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Date: Sat, 26 Nov 2016 15:37:01 +0900
From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Takashi Iwai <tiwai@suse.de>,
        Hyeoncheol Lee <cheol.lee@lge.com>, yjay.kim@lge.com,
        Sangseok Lee <sangseok.lee@lge.com>,
        Hugh Dickins <hughd@google.com>, stable@vger.kernel.org
Subject: Re: [PATCH v3 3/3] zram: support BDI_CAP_STABLE_WRITES
Message-ID: <20161126063701.GA521@tigerII>
References: <1480062914-25556-1-git-send-email-minchan@kernel.org>
 <1480062914-25556-4-git-send-email-minchan@kernel.org>
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In-Reply-To: <1480062914-25556-4-git-send-email-minchan@kernel.org>
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Hello Minchan,

On (11/25/16 17:35), Minchan Kim wrote:
[..]
> +static void zram_revalidate_disk(struct zram *zram)
> +{
> +	revalidate_disk(zram->disk);
> +	zram->disk->queue->backing_dev_info.capabilities |=
> +		BDI_CAP_STABLE_WRITES;
> +}
> +
>  /*
>   * Check if request is within bounds and aligned on zram logical blocks.
>   */
> @@ -1094,7 +1102,7 @@ static ssize_t disksize_store(struct device *dev,
>  	zram->comp = comp;
>  	zram->disksize = disksize;
>  	set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
> -	revalidate_disk(zram->disk);
> +	zram_revalidate_disk(zram);
>  	up_write(&zram->init_lock);
>  
>  	return len;
> @@ -1142,7 +1150,7 @@ static ssize_t reset_store(struct device *dev,
>  	/* Make sure all the pending I/O are finished */
>  	fsync_bdev(bdev);
>  	zram_reset_device(zram);
> -	revalidate_disk(zram->disk);
> +	zram_revalidate_disk(zram);
>  	bdput(bdev);
>  
>  	mutex_lock(&bdev->bd_mutex);

why not set it just once, when we allocate queue/disk and configure both
of them:  in zram_add()

	queue->backing_dev_info.capabilities |= BDI_CAP_CGROUP_WRITEBACK;

	-ss