From patchwork Fri Oct 27 15:53:24 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 13455681 Received: from list by lists.gnu.org with archive (Exim 4.90_1) id 1qwPAO-0005F2-GV for mharc-qemu-devel@gnu.org; Fri, 27 Oct 2023 11:54:32 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qwPA8-0003hL-DX for qemu-devel@nongnu.org; Fri, 27 Oct 2023 11:54:16 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qwPA0-0002ql-9d for qemu-devel@nongnu.org; Fri, 27 Oct 2023 11:54:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1698422046; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gpL/KtmpVIqThlM8BLmlN6PH2UjUT2DtdwR9cJu4xJs=; b=BEHR8HPACxRw0vGaUch4WSmnIX15wKmP6SmXex+4JxAhNACyHMSsqQVQXPhRmxDhvSR4S8 fv+RbyrtQ/bm8vKlavX8Ry+If1Ba3SgYHyjsq4lOG5/lDH/EL1V3paOssjHFeF8GAARw0G eFxZZANqBfF5hNv71k4nFXo9twDvRDY= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-471-REorJkxLOeCmvFk5mNRDEw-1; Fri, 27 Oct 2023 11:54:03 -0400 X-MC-Unique: REorJkxLOeCmvFk5mNRDEw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D9069101A52D; Fri, 27 Oct 2023 15:54:02 +0000 (UTC) Received: from merkur.fritz.box (unknown [10.39.194.78]) by smtp.corp.redhat.com (Postfix) with ESMTP id AAFE05027; Fri, 27 Oct 2023 15:54:01 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, stefanha@redhat.com, eesposit@redhat.com, eblake@redhat.com, pbonzini@redhat.com, vsementsov@yandex-team.ru, qemu-devel@nongnu.org Subject: [PATCH 15/24] block: Mark bdrv_replace_node_common() GRAPH_WRLOCK Date: Fri, 27 Oct 2023 17:53:24 +0200 Message-ID: <20231027155333.420094-16-kwolf@redhat.com> In-Reply-To: <20231027155333.420094-1-kwolf@redhat.com> References: <20231027155333.420094-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 27 Oct 2023 15:54:17 -0000 Instead of taking the writer lock internally, require callers to already hold it when calling bdrv_replace_node_common(). Basically everthing in the function needs the lock and its callers may already want to hold the graph lock and so wouldn't be able to call functions that take it internally. Signed-off-by: Kevin Wolf --- block.c | 68 ++++++++++++++++++++++++++++++++++++--------------------- 1 file changed, 43 insertions(+), 25 deletions(-) diff --git a/block.c b/block.c index dc43e36f69..c7409cf658 100644 --- a/block.c +++ b/block.c @@ -5412,6 +5412,9 @@ bdrv_replace_node_noperm(BlockDriverState *from, } /* + * Switch all parents of @from to point to @to instead. @from and @to must be in + * the same AioContext and both must be drained. + * * With auto_skip=true bdrv_replace_node_common skips updating from parents * if it creates a parent-child relation loop or if parent is block-job. * @@ -5421,10 +5424,9 @@ bdrv_replace_node_noperm(BlockDriverState *from, * With @detach_subchain=true @to must be in a backing chain of @from. In this * case backing link of the cow-parent of @to is removed. */ -static int bdrv_replace_node_common(BlockDriverState *from, - BlockDriverState *to, - bool auto_skip, bool detach_subchain, - Error **errp) +static int GRAPH_WRLOCK +bdrv_replace_node_common(BlockDriverState *from, BlockDriverState *to, + bool auto_skip, bool detach_subchain, Error **errp) { Transaction *tran = tran_new(); g_autoptr(GSList) refresh_list = NULL; @@ -5433,16 +5435,9 @@ static int bdrv_replace_node_common(BlockDriverState *from, GLOBAL_STATE_CODE(); - /* Make sure that @from doesn't go away until we have successfully attached - * all of its parents to @to. */ - bdrv_ref(from); - - assert(qemu_get_current_aio_context() == qemu_get_aio_context()); + assert(from->quiesce_counter); + assert(to->quiesce_counter); assert(bdrv_get_aio_context(from) == bdrv_get_aio_context(to)); - bdrv_drained_begin(from); - bdrv_drained_begin(to); - - bdrv_graph_wrlock(to); if (detach_subchain) { assert(bdrv_chain_contains(from, to)); @@ -5483,33 +5478,51 @@ static int bdrv_replace_node_common(BlockDriverState *from, out: tran_finalize(tran, ret); - bdrv_graph_wrunlock(); - - bdrv_drained_end(to); - bdrv_drained_end(from); - bdrv_unref(from); - return ret; } int bdrv_replace_node(BlockDriverState *from, BlockDriverState *to, Error **errp) { + int ret; + GLOBAL_STATE_CODE(); - return bdrv_replace_node_common(from, to, true, false, errp); + /* Make sure that @from doesn't go away until we have successfully attached + * all of its parents to @to. */ + bdrv_ref(from); + bdrv_drained_begin(from); + bdrv_drained_begin(to); + bdrv_graph_wrlock(to); + + ret = bdrv_replace_node_common(from, to, true, false, errp); + + bdrv_graph_wrunlock(); + bdrv_drained_end(to); + bdrv_drained_end(from); + bdrv_unref(from); + + return ret; } int bdrv_drop_filter(BlockDriverState *bs, Error **errp) { BlockDriverState *child_bs; + int ret; GLOBAL_STATE_CODE(); + bdrv_graph_rdlock_main_loop(); child_bs = bdrv_filter_or_cow_bs(bs); bdrv_graph_rdunlock_main_loop(); - return bdrv_replace_node_common(bs, child_bs, true, true, errp); + bdrv_drained_begin(child_bs); + bdrv_graph_wrlock(bs); + ret = bdrv_replace_node_common(bs, child_bs, true, true, errp); + bdrv_graph_wrunlock(); + bdrv_drained_end(child_bs); + + return ret; } /* @@ -5957,15 +5970,15 @@ int bdrv_drop_intermediate(BlockDriverState *top, BlockDriverState *base, bdrv_ref(top); bdrv_drained_begin(base); - bdrv_graph_rdlock_main_loop(); + bdrv_graph_wrlock(base); if (!top->drv || !base->drv) { - goto exit; + goto exit_wrlock; } /* Make sure that base is in the backing chain of top */ if (!bdrv_chain_contains(top, base)) { - goto exit; + goto exit_wrlock; } /* If 'base' recursively inherits from 'top' then we should set @@ -5997,6 +6010,8 @@ int bdrv_drop_intermediate(BlockDriverState *top, BlockDriverState *base, * That's a FIXME. */ bdrv_replace_node_common(top, base, false, false, &local_err); + bdrv_graph_wrunlock(); + if (local_err) { error_report_err(local_err); goto exit; @@ -6029,8 +6044,11 @@ int bdrv_drop_intermediate(BlockDriverState *top, BlockDriverState *base, } ret = 0; + goto exit; + +exit_wrlock: + bdrv_graph_wrunlock(); exit: - bdrv_graph_rdunlock_main_loop(); bdrv_drained_end(base); bdrv_unref(top); return ret;