[PATCH] zram: move comp allocation out of init_lock

[PATCH] zram: move comp allocation out of init_lock

[Sergey Senozhatsky]

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@oracle.com>
Reported-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 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);
+		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

Re: [PATCH] zram: move comp allocation out of init_lock

[Jerome Marchand]

On 03/04/2014 11:10 AM, 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@oracle.com>
> Reported-by: Minchan Kim <minchan@kernel.org>
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> ---
>  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);
> +		goto out_cleanup;
> +	}
> +

zcomp_create() could fail because of a failed allocation, in which case
ENOMEM would be more appropriate. I guess zcomp_create() should return
an errno in case of failure.
But that's an other problem than the one addressed in this patch:

Acked-by: Jerome Marchand <jmarchan@redhat.com>

>  	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;
>  }
> 

Re: [PATCH] zram: move comp allocation out of init_lock

[Sergey Senozhatsky]

On (03/05/14 15:57), Jerome Marchand wrote:
> On 03/04/2014 11:10 AM, 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@oracle.com>
> > Reported-by: Minchan Kim <minchan@kernel.org>
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> > ---
> >  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);
> > +		goto out_cleanup;
> > +	}
> > +
> 
> zcomp_create() could fail because of a failed allocation, in which case
> ENOMEM would be more appropriate. I guess zcomp_create() should return
> an errno in case of failure.
> But that's an other problem than the one addressed in this patch:
> 

There are two possible cases of failed zcomp_create(). One is,
you're right, -ENOMEM. The second one is request of unsupported
compression algorithm - -EINVAL. agree, it makes sense to return
ERR_PTR() from zcomp_create(): -EINVAL or -ENOMEM.

	-ss

> Acked-by: Jerome Marchand <jmarchan@redhat.com>
> 
> >  	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;
> >  }
> > 
> 

Re: [PATCH] zram: move comp allocation out of init_lock

[Minchan Kim]

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@oracle.com>
> Reported-by: Minchan Kim <minchan@kernel.org>
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

Thanks for looking.

> ---
>  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?

Otherwise,
Acked-by: Minchan Kim <minchan@kernel.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
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

-- 
Kind regards,
Minchan Kim

Re: [PATCH] zram: move comp allocation out of init_lock

[Sergey Senozhatsky]

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@oracle.com>
> > Reported-by: Minchan Kim <minchan@kernel.org>
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.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@kernel.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
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> 
> -- 
> Kind regards,
> Minchan Kim
>