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 4A07ACD4F3C for ; Mon, 18 May 2026 12:54:46 +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=rQgx3EHg/j1A6oSAAl3ca5ZUOXCGoWaoM7uAkfkD37A=; b=ccs6E+3PhbUsSqgnu0FSACpbLE SgGPnXTOkkdLfGVgUaeq2ORbY+CAm/IYHJR9RPLfAe5lujg9eQwa3LBl//jsPo/2uGRalz0NKQr/B j5y2OFyGJtj4KlXxOJbduJYd9HPY2FQkq1S/gcqIafwtaN9R19NrrkeNUgWcMzonTjdnNPkjvc/CF ISEt5SD31GxgMpKrzUYhiUVN6gcPhjUZ8WUKtcYt1RxmadDtc2Ggl9NdNPTLbhV/ZrMB9z5zX4dBV sKTh7+cYsklBTIYwSHwB+2Pp5XD31QhNEjsBLt2fHyoi77xRBQdzE1RjGKGut35p2GtczC1C3yuLo NRaRg0eQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wOxUa-0000000FiAM-3T9z; Mon, 18 May 2026 12:54:44 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wOxUY-0000000Fi9a-3rnD for linux-nvme@lists.infradead.org; Mon, 18 May 2026 12:54:44 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 003E768D09; Mon, 18 May 2026 14:54:39 +0200 (CEST) Date: Mon, 18 May 2026 14:54:39 +0200 From: Christoph Hellwig To: Pavel Begunkov Cc: Christoph Hellwig , Jens Axboe , Keith Busch , Sagi Grimberg , Alexander Viro , Christian Brauner , Andrew Morton , Sumit Semwal , Christian =?iso-8859-1?Q?K=F6nig?= , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, Nitesh Shetty , Kanchan Joshi , Anuj Gupta , Tushar Gohad , William Power , Phil Cayton , Jason Gunthorpe Subject: Re: [PATCH v3 04/10] block: introduce dma map backed bio type Message-ID: <20260518125439.GB5754@lst.de> References: <646ecd6fde8d9e146cb051efb514deb27ce3883e.1777475843.git.asml.silence@gmail.com> <20260513081929.GD5477@lst.de> <24833f76-2289-4859-86d1-9215b11a1258@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <24833f76-2289-4859-86d1-9215b11a1258@gmail.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260518_055443_102245_B17242F1 X-CRM114-Status: GOOD ( 13.92 ) 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 Mon, May 18, 2026 at 11:29:54AM +0100, Pavel Begunkov wrote: > On 5/13/26 09:19, Christoph Hellwig wrote: >>> + if (!bio_flagged(bio_src, BIO_DMABUF_MAP)) { >>> + bio->bi_io_vec = bio_src->bi_io_vec; >>> + } else { >>> + bio->dmabuf_map = bio_src->dmabuf_map; >>> + bio_set_flag(bio, BIO_DMABUF_MAP); >>> + } >> >> This is backwards, please avoid pointless negations: > > I can flip it, but compilers tend to prefer the true branch. E.g. this What kind of compiler optimization do you expect from code where both sides of the conditional assign different arms of the same union and just propagate the bit that was set?