linux-kernel - Re: [PATCHv4 2/6] zram: add writeback batch size device attr

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Message-Id: <20251120171738.84516c55e4aaeea0bf3b7725@linux-foundation.org>
Date: Thu, 20 Nov 2025 17:17:38 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Minchan Kim <minchan@...nel.org>, Yuwen Chen <ywen.chen@...mail.com>,
 Richard Chang <richardycc@...gle.com>, Brian Geffon <bgeffon@...gle.com>,
 Fengyu Lian <licayy@...look.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, linux-block@...r.kernel.org
Subject: Re: [PATCHv4 2/6] zram: add writeback batch size device attr

On Tue, 18 Nov 2025 16:29:56 +0900 Sergey Senozhatsky <senozhatsky@...omium.org> wrote:

> Introduce writeback_batch_size device attribute so that
> the maximum number of in-flight writeback bio requests
> can be configured at run-time per-device.  This essentially
> enables batched bio writeback.
> 
> ...
>
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -588,6 +588,42 @@ static ssize_t writeback_limit_show(struct device *dev,
>  	return sysfs_emit(buf, "%llu\n", val);
>  }
>  
> +static ssize_t writeback_batch_size_store(struct device *dev,
> +					  struct device_attribute *attr,
> +					  const char *buf, size_t len)
> +{
> +	struct zram *zram = dev_to_zram(dev);
> +	u32 val;
> +	ssize_t ret = -EINVAL;
> +
> +	if (kstrtouint(buf, 10, &val))
> +		return ret;
> +
> +	if (!val)
> +		val = 1;
> +
> +	down_read(&zram->init_lock);

down_write()?

> +	zram->wb_batch_size = val;
> +	up_read(&zram->init_lock);
> +	ret = len;
> +
> +	return ret;
> +}