From patchwork Wed Jun 23 15:01:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Max Reitz X-Patchwork-Id: 12340041 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=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 83A0AC4743C for ; Wed, 23 Jun 2021 15:03:41 +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 3836C6115A for ; Wed, 23 Jun 2021 15:03:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3836C6115A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58008 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lw4Pk-0007ue-7C for qemu-devel@archiver.kernel.org; Wed, 23 Jun 2021 11:03:40 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:56132) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lw4O9-0004pP-2e for qemu-devel@nongnu.org; Wed, 23 Jun 2021 11:02:02 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:25043) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lw4O3-0004kO-D9 for qemu-devel@nongnu.org; Wed, 23 Jun 2021 11:02:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624460514; 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; bh=cO8sxFgxu9zJtiMdUA+/zw6utx458UpzjvsfKCEphHY=; b=KXu26kwwVrEvSnftjOTURe7RpCyivQreArM0z4ZYAvYOo1fpkEmUM/OLO6FAoBr+99bR8M frCDtVzo+Y6nhVbv6wX/CC/TtYXUU0S5MWpR/287MgEi/FstqxVNSpihRcDi1FQQXRbLAy IearXO3CARl5rZ4AZSgUaRg26b/4gv0= 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-445-2HdPQkEPP62rgzxEPVrCvw-1; Wed, 23 Jun 2021 11:01:47 -0400 X-MC-Unique: 2HdPQkEPP62rgzxEPVrCvw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0623C1932481; Wed, 23 Jun 2021 15:01:46 +0000 (UTC) Received: from localhost (ovpn-113-73.ams2.redhat.com [10.36.113.73]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8899619D7C; Wed, 23 Jun 2021 15:01:45 +0000 (UTC) From: Max Reitz To: qemu-block@nongnu.org Subject: [PATCH v2 0/6] block: block-status cache for data regions Date: Wed, 23 Jun 2021 17:01:37 +0200 Message-Id: <20210623150143.188184-1-mreitz@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.373, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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 , Eric Blake , qemu-devel@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi, See the cover letter from v1 for the general idea: https://lists.nongnu.org/archive/html/qemu-block/2021-06/msg00843.html The biggest change here in v2 is that instead of having a common CoMutex protect the block-status cache, we’re using RCU now. So to read from the cache, or even to invalidate it, no lock is needed, only to update it with new data. Disclaimer: I have no experience with RCU in practice so far, neither in qemu nor anywhere else. So I hope I’ve used it correctly... Differences to v1 in detail: - Patch 2: - Moved BdrvBlockStatusCache.lock up to BDS, it is now the RCU writer lock - BDS.block_status_cache is now a pointer, so it can be replaced with RCU - Moved all cache access functionality into helper functions (bdrv_bsc_is_data(), bdrv_bsc_invalidate_range(), bdrv_bsc_fill()) in block.c - Guard BSC accesses with RCU (BSC.valid is to be accessed atomically, which allows resetting it without taking an RCU write lock) - Check QLIST_EMPTY(&bs->children) not just when reading from the cache, but when filling it, too (so we don’t need an RCU update when it won’t make sense) - Patch 3: Added - Dropped the block/nbd patch (because it would make NBD query a larger range; the patch’s intent was to get more information for free, which this would not be) git-backport-diff against v1: Key: [----] : patches are identical [####] : number of functional differences between upstream/downstream patch [down] : patch is downstream-only The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively 001/6:[----] [--] 'block: Drop BDS comment regarding bdrv_append()' 002/6:[0169] [FC] 'block: block-status cache for data regions' 003/6:[down] 'block: Clarify that @bytes is no limit on *pnum' 004/6:[----] [--] 'block/file-posix: Do not force-cap *pnum' 005/6:[----] [--] 'block/gluster: Do not force-cap *pnum' 006/6:[----] [--] 'block/iscsi: Do not force-cap *pnum' Max Reitz (6): block: Drop BDS comment regarding bdrv_append() block: block-status cache for data regions block: Clarify that @bytes is no limit on *pnum block/file-posix: Do not force-cap *pnum block/gluster: Do not force-cap *pnum block/iscsi: Do not force-cap *pnum include/block/block_int.h | 54 +++++++++++++++++++++++-- block.c | 84 +++++++++++++++++++++++++++++++++++++++ block/file-posix.c | 7 ++-- block/gluster.c | 7 ++-- block/io.c | 61 ++++++++++++++++++++++++++-- block/iscsi.c | 3 -- 6 files changed, 200 insertions(+), 16 deletions(-) Reviewed-by: Kevin Wolf