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 3F60AE75459 for ; Tue, 3 Oct 2023 18:19:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231329AbjJCSTb (ORCPT ); Tue, 3 Oct 2023 14:19:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45110 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231158AbjJCSTb (ORCPT ); Tue, 3 Oct 2023 14:19:31 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9445A83 for ; Tue, 3 Oct 2023 11:18:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1696357121; 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: in-reply-to:in-reply-to:references:references; bh=Ujno44uN38TJ6v9sX5LBJoWOcWyxfyko7zJqPs45iPc=; b=Jup0AToDx8NG7DrnqayK9iC8UXNROpjOZkZ1OIUaYOSnMBIC0WoIDI/2sAr+bD7LBT+83E K97y5R3po2F+iFc4iNZRld06nek/0pQLCwj8RevmsnqC2lVIEGQCrMUECD0AWleRkSTE3N oJtrinEc71G3XbbRS7DCVTg//+6MCrs= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-646--Lvc-vhcOgegyk-uNRr0ww-1; Tue, 03 Oct 2023 14:18:38 -0400 X-MC-Unique: -Lvc-vhcOgegyk-uNRr0ww-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 11FD4101A550; Tue, 3 Oct 2023 18:18:38 +0000 (UTC) Received: from segfault.boston.devel.redhat.com (segfault.boston.devel.redhat.com [10.19.60.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id ED5F11006B70; Tue, 3 Oct 2023 18:18:37 +0000 (UTC) From: Jeff Moyer To: Jens Axboe Cc: io-uring Subject: Re: [PATCH] io_uring: don't allow IORING_SETUP_NO_MMAP rings on highmem pages References: <4c9eddf5-75d8-44cf-9365-a0dd3d0b4c05@kernel.dk> <08c0b5de-cf5e-432f-b8d6-a60204308d3a@kernel.dk> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Tue, 03 Oct 2023 14:24:22 -0400 In-Reply-To: <08c0b5de-cf5e-432f-b8d6-a60204308d3a@kernel.dk> (Jens Axboe's message of "Tue, 3 Oct 2023 10:27:29 -0600") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Jens Axboe writes: > On 10/3/23 10:30 AM, Jeff Moyer wrote: >> Hi, Jens, >> [snip] >> What do you think about throwing a printk_once in there that explains >> the problem? I'm worried that this will fail somewhat randomly, and it >> may not be apparent to the user why. We should also add documentation, >> of course, and encourage developers to add fallbacks for this case. > > For both cases posted, it's rather more advanced use cases. And 32-bit > isn't so prevalent anymore, thankfully. I was going to add to the man > pages explaining this failure case. Not sure it's worth adding a printk > for though. I try not to make decisions based on how prevalent I think a particular configuration is (mainly because I'm usually wrong). Anyway, it's not a big deal, I'm glad you gave it some thought. > FWIW, once I got an arm32 vm setup, it fails everytime for me. Not sure > how it'd do on 32-bit x86, similarly or more randomly. But yeah it's > definitely at the mercy of how things are mapped. ...and potentially the load on the system. Anyway, it's fine with me to keep it as is. We can always add a warning later if it ends up being a problem. Thanks! Jeff