From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 31511CCFA1A for ; Tue, 11 Nov 2025 13:25:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=4i9gAbKSz3SyIVo03JvQ7d9thevi3d3A6g2Fu/hKrNA=; b=OKONkloPU7S9oBO+fbjr4MOezh 1VwKTiN1KFkVl1y+JwLcfmo64niX1WhDGLjNYDc5X5nqvmBdWwJIRKCVtCDZ6TcrmsCuuNfqSQuEj cdXIvnrAtG3+DTxX+BXXKBuTTVAvItHWArGouzoyN/AUtPgsQdFqPdUMfd12RfDn7X+xEDxrD4I3j K8TNlIuACEouJbjpNF/hFE2KZkWvIdUziOlVhh+rpdAR8lVR/GRoD8oqgNbx0ztAiN2nQFg49DlqK HBtjx+FvsqTiP4s/kw8gZBt5GB6zVkoftVMjtCHXmNX+nzPG5KZP2YqGszwxNJpH9XSHCodAjtY44 mZR3cYwg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vIoNV-00000007Eu4-0yl8; Tue, 11 Nov 2025 13:25:45 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vIoNT-00000007Etd-3B1X for linux-nvme@lists.infradead.org; Tue, 11 Nov 2025 13:25:44 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 85A5443C3E; Tue, 11 Nov 2025 13:25:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 932E9C19421; Tue, 11 Nov 2025 13:25:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762867541; bh=pCCfLAd+jgtFe99TpuN79KMHvJQ3KhJwNnbu3i0DEQo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XStIr7KEPP6lsJ/X20MeRdxMRZBEFVNwaZARKWvlQtCOPoPRKLcHrH6NLQAV2v07/ 4fIfceZuxnn9B2sL5dPnf9GWrmoIbf9rjVTjd+F3AVK0FQYrNDTx2ugHx8JHTSiY3+ fsBywk1tIHHffVtoK/ex4cnbbmPCIhBj9t4tMfbX/63moCK0nWyXRjFcf+yqJOLxXJ DGVcSrDdb0JR2GbynBsTPDpI6Ft9Hx7wl9njOZdkAj23oa3gmr6t+Y9+JS/kpjmz8w hyqygSpSxf0etucQWAouS/+hu7YqPAEj1unljxkuWEOGDf49pWiVUbGXQgyhMNLaPo 1z/ntfJjdDPeQ== Date: Tue, 11 Nov 2025 08:25:38 -0500 From: Keith Busch To: Yu Kuai Cc: Christoph Hellwig , Matthew Wilcox , Keith Busch , linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, axboe@kernel.dk Subject: Re: [PATCHv5 1/2] block: accumulate memory segment gaps per bio Message-ID: References: <20251014150456.2219261-1-kbusch@meta.com> <20251014150456.2219261-2-kbusch@meta.com> <20251111071439.GA4240@lst.de> <024631dc-3c65-49a8-a97a-f9110fd00e9a@fnnas.com> <20251111093903.GB14438@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251111_052543_817079_C0FAC92C X-CRM114-Status: GOOD ( 14.79 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Tue, Nov 11, 2025 at 06:14:24PM +0800, Yu Kuai wrote: > > > At least from blk_try_merge(), blk_discard_mergable() do return false, > however, following checking passed and we end up to the back merge patch. > > blk_try_merge > if (blk_discard_mergable()) > // false due to max_discard_segments is 1 > else if (...) > return ELEVATOR_BACK_MERGE > > Perhaps are you suggesting to change this to: > > enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) > { > - if (blk_discard_mergable(rq)) > - return ELEVATOR_DISCARD_MERGE; > - else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) > + if (req_op(rq) == REQ_OP_DISCARD) { > + if (blk_discard_mergable((rq))) > + return ELEVATOR_DISCARD_MERGE; > + return ELEVATOR_NO_MERGE; > + } > + > + if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) > return ELEVATOR_BACK_MERGE; > - else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) > + if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) > return ELEVATOR_FRONT_MERGE; > return ELEVATOR_NO_MERGE; > } > > And the same for other callers for blk_discard_mergable(). Ah, so we're merging a discard for a device that doesn't support vectored discard. I think we still want to be able to front/back merge such requests, though.