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Tue, 11 Nov 2025 21:18:06 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:2495:f9c3:243d:2a7e]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2984dbf550bsm15774345ad.33.2025.11.11.21.18.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Nov 2025 21:18:06 -0800 (PST) Date: Wed, 12 Nov 2025 14:18:01 +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: rspam04 X-Rspamd-Queue-Id: 3E3CE40007 X-Stat-Signature: 3pnynjpo1ktz43q4tsn9zbog4smzmiuq X-Rspam-User: X-HE-Tag: 1762924688-99490 X-HE-Meta: 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 nfk8nkGT 9zpNsCBPXsh63+0Vu+yII3iDxYLUpJZSqVJpLrPvJOm6qZXBl2PnoaGCv70C4BkPYJT0XDgtHg3O/8ME5amdo0EbwcDcpZ3GxVui6T+PJbgsiJPeXPS8KuosIVDpyH7DJQfSbc8c9LcS0sjh+yExqd6BGXtfESVKP1iQRy8ZYYPvMdozV40x+JTRzgwg1seXUNOgAvojghG8cZKUm8EwuBbhsCHznWNVouR8C6P96j/X+y2O3tQle3bI55w22wqUO1SPMfqtZ6cNtbDWPdjeMqzMRzslgn0TLndJuwocUeXugLNh3WlqWxc0myO4m4i44sDINWZGnBspuMqdKFlcw+MUTKdf9uxoKGfESuxIU61BPqZE= 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: [..] > + blk_start_plug(&plug); > + while ((req->pps = select_pp_slot(ctl))) { > spin_lock(&zram->wb_limit_lock); > if (zram->wb_limit_enable && !zram->bd_wb_limit) { > spin_unlock(&zram->wb_limit_lock); > @@ -774,15 +884,15 @@ static int zram_writeback_slots(struct zram *zram, struct zram_pp_ctl *ctl) > } > spin_unlock(&zram->wb_limit_lock); > > - if (!blk_idx) { > - blk_idx = alloc_block_bdev(zram); > - if (!blk_idx) { > + if (!req->blk_idx) { > + req->blk_idx = alloc_block_bdev(zram); > + if (!req->blk_idx) { > ret = -ENOSPC; > break; > } > } > > - index = pps->index; > + index = req->pps->index; > zram_slot_lock(zram, index); > /* > * scan_slots() sets ZRAM_PP_SLOT and relases slot lock, so > @@ -792,22 +902,32 @@ static int zram_writeback_slots(struct zram *zram, struct zram_pp_ctl *ctl) > */ > if (!zram_test_flag(zram, index, ZRAM_PP_SLOT)) > goto next; > - if (zram_read_from_zspool(zram, page, index)) > + if (zram_read_from_zspool(zram, req->page, index)) > goto next; > zram_slot_unlock(zram, index); > > - bio_init(&bio, zram->bdev, &bio_vec, 1, > + bio_init(&req->bio, zram->bdev, &req->bio_vec, 1, > REQ_OP_WRITE | REQ_SYNC); > - bio.bi_iter.bi_sector = blk_idx * (PAGE_SIZE >> 9); > - __bio_add_page(&bio, page, PAGE_SIZE, 0); > - > - /* > - * XXX: A single page IO would be inefficient for write > - * but it would be not bad as starter. > - */ > - err = submit_bio_wait(&bio); > + req->bio.bi_iter.bi_sector = req->blk_idx * (PAGE_SIZE >> 9); > + req->bio.bi_end_io = zram_writeback_endio; > + req->bio.bi_private = req; > + __bio_add_page(&req->bio, req->page, PAGE_SIZE, 0); > + > + list_del_init(&req->pps->entry); > + submit_bio(&req->bio); > + > + do { > + req = zram_writeback_next_request(req_pool, req_pool_cnt, &cnt_off); > + if (!req) { > + blk_finish_plug(&plug); > + wait_for_completion_io(&done); > + blk_start_plug(&plug); > + } > + } while (!req); Why do you do this do-while loop here?