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Wed, 12 Nov 2025 18:20:21 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:2495:f9c3:243d:2a7e]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-bc36fa02c42sm462699a12.16.2025.11.12.18.20.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Nov 2025 18:20:20 -0800 (PST) Date: Thu, 13 Nov 2025 11:20:15 +0900 From: Sergey Senozhatsky To: Yuwen Chen Cc: axboe@kernel.dk, akpm@linux-foundation.org, bgeffon@google.com, licayy@outlook.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, liumartin@google.com, minchan@kernel.org, richardycc@google.com, senozhatsky@chromium.org Subject: Re: [PATCH v4] zram: Implement multi-page write-back Message-ID: References: <83d64478-d53c-441f-b5b4-55b5f1530a03@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 24DF34000A X-Stat-Signature: mgbtxrgx4y63inuj8j7h64qsu5bk1ibm X-Rspam-User: X-HE-Tag: 1763000421-296736 X-HE-Meta: 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 I5GIF/bV 9gcch+Jh5krkJ64b2xJ1TXL/CHbS3YrSR0kF4NBadCsylBqBuyU4P6lB+kR9EiH6aQYKx31l4YWi8nu0L1S58obalJeja07X2rRC9hNP2UGjpTZYSBOtF52rK+bY4nwPx36qoggFeXohfS+qmFSKEHqICgz9XH28a3MvhDqQsdIOWDaAtTBcb0P4drhmegCobet4Y/0xId1ruxxeattwDDJgq5ul9i61HmimW0Y5itL5krULHj7qW2ogrzQKZxbGR5UnB4VVqB4IpSxYEZezvY/NKCge6yJX8gpnULo90XZXRYwT5GYCCvLmzum81ZsSv7uyc+Mh8mTxjPQfK5mITolfgSFNWkWsSHBfpe9v1enhEPt0= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.