Re: [PATCH 3/8] zram: factor out device reset from reset_store()

[Minchan Kim <minchan@kernel.org>]

On Tue, Mar 03, 2015 at 09:49:45PM +0900, Sergey Senozhatsky wrote:
> Device reset currently consists of two steps:
> a) holding ->bd_mutex we ensure that there are no device users
> (bdev->bd_openers)
> 
> b) and internal part (executed under bdev->bd_mutex and partially
> under zram->init_lock) that resets the device - frees allocated
> memory and returns the device back to its initial (un-init) state.
> 
> Dynamic device removal requires the same amount of work and checks.
> We can reuse internal cleanup part (b) zram_reset_device(), but step (a)
> is done in sysfs ATTR reset_store() handler.
> 
> Rename step (b) from zram_reset_device() to zram_reset_device_internal()

Nitpick:
Usually, we have used double underbar for internal functions(ie, __zram_reset_device).


> and factor out step (a) to zram_reset_device(). Both reset_store() and
> dynamic device removal will use zram_reset_device().
> 
> For readability let's keep them separated.
> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> ---
>  drivers/block/zram/zram_drv.c | 135 +++++++++++++++++++++---------------------
>  1 file changed, 67 insertions(+), 68 deletions(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 6707b7b..59662dc 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -729,48 +729,6 @@ static void zram_bio_discard(struct zram *zram, u32 index,
>  	}
>  }
>  
> -static void zram_reset_device(struct zram *zram)
> -{
> -	struct zram_meta *meta;
> -	struct zcomp *comp;
> -	u64 disksize;
> -
> -	down_write(&zram->init_lock);
> -
> -	zram->limit_pages = 0;
> -
> -	if (!init_done(zram)) {
> -		up_write(&zram->init_lock);
> -		return;
> -	}
> -
> -	meta = zram->meta;
> -	comp = zram->comp;
> -	disksize = zram->disksize;
> -	/*
> -	 * Refcount will go down to 0 eventually and r/w handler
> -	 * cannot handle further I/O so it will bail out by
> -	 * check zram_meta_get.
> -	 */
> -	zram_meta_put(zram);
> -	/*
> -	 * We want to free zram_meta in process context to avoid
> -	 * deadlock between reclaim path and any other locks.
> -	 */
> -	wait_event(zram->io_done, atomic_read(&zram->refcount) == 0);
> -
> -	/* Reset stats */
> -	memset(&zram->stats, 0, sizeof(zram->stats));
> -	zram->disksize = 0;
> -	zram->max_comp_streams = 1;
> -	set_capacity(zram->disk, 0);
> -
> -	up_write(&zram->init_lock);
> -	/* I/O operation under all of CPU are done so let's free */
> -	zram_meta_free(meta, disksize);
> -	zcomp_destroy(comp);
> -}
> -
>  static ssize_t disksize_store(struct device *dev,
>  		struct device_attribute *attr, const char *buf, size_t len)
>  {
> @@ -829,16 +787,54 @@ out_free_meta:
>  	return err;
>  }
>  
> -static ssize_t reset_store(struct device *dev,
> -		struct device_attribute *attr, const char *buf, size_t len)
> +/* internal device reset part -- cleanup allocated memory and
> + * return back to initial state */
> +static void zram_reset_device_internal(struct zram *zram)
>  {
> -	int ret;
> -	unsigned short do_reset;
> -	struct zram *zram;
> -	struct block_device *bdev;
> +	struct zram_meta *meta;
> +	struct zcomp *comp;
> +	u64 disksize;
>  
> -	zram = dev_to_zram(dev);
> -	bdev = bdget_disk(zram->disk, 0);
> +	down_write(&zram->init_lock);
> +
> +	zram->limit_pages = 0;
> +
> +	if (!init_done(zram)) {
> +		up_write(&zram->init_lock);
> +		return;
> +	}
> +
> +	meta = zram->meta;
> +	comp = zram->comp;
> +	disksize = zram->disksize;
> +	/*
> +	 * Refcount will go down to 0 eventually and r/w handler
> +	 * cannot handle further I/O so it will bail out by
> +	 * check zram_meta_get.
> +	 */
> +	zram_meta_put(zram);
> +	/*
> +	 * We want to free zram_meta in process context to avoid
> +	 * deadlock between reclaim path and any other locks.
> +	 */
> +	wait_event(zram->io_done, atomic_read(&zram->refcount) == 0);
> +
> +	/* Reset stats */
> +	memset(&zram->stats, 0, sizeof(zram->stats));
> +	zram->disksize = 0;
> +	zram->max_comp_streams = 1;
> +	set_capacity(zram->disk, 0);
> +
> +	up_write(&zram->init_lock);
> +	/* I/O operation under all of CPU are done so let's free */
> +	zram_meta_free(meta, disksize);
> +	zcomp_destroy(comp);
> +}
> +
> +static int zram_reset_device(struct zram *zram)
> +{
> +	int ret = 0;
> +	struct block_device *bdev = bdget_disk(zram->disk, 0);
>  
>  	if (!bdev)
>  		return -ENOMEM;
> @@ -850,31 +846,34 @@ static ssize_t reset_store(struct device *dev,
>  		goto out;
>  	}
>  
> -	ret = kstrtou16(buf, 10, &do_reset);
> -	if (ret)
> -		goto out;
> -
> -	if (!do_reset) {
> -		ret = -EINVAL;
> -		goto out;
> -	}
> -
>  	/* Make sure all pending I/O is finished */
>  	fsync_bdev(bdev);
> -	zram_reset_device(zram);
> -
> -	mutex_unlock(&bdev->bd_mutex);
> -	revalidate_disk(zram->disk);
> -	bdput(bdev);
> -
> -	return len;
> -
> +	zram_reset_device_internal(zram);
>  out:
>  	mutex_unlock(&bdev->bd_mutex);
>  	bdput(bdev);
>  	return ret;
>  }
>  
> +static ssize_t reset_store(struct device *dev,
> +		struct device_attribute *attr, const char *buf, size_t len)
> +{
> +	int ret;
> +	unsigned short do_reset;
> +	struct zram *zram;
> +
> +	zram = dev_to_zram(dev);
> +	ret = kstrtou16(buf, 10, &do_reset);
> +	if (ret)
> +		return ret;
> +
> +	if (!do_reset)
> +		return -EINVAL;
> +
> +	ret = zram_reset_device(zram);
> +	return ret ? ret : len;
> +}
> +
>  static void __zram_make_request(struct zram *zram, struct bio *bio)
>  {
>  	int offset, rw;
> @@ -1167,7 +1166,7 @@ static void zram_remove(struct zram *zram)
>  	sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
>  			&zram_disk_attr_group);
>  
> -	zram_reset_device(zram);
> +	zram_reset_device_internal(zram);
>  	idr_remove(&zram_index_idr, zram->disk->first_minor);
>  	blk_cleanup_queue(zram->disk->queue);
>  	del_gendisk(zram->disk);
> -- 
> 2.3.1.167.g7f4ba4b
> 

-- 
Kind regards,
Minchan Kim