
> -static void zram_set_disksize(struct zram *zram, size_t totalram_bytes)
> +static u64 zram_default_disksize_bytes(void)
>  {
> -	if (!zram->disksize) {
> -		pr_info(
> -		"disk size not provided. You can use disksize_kb module "
> -		"param to specify size.\nUsing default: (%u%% of RAM).\n",
> -		default_disksize_perc_ram
> -		);
> -		zram->disksize = default_disksize_perc_ram *
> -					(totalram_bytes / 100);
> -	}
> -
> -	if (zram->disksize > 2 * (totalram_bytes)) {
> -		pr_info(
> -		"There is little point creating a zram of greater than "
> -		"twice the size of memory since we expect a 2:1 compression "
> -		"ratio. Note that zram uses about 0.1%% of the size of "
> -		"the disk when not in use so a huge zram is "
> -		"wasteful.\n"
> -		"\tMemory Size: %zu kB\n"
> -		"\tSize you selected: %llu kB\n"
> -		"Continuing anyway ...\n",
> -		totalram_bytes >> 10, zram->disksize
> -		);
> -	}
> -
> -	zram->disksize &= PAGE_MASK;
> +	return ((totalram_pages << PAGE_SHIFT) *
> +		default_disksize_perc_ram / 100) & PAGE_MASK;
> +}
> +
> +static void zram_set_disksize(struct zram *zram, u64 size_bytes)
> +{
> +	zram->disksize = size_bytes;
> +	set_capacity(zram->disk, size_bytes >> SECTOR_SHIFT);
>  }
>  
>  static void zram_free_page(struct zram *zram, size_t index)
> @@ -632,7 +615,8 @@ int zram_init_device(struct zram *zram)
>  		return 0;
>  	}
>  
> -	zram_set_disksize(zram, totalram_pages << PAGE_SHIFT);
> +	if (!zram->disksize)
> +		zram_set_disksize(zram, zram_default_disksize_bytes());

With your next patch, this will not happen anymore, unless someone explicitly sets
the disk size to zero. If zero means default, it should be documented. It looks weird
anyway: if something like that should be done, it probably should be done in
disksize_store() for clarity.
Otherwise, your next patch should remove this chunk of code.

Jerome

>  
>  	zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
>  	if (!zram->compress_workmem) {
> @@ -658,8 +642,6 @@ int zram_init_device(struct zram *zram)
>  		goto fail;
>  	}
>  
> -	set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
> -
>  	/* zram devices sort of resembles non-rotational disks */
>  	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
>  
> @@ -735,7 +717,7 @@ static int create_device(struct zram *zram, int device_id)
>  	snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
>  
>  	/* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
> -	set_capacity(zram->disk, 0);
> +	zram_set_disksize(zram, 0);
>  
>  	/*
>  	 * To ensure that we always get PAGE_SIZE aligned
> diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h
> index 59b01d6..83e774c 100644
> --- a/drivers/staging/zram/zram_drv.h
> +++ b/drivers/staging/zram/zram_drv.h
> @@ -47,7 +47,7 @@ static const unsigned default_disksize_perc_ram = 25;
>   * Pages that compress to size greater than this are stored
>   * uncompressed in memory.
>   */
> -static const unsigned max_zpage_size = PAGE_SIZE / 4 * 3;
> +static const u64 max_zpage_size = PAGE_SIZE / 4 * 3;
>  
>  /*
>   * NOTE: max_zpage_size must be less than or equal to:

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