linux-kernel - Re: [PATCH] zram: move comp allocation out of init

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Date:	Thu, 6 Mar 2014 14:31:44 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [PATCH] zram: move comp allocation out of init_lock

Hello Minchan,

On (03/06/14 17:26), Minchan Kim wrote:
> Hello Sergey,
> 
> On Tue, Mar 04, 2014 at 01:10:56PM +0300, Sergey Senozhatsky wrote:
> > While fixing lockdep spew of ->init_lock reported by Sasha Levin [1], Minchan
> > Kim noted [2] that it's better to move compression backend allocation (using
> > GPF_KERNEL) out of the ->init_lock lock, same way as with zram_meta_alloc(),
> > in order to prevent the same lockdep spew.
> > 
> > [1] https://lkml.org/lkml/2014/2/27/337
> > [2] https://lkml.org/lkml/2014/3/3/32
> > 
> > Cc: Sasha Levin <sasha.levin@...cle.com>
> > Reported-by: Minchan Kim <minchan@...nel.org>
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> 
> Thanks for looking.
> 
thanks for noting.

> > ---
> >  drivers/block/zram/zram_drv.c | 27 +++++++++++++++------------
> >  1 file changed, 15 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index 15d46f2..e4d536b 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -580,9 +580,10 @@ static ssize_t disksize_store(struct device *dev,
> >  		struct device_attribute *attr, const char *buf, size_t len)
> >  {
> >  	u64 disksize;
> > +	struct zcomp *comp;
> >  	struct zram_meta *meta;
> >  	struct zram *zram = dev_to_zram(dev);
> > -	int err;
> > +	int err = -EINVAL;
> >  
> >  	disksize = memparse(buf, NULL);
> >  	if (!disksize)
> > @@ -593,30 +594,32 @@ static ssize_t disksize_store(struct device *dev,
> >  	if (!meta)
> >  		return -ENOMEM;
> >  
> > +	comp = zcomp_create(zram->compressor, zram->max_comp_streams);
> > +	if (!comp) {
> > +		pr_info("Cannot initialise %s compressing backend\n",
> > +				zram->compressor);
> 
> -ENOMEM?
> 

yes. patch 'zram: return error-valued pointer from zcomp_create()'
changed zcomp_create() and it returns ERR_PTR() (-ENOMEM or -EINVAL)
now.

	-ss

> Otherwise,
> Acked-by: Minchan Kim <minchan@...nel.org>
> 
> 
> > +		goto out_cleanup;
> > +	}
> > +
> >  	down_write(&zram->init_lock);
> >  	if (init_done(zram)) {
> > +		up_write(&zram->init_lock);
> >  		pr_info("Cannot change disksize for initialized device\n");
> >  		err = -EBUSY;
> > -		goto out_free_meta;
> > -	}
> > -
> > -	zram->comp = zcomp_create(zram->compressor, zram->max_comp_streams);
> > -	if (!zram->comp) {
> > -		pr_info("Cannot initialise %s compressing backend\n",
> > -				zram->compressor);
> > -		err = -EINVAL;
> > -		goto out_free_meta;
> > +		goto out_cleanup;
> >  	}
> >  
> >  	zram->meta = meta;
> > +	zram->comp = comp;
> >  	zram->disksize = disksize;
> >  	set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
> >  	up_write(&zram->init_lock);
> >  
> >  	return len;
> >  
> > -out_free_meta:
> > -	up_write(&zram->init_lock);
> > +out_cleanup:
> > +	if (comp)
> > +		zcomp_destroy(comp);
> >  	zram_meta_free(meta);
> >  	return err;
> >  }
> > -- 
> > 1.9.0.382.g7f3562c
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> > Please read the FAQ at  http://www.tux.org/lkml/
> 
> -- 
> Kind regards,
> Minchan Kim
> 
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