linux-kernel - Re: [PATCH v4] zram: Implement multi-page write-back

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Message-ID: <x6ksirxv2xffhzpvdxmm5fa7r4b56mlh3kbhopljdsvwzg62wm@rrsslefk4rb4>
Date: Thu, 13 Nov 2025 11:20:15 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Yuwen Chen <ywen.chen@...mail.com>
Cc: axboe@...nel.dk, akpm@...ux-foundation.org, bgeffon@...gle.com, 
	licayy@...look.com, linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, liumartin@...gle.com, minchan@...nel.org, richardycc@...gle.com, 
	senozhatsky@...omium.org
Subject: Re: [PATCH v4] zram: Implement multi-page write-back

On (25/11/06 09:49), Yuwen Chen wrote:
> +static struct zram_wb_request *zram_writeback_next_request(struct zram_wb_request *pool,
> +	int pool_cnt, int *cnt_off)
> +{
> +	struct zram_wb_request *req = NULL;
> +	int i = 0;
> +
> +	for (i = *cnt_off; i < pool_cnt + *cnt_off; i++) {
> +		req = &pool[i % pool_cnt];
> +		if (!req->page) {
> +			/* This memory should be freed by the caller. */
> +			req->page = alloc_page(GFP_KERNEL);
> +			if (!req->page)
> +				continue;
> +		}
> +
> +		if (!test_and_set_bit(ZRAM_WB_REQUEST_ALLOCATED, &req->flags)) {
> +			*cnt_off = (i + 1) % pool_cnt;
> +			return req;
> +		}
> +	}
> +	return NULL;
> +}

So I wonder if things will look simpler (is this the word I'm looking
for?) if you just have two lists for requests: one list for completed/idle
requests and one list for in-flight requests (and you move requests
around accordingly).  Then you don't need to iterate the pool and check
flags, you just can check list_empty(&idle_requests) and take the first
(front) element.