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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA1B1C636D4 for ; Wed, 15 Feb 2023 20:33:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229748AbjBOUdM (ORCPT ); Wed, 15 Feb 2023 15:33:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51418 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229584AbjBOUdM (ORCPT ); Wed, 15 Feb 2023 15:33:12 -0500 Received: from wout4-smtp.messagingengine.com (wout4-smtp.messagingengine.com [64.147.123.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 553E4367E5; Wed, 15 Feb 2023 12:33:11 -0800 (PST) Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailout.west.internal (Postfix) with ESMTP id 893453200900; Wed, 15 Feb 2023 15:33:10 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute1.internal (MEProxy); Wed, 15 Feb 2023 15:33:10 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= joshtriplett.org; h=cc:cc:content-transfer-encoding:content-type :date:date:from:from:in-reply-to:in-reply-to:message-id :mime-version:references:reply-to:sender:subject:subject:to:to; s=fm3; t=1676493190; x=1676579590; bh=BUDNZ68uRUNtVZa35o8Wuor6C LvW1YtTpOzM6OuHyl4=; b=Yd+xtUGf6EcrVy5GyRv988NQK2dNattCbY3Dp9mUl kkitD8Pw4/L5Q08c0PCtkV454bF16PkcV5XybKbOd1/xq8fZU31etMvj8FnlJBMn d1UXPmwBOkUXD/m58UYovDNk0KdjjR4T8HLVDWFCMAa9bqh7bfhf01v2CJZy+Qhx Qmkm/tkQMhZTyHfi7iAtqKeYNVQdi2tHRgRR9f8yj0HN6s3mHieHlpV2J8H5cf/2 i3cQ519Hz1eczH9/whol7V11AvAFkXLkxdMHXFfoQxHkUieJeczOXqKTNDxEYOTE HNresvFBU2swzRWz2mQmCs6g8IdAuur76tDP3CZvumAUg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:date:date:feedback-id:feedback-id:from:from :in-reply-to:in-reply-to:message-id:mime-version:references :reply-to:sender:subject:subject:to:to:x-me-proxy:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm1; t=1676493190; x= 1676579590; bh=BUDNZ68uRUNtVZa35o8Wuor6CLvW1YtTpOzM6OuHyl4=; b=M WHPKvAu2rXAyeSQ+biaijKHxHObyyQ4HK/6DwpA49wZsQhY+khj9vYbARIX+/hj8 5MT45xD4CCyqUanF5/OIQq3HQfD5mcBhs7pMLikcqjLupt0CwhjJOEhoM7FGw2g1 CRHp+Mm3ER1f11VzmAHbkrsBdR3FA94t+ziRaiSu3WOwCFzZ3CdRqMK4DFPvoRjF a1Mq7Bd9i820ArFNamvRHZhX9+IvmjI5g1raMp5yitxjUzpGoP1tRUMH4OcWXq1N 1EbC+PzLCWS89AuyPxSDAWCJW+F8sm+ijSFoOiRxsc5F4iaEICpIERcUcryA+8kY Qn7suqGkO8pO3IQ+Hk5HA== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvhedrudeihedgudefudcutefuodetggdotefrod ftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfgh necuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmd enucfjughrpeffhffvvefukfhfgggtugfgjgesthekredttddtjeenucfhrhhomheplfho shhhucfvrhhiphhlvghtthcuoehjohhshhesjhhoshhhthhrihhplhgvthhtrdhorhhgqe enucggtffrrghtthgvrhhnpeegiefhvedvkeelgffgjeejuefguddugefghfejheekgeeh ledtudejffejkeehfeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhgrih hlfhhrohhmpehjohhshhesjhhoshhhthhrihhplhgvthhtrdhorhhg X-ME-Proxy: Feedback-ID: i83e94755:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Wed, 15 Feb 2023 15:33:09 -0500 (EST) Date: Wed, 15 Feb 2023 12:33:08 -0800 From: Josh Triplett To: Jens Axboe Cc: Pavel Begunkov , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv2] io_uring: Support calling io_uring_register with a registered ring fd Message-ID: References: <03895f24-3540-dae9-1cdd-e3f6d901dec6@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <03895f24-3540-dae9-1cdd-e3f6d901dec6@kernel.dk> Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Wed, Feb 15, 2023 at 10:44:38AM -0700, Jens Axboe wrote: > On 2/14/23 5:42 PM, Josh Triplett wrote: > > Add a new flag IORING_REGISTER_USE_REGISTERED_RING (set via the high bit > > of the opcode) to treat the fd as a registered index rather than a file > > descriptor. > > > > This makes it possible for a library to open an io_uring, register the > > ring fd, close the ring fd, and subsequently use the ring entirely via > > registered index. > > This looks pretty straight forward to me, only real question I had > was whether using the top bit of the register opcode for this is the > best choice. But I can't think of better ways to do it, and the space > is definitely big enough to do that, so looks fine to me. It seemed like the cleanest way available given the ABI of io_uring_register, yeah. > One more comment below: > > > + if (use_registered_ring) { > > + /* > > + * Ring fd has been registered via IORING_REGISTER_RING_FDS, we > > + * need only dereference our task private array to find it. > > + */ > > + struct io_uring_task *tctx = current->io_uring; > > I need to double check if it's guaranteed we always have current->io_uring > assigned here. If the ring is registered we certainly will have it, but > what if someone calls io_uring_register(2) without having a ring setup > upfront? > > IOW, I think we need a NULL check here and failing the request at that > point. The next line is: + if (unlikely(!tctx || fd >= IO_RINGFD_REG_MAX)) The first part of that condition is the NULL check you're looking for, right? - Josh Triplett