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 X-Spam-Level: X-Spam-Status: No, score=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C5373C4338F for ; Mon, 16 Aug 2021 21:39:40 +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 6C35A60EE4 for ; Mon, 16 Aug 2021 21:39:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 6C35A60EE4 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]:46696 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mFkKZ-00053b-Iu for qemu-devel@archiver.kernel.org; Mon, 16 Aug 2021 17:39:39 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52742) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mFkJT-00039P-Bt for qemu-devel@nongnu.org; Mon, 16 Aug 2021 17:38:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:36100) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mFkJR-0001R4-Oz for qemu-devel@nongnu.org; Mon, 16 Aug 2021 17:38:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629149909; 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=9cxh/WffuFalqtXOiJMJC7N+Y7qq0H+HLJqr3xK8fAM=; b=Hb44Lsl9TovJ7DmEu5owUuR4yvDsfo+M+k8lNZ8c1gVwL0HYgJl/s/9IFYUhVBWyKPQj5S MWXxgrUMvBidWZm8kG02dDKmA8syPUbGAMM+4XAqJRZ8uT7gzcgHWLF16Lb2eK1tJBY6v2 XQlDRf+MksLHFvWHX6E/3DDuFgLUYW0= 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-402-72bXWEZPOeWB3dEH-B4ZIw-1; Mon, 16 Aug 2021 17:38:26 -0400 X-MC-Unique: 72bXWEZPOeWB3dEH-B4ZIw-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 8EDA687122E; Mon, 16 Aug 2021 21:38:25 +0000 (UTC) Received: from redhat.com (ovpn-113-125.phx2.redhat.com [10.3.113.125]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E42283A47; Mon, 16 Aug 2021 21:38:24 +0000 (UTC) Date: Mon, 16 Aug 2021 16:38:23 -0500 From: Eric Blake To: Hanna Reitz Subject: Re: [PATCH v3 2/6] block: block-status cache for data regions Message-ID: <20210816213823.uocknsk4zgulrk3v@redhat.com> References: <20210812084148.14458-1-hreitz@redhat.com> <20210812084148.14458-3-hreitz@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210812084148.14458-3-hreitz@redhat.com> User-Agent: NeoMutt/20210205-719-68949a 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: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.698, 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: Kevin Wolf , Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Aug 12, 2021 at 10:41:44AM +0200, Hanna Reitz wrote: > As we have attempted before > (https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg06451.html, > "file-posix: Cache lseek result for data regions"; > https://lists.nongnu.org/archive/html/qemu-block/2021-02/msg00934.html, > "file-posix: Cache next hole"), this patch seeks to reduce the number of > SEEK_DATA/HOLE operations the file-posix driver has to perform. The > main difference is that this time it is implemented as part of the > general block layer code. > > We only use the cache for nodes without children (i.e. protocol nodes), > because that is where the problem is: Drivers that rely on block-status > implementations outside of qemu (e.g. SEEK_DATA/HOLE). > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/307 > Signed-off-by: Hanna Reitz > --- > +++ b/block.c > +/** > + * Check whether [offset, offset + bytes) overlaps with the cached > + * block-status data region. > + * > + * If so, and @pnum is not NULL, set *pnum to `bsc.data_end - offset`, > + * which is what bdrv_bsc_is_data()'s interface needs. > + * Otherwise, *pnum is not touched. Why duplicate this comment,... > + */ > +static bool bdrv_bsc_range_overlaps_locked(BlockDriverState *bs, > + int64_t offset, int64_t bytes, > + int64_t *pnum) > +{ > + BdrvBlockStatusCache *bsc = qatomic_rcu_read(&bs->block_status_cache); > + bool overlaps; > + > + overlaps = > + qatomic_read(&bsc->valid) && > + ranges_overlap(offset, bytes, bsc->data_start, > + bsc->data_end - bsc->data_start); > + > + if (overlaps && pnum) { > + *pnum = bsc->data_end - offset; > + } > + > + return overlaps; > +} > + > +/** > + * See block_int.h for this function's documentation. > + */ > +bool bdrv_bsc_is_data(BlockDriverState *bs, int64_t offset, int64_t *pnum) > +{ > + RCU_READ_LOCK_GUARD(); > + > + return bdrv_bsc_range_overlaps_locked(bs, offset, 1, pnum); > +} > + > +/** > + * See block_int.h for this function's documentation. ...but not these? But that's minor. Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org