From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E70FA2D5957 for ; Sat, 21 Feb 2026 02:17:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771640272; cv=none; b=R6BLf9rG5DjvhzhDn8az9gzGm8hNST3PP9E/uLuEdSXAtDC+I4I4xFIUCxJ7noZB8G4IwS6BFNidtx4l8A2sZAT2sVV+zgY0zSG//gBNl0+aarfWzs+ReGawnWaq5Hn952kyxPq06kFAQPrYKXQZdHndEhpwrn0CPYWs7XhNMmI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771640272; c=relaxed/simple; bh=vK3Fkv92JKiQBiR+4ebF+Zo0ZjdiSrig6m5HRKXKHqA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=EL2tIWZs00A+qC5cu9on7GiqiNJ6JYoeSGwIA6zZleeX24GhEnJUAOldVZndzAQ+l6ztq3vNLbuVPHab7yLVGtnJgW5yWZGkLUClD3OI8fbquBB0cu8SKeucvOn2QmFAPvmQtq7fnpUJnzyQhaKx4s9L36kbWjzC36SxJw/s8Qc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=VBX2HDZT; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="VBX2HDZT" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1771640269; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=28qhnRDYbIMza8wCtEF45tLfB5UezN0tXVglAwww3+A=; b=VBX2HDZTQwEmRBZlO1AlzMmJMVhS4OgwcoOjQS7FgjBrvcaGxRXT0lssNG86tPzcsMleWv 6Kq09g4omTzWWV39zK3a1bZJY4l5f5YPxds0uTzuBFSDtj1t36nrINMO0TTisIxFRm4sUI 6N0Q2aLpF+VjJV8Osv94fXFw6hz+LKI= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-76-3w5VkhJyNSKzFIOPSprUfQ-1; Fri, 20 Feb 2026 21:17:44 -0500 X-MC-Unique: 3w5VkhJyNSKzFIOPSprUfQ-1 X-Mimecast-MFC-AGG-ID: 3w5VkhJyNSKzFIOPSprUfQ_1771640262 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 13965180049D; Sat, 21 Feb 2026 02:17:42 +0000 (UTC) Received: from fedora (unknown [10.72.116.24]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D676B19560A7; Sat, 21 Feb 2026 02:17:34 +0000 (UTC) Date: Sat, 21 Feb 2026 10:17:29 +0800 From: Ming Lei To: Caleb Sander Mateos Cc: Jens Axboe , Christoph Hellwig , Keith Busch , Sagi Grimberg , io-uring@vger.kernel.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, Anuj gupta , Kanchan Joshi Subject: Re: [PATCH v3 0/4] io_uring/uring_cmd: allow non-iopoll cmds with IORING_SETUP_IOPOLL Message-ID: References: <20260219172228.429479-1-csander@purestorage.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 On Fri, Feb 20, 2026 at 09:47:38AM -0800, Caleb Sander Mateos wrote: > On Fri, Feb 20, 2026 at 8:31 AM Ming Lei wrote: > > > > On Fri, Feb 20, 2026 at 08:22:29AM -0800, Caleb Sander Mateos wrote: > > > On Fri, Feb 20, 2026 at 8:11 AM Ming Lei wrote: > > > > > > > > On Fri, Feb 20, 2026 at 07:55:33AM -0800, Caleb Sander Mateos wrote: > > > > > On Fri, Feb 20, 2026 at 6:25 AM Ming Lei wrote: > > > > > > > > > > > > On Thu, Feb 19, 2026 at 10:22:23AM -0700, Caleb Sander Mateos wrote: > > > > > > > Currently, creating an io_uring with IORING_SETUP_IOPOLL requires all > > > > > > > requests issued to it to support iopoll. This prevents, for example, > > > > > > > using ublk zero-copy together with IORING_SETUP_IOPOLL, as ublk > > > > > > > zero-copy buffer registrations are performed using a uring_cmd. There's > > > > > > > no technical reason why these non-iopoll uring_cmds can't be supported. > > > > > > > They will either complete synchronously or via an external mechanism > > > > > > > that calls io_uring_cmd_done(), so they don't need to be polled. > > > > > > > > > > > > For sync uring command, it is fine to support for IOPOLL. > > > > > > > > > > > > However, there are async uring command, which may be completed in irq > > > > > > context, or in multishot way, at least the later isn't supported in > > > > > > io_do_iopoll() yet. > > > > > > > > > > Can you describe the issues you envision in more detail? > > > > > > > > Basically IOPOLL doesn't support multishot request yet. > > > > > > > > For example, when io_uring_mshot_cmd_post_cqe() is called and new cqe is > > > > queued, it can't be found from io_iopoll_check()<-io_uring_enter(IORING_ENTER_GETEVENTS). > > > > > > I don't think that's a new issue, though. You're right that > > > io_uring_mshot_cmd_post_cqe() assumes a non-REQ_F_IOPOLL request, so > > > it's up to the ->uring_cmd() implementation to ensure that (which ublk > > > already does). Since ublk's struct file_operations don't provide > > > ->uring_cmd_iopoll(), any ublk uring_cmds issued to an > > > IORING_SETUP_IOPOLL io_uring won't have REQ_F_IOPOLL set, so > > > io_uring_mshot_cmd_post_cqe() should work just fine. > > > > Please look in the following way: > > > > 1) without patch of `io_uring/uring_cmd: allow non-iopoll cmds with IORING_SETUP_IOPOLL`, > > multishot command submission can't succeed > > > > 2) with patch of "io_uring/uring_cmd: allow non-iopoll cmds with IORING_SETUP_IOPOLL", people > > may see hang forever in io_uring_enter() if multishot command is submitted > > in context IORING_SETUP_IOPOLL. > > Okay, I see what you mean. If ctx->iopoll_list is nonempty and a > non-REQ_F_IOPOLL request posts a completion without going through task > work, io_iopoll_check() won't check for CQEs already posted outside of > iopoll. I think it should be simple enough to check for CQEs > unconditionally in the io_iopoll_check() loop. Yeah, it shouldn't be hard to deal with. Thanks, Ming