linux-kernel - Re: [PATCH v4 7/7] zram: writeback throttle

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Date:   Mon, 3 Dec 2018 14:50:26 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Joey Pabalinas <joeypabalinas@...il.com>
Subject: Re: [PATCH v4 7/7] zram: writeback throttle

On (12/03/18 11:40), Minchan Kim wrote:
[..]
> +	down_read(&zram->init_lock);
> +	atomic64_set(&zram->stats.bd_wb_limit, val);
> +	if (val == 0)
> +		zram->stop_writeback = false;
> +	up_read(&zram->init_lock);

[..]

> +		if (zram->stop_writeback) {
> +			ret = -EIO;
> +			break;
> +		}
> +
>  		if (!blk_idx) {
>  			blk_idx = alloc_block_bdev(zram);
>  			if (!blk_idx) {
> @@ -694,6 +732,11 @@ static ssize_t writeback_store(struct device *dev,
>  		zram_set_element(zram, index, blk_idx);
>  		blk_idx = 0;
>  		atomic64_inc(&zram->stats.pages_stored);
> +		if (atomic64_add_unless(&zram->stats.bd_wb_limit,
> +					-1 << (PAGE_SHIFT - 12), 0)) {
> +			if (atomic64_read(&zram->stats.bd_wb_limit) == 0)
> +				zram->stop_writeback = true;
> +		}

Do we need ->stop_writeback? It should be identical to

	atomic64_read(&zram->stats.bd_wb_limit) == 0


Otherwise, looks good!

	-ss