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From: Minchan Kim <minchan@kernel.org>
Date: Sat, 26 Nov 2016 23:41:04 +0900
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, 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: <20161126144104.GA2189@blaptop>
References: <1480062914-25556-1-git-send-email-minchan@kernel.org>
 <1480062914-25556-4-git-send-email-minchan@kernel.org>
 <20161126063701.GA521@tigerII>
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In-Reply-To: <20161126063701.GA521@tigerII>
Sender: stable-owner@vger.kernel.org
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Hi Sergey,

On Sat, Nov 26, 2016 at 03:37:01PM +0900, Sergey Senozhatsky wrote:
> 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()

I should have mentioned the reason.
The revalidate_disk reset the BDI_CAP_STABLE_WRITES.

Thanks.