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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 344D0C433EF for ; Wed, 6 Oct 2021 20:39:18 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 00D6561058 for ; Wed, 6 Oct 2021 20:39:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 00D6561058 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:51376 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mYDh7-00040a-7T for qemu-devel@archiver.kernel.org; Wed, 06 Oct 2021 16:39:17 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34106) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mYDft-0002Do-MP for qemu-devel@nongnu.org; Wed, 06 Oct 2021 16:38:01 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:30702) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mYDfr-0005UZ-0g for qemu-devel@nongnu.org; Wed, 06 Oct 2021 16:38:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1633552678; 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=5+CbZDGI+1hFQiTK7BxMhlNLlP2qW21uKqtxdh2ZyXg=; b=ak4PYwm5CWgFUmtIWCPMYu2BOIbYzNL4SxmhUXXUtl3QgN1RLk0EJlmXymPfcKBGWyl9pu UCplP2kUKCLijBrkMKooqrYMyatirrpSIHHl2EMLYHVeHHsPyaGlysbtSAADLHwZWkHMPD 1xG01oDO5DDNP9cZuyySHJYUTxm8F+w= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-428-byNJM8eFMHa3hVzIm2JQdw-1; Wed, 06 Oct 2021 16:37:56 -0400 X-MC-Unique: byNJM8eFMHa3hVzIm2JQdw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E907F362F8; Wed, 6 Oct 2021 20:37:55 +0000 (UTC) Received: from redhat.com (ovpn-113-79.phx2.redhat.com [10.3.113.79]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B73A25D6D5; Wed, 6 Oct 2021 20:37:52 +0000 (UTC) Date: Wed, 6 Oct 2021 15:37:51 -0500 From: Eric Blake To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH 12/12] block-backend: drop INT_MAX restriction from blk_check_byte_request() Message-ID: <20211006203751.jhsy424prywt27b3@redhat.com> References: <20211006131718.214235-1-vsementsov@virtuozzo.com> <20211006131718.214235-13-vsementsov@virtuozzo.com> MIME-Version: 1.0 In-Reply-To: <20211006131718.214235-13-vsementsov@virtuozzo.com> User-Agent: NeoMutt/20210205-815-1dd940 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.05, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, ehabkost@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, hreitz@redhat.com, stefanha@redhat.com, crosa@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Oct 06, 2021 at 03:17:18PM +0200, Vladimir Sementsov-Ogievskiy wrote: > blk_check_bytes_request is called from blk_co_do_preadv, > blk_co_do_pwritev_part, blk_co_do_pdiscard and blk_co_copy_range > before (maybe) calling throttle_group_co_io_limits_intercept() (which > has int64_t argument) and then calling corresponding bdrv_co_ function. > bdrv_co_ functions are OK with int64_t bytes as well. > > So dropping the check for INT_MAX we just get same restrictions as in > bdrv_ layer: discard and write-zeroes goes through > bdrv_check_qiov_request() and are allowed to be 64bit. Other requests > go through bdrv_check_request32() and still restricted by INT_MAX > boundary. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > block/block-backend.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Deceptively short, but this is the one where a mistake would hurt. Thankfully, I agree with your analysis that the call stack is still checking 32-bit limits on read/write, and that discard/zero requests can now go up to 63-bit sizing if everything else in the call stack is ready; plus the fact that we are careful both in our drivers to document actual limits (whether 32-bit or even smaller), and in the block code to honor those limits (breaking larger requests into chunks before reaching this far). Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org