From patchwork Tue Jun 1 05:57:28 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergio Lopez X-Patchwork-Id: 12290455 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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,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 27D66C4708F for ; Tue, 1 Jun 2021 06:00:34 +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 98FAF61263 for ; Tue, 1 Jun 2021 06:00:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 98FAF61263 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]:36692 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lnxS4-0004YG-OM for qemu-devel@archiver.kernel.org; Tue, 01 Jun 2021 02:00:32 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57840) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lnxPP-0008Ae-L8 for qemu-devel@nongnu.org; Tue, 01 Jun 2021 01:57:47 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:22264) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lnxPN-00023i-Ex for qemu-devel@nongnu.org; Tue, 01 Jun 2021 01:57:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622527064; 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=/O6nN7HyWGO9hGQpiIgOSJ/l5K5+rWXv4rWS9qdlYJI=; b=YcHMISx7fSfJbgjv+aETbkfqVgMiBH5WIGZiuxAl/ee5bI+mLQE9wUkL3y40EQ1fx6ISPx 6aqk292vXNnc66jzxu8lVmg6DEW/7NngTqM3QOe89aH1k4Pe+t40uQxHREkJ8+SsQQDf9p 7/Ngy1DuyfkWPPPx8Lw8r4u0PmSqvck= 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-443-rXbLyQ_aPX--9izAQt0OTA-1; Tue, 01 Jun 2021 01:57:42 -0400 X-MC-Unique: rXbLyQ_aPX--9izAQt0OTA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C82D5800D55; Tue, 1 Jun 2021 05:57:41 +0000 (UTC) Received: from toolbox.redhat.com (unknown [10.33.36.16]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1208369FA4; Tue, 1 Jun 2021 05:57:39 +0000 (UTC) From: Sergio Lopez To: qemu-devel@nongnu.org Subject: [PATCH 2/2] nbd/server: Use drained block ops to quiesce the server Date: Tue, 1 Jun 2021 07:57:28 +0200 Message-Id: <20210601055728.90849-3-slp@redhat.com> In-Reply-To: <20210601055728.90849-1-slp@redhat.com> References: <20210601055728.90849-1-slp@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=slp@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=slp@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=-0.372, 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=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 , Sergio Lopez , qemu-block@nongnu.org, Max Reitz , Nir Soffer Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Before switching between AioContexts we need to make sure that we're fully quiesced ("nb_requests == 0" for every client) when entering the drained section. To do this, we set "quiescing = true" for every client on ".drained_begin" to prevent new coroutines to be created, and check if "nb_requests == 0" on ".drained_poll". Finally, once we're exiting the drained section, on ".drained_end" we set "quiescing = false" and call "nbd_client_receive_next_request()" to resume the processing of new requests. With these changes, "blk_aio_attach()" and "blk_aio_detach()" can be reverted to be as simple as they were before f148ae7d36. RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1960137 Suggested-by: Kevin Wolf Signed-off-by: Sergio Lopez --- nbd/server.c | 99 +++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 75 insertions(+), 24 deletions(-) diff --git a/nbd/server.c b/nbd/server.c index 86a44a9b41..33e55479d7 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -132,7 +132,7 @@ struct NBDClient { CoMutex send_lock; Coroutine *send_coroutine; - bool read_yielding; + GSList *yield_co_list; /* List of coroutines yielding on nbd_read_eof */ bool quiescing; QTAILQ_ENTRY(NBDClient) next; @@ -1367,6 +1367,7 @@ static inline int coroutine_fn nbd_read_eof(NBDClient *client, void *buffer, size_t size, Error **errp) { bool partial = false; + Coroutine *co; assert(size); while (size > 0) { @@ -1375,9 +1376,12 @@ nbd_read_eof(NBDClient *client, void *buffer, size_t size, Error **errp) len = qio_channel_readv(client->ioc, &iov, 1, errp); if (len == QIO_CHANNEL_ERR_BLOCK) { - client->read_yielding = true; + co = qemu_coroutine_self(); + + client->yield_co_list = g_slist_prepend(client->yield_co_list, co); qio_channel_yield(client->ioc, G_IO_IN); - client->read_yielding = false; + client->yield_co_list = g_slist_remove(client->yield_co_list, co); + if (client->quiescing) { return -EAGAIN; } @@ -1513,6 +1517,11 @@ static void nbd_request_put(NBDRequestData *req) g_free(req); client->nb_requests--; + + if (client->quiescing && client->nb_requests == 0) { + aio_wait_kick(); + } + nbd_client_receive_next_request(client); nbd_client_put(client); @@ -1530,49 +1539,75 @@ static void blk_aio_attached(AioContext *ctx, void *opaque) QTAILQ_FOREACH(client, &exp->clients, next) { qio_channel_attach_aio_context(client->ioc, ctx); + assert(client->nb_requests == 0); assert(client->recv_coroutine == NULL); assert(client->send_coroutine == NULL); - - if (client->quiescing) { - client->quiescing = false; - nbd_client_receive_next_request(client); - } } } -static void nbd_aio_detach_bh(void *opaque) +static void blk_aio_detach(void *opaque) { NBDExport *exp = opaque; NBDClient *client; + trace_nbd_blk_aio_detach(exp->name, exp->common.ctx); + QTAILQ_FOREACH(client, &exp->clients, next) { qio_channel_detach_aio_context(client->ioc); + } + + exp->common.ctx = NULL; +} + +static void nbd_drained_begin(void *opaque) +{ + NBDExport *exp = opaque; + NBDClient *client; + + QTAILQ_FOREACH(client, &exp->clients, next) { client->quiescing = true; + } +} - if (client->recv_coroutine) { - if (client->read_yielding) { - qemu_aio_coroutine_enter(exp->common.ctx, - client->recv_coroutine); - } else { - AIO_WAIT_WHILE(exp->common.ctx, client->recv_coroutine != NULL); - } - } +static void nbd_drained_end(void *opaque) +{ + NBDExport *exp = opaque; + NBDClient *client; - if (client->send_coroutine) { - AIO_WAIT_WHILE(exp->common.ctx, client->send_coroutine != NULL); - } + QTAILQ_FOREACH(client, &exp->clients, next) { + client->quiescing = false; + nbd_client_receive_next_request(client); } } -static void blk_aio_detach(void *opaque) +static bool nbd_drained_poll(void *opaque) { NBDExport *exp = opaque; + NBDClient *client; + Coroutine *co; + GSList *entry; + GSList *coroutine_list; - trace_nbd_blk_aio_detach(exp->name, exp->common.ctx); + QTAILQ_FOREACH(client, &exp->clients, next) { + if (client->nb_requests != 0) { + /* + * Enter coroutines waiting for new requests on nbd_read_eof(), so + * we don't depend on the client to wake us up. + */ + coroutine_list = g_slist_copy(client->yield_co_list); + for (entry = coroutine_list; + entry != NULL; + entry = g_slist_next(entry)) { + co = entry->data; + qemu_aio_coroutine_enter(exp->common.ctx, co); + } + g_slist_free(coroutine_list); - aio_wait_bh_oneshot(exp->common.ctx, nbd_aio_detach_bh, exp); + return 1; + } + } - exp->common.ctx = NULL; + return 0; } static void nbd_eject_notifier(Notifier *n, void *data) @@ -1594,6 +1629,12 @@ void nbd_export_set_on_eject_blk(BlockExport *exp, BlockBackend *blk) blk_add_remove_bs_notifier(blk, &nbd_exp->eject_notifier); } +static const BlockDevOps nbd_block_ops = { + .drained_begin = nbd_drained_begin, + .drained_end = nbd_drained_end, + .drained_poll = nbd_drained_poll, +}; + static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args, Error **errp) { @@ -1715,8 +1756,17 @@ static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args, exp->allocation_depth = arg->allocation_depth; + /* + * We need to inhibit request queuing in the block layer to ensure we can + * be properly quiesced when entering a drained section, as our coroutines + * servicing pending requests might enter blk_pread(). + */ + blk_set_disable_request_queuing(blk, true); + blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp); + blk_set_dev_ops(blk, &nbd_block_ops, exp); + QTAILQ_INSERT_TAIL(&exports, exp, next); return 0; @@ -1788,6 +1838,7 @@ static void nbd_export_delete(BlockExport *blk_exp) } blk_remove_aio_context_notifier(exp->common.blk, blk_aio_attached, blk_aio_detach, exp); + blk_set_disable_request_queuing(exp->common.blk, false); } for (i = 0; i < exp->nr_export_bitmaps; i++) {