From patchwork Thu May 4 19:53:21 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 13231738 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 9AE7BC7EE29 for ; Thu, 4 May 2023 19:59:34 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1puf1s-00060t-IT; Thu, 04 May 2023 15:54:16 -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 1puf1r-000608-3f for qemu-devel@nongnu.org; Thu, 04 May 2023 15:54:15 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1puf1p-0006Wc-JN for qemu-devel@nongnu.org; Thu, 04 May 2023 15:54:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1683230053; 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=bn7vYKIN4BAATa1eS0drL+2+35bJodnZI5fsBJiYTKs=; b=OSxaEwUd95m3Vo3PDEMVWkzx1/nMsrbwPEX0xIFpLe5xPpzFGB2DpwiVZGdhWG9P6w61Ig DxHPoN13aRbiosGaQ+v8TMYud3xbAFVGTUPe+9MmJOLHhcuJQNZyVNf7qwPylGHiIjtZou Sqc1LBL2NqiTSP1OATsWid5YZiEHPWE= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-94-EVERd-b1O6iV68LQZZKd_A-1; Thu, 04 May 2023 15:54:10 -0400 X-MC-Unique: EVERd-b1O6iV68LQZZKd_A-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id EC0B6A0F389; Thu, 4 May 2023 19:54:08 +0000 (UTC) Received: from localhost (unknown [10.39.192.57]) by smtp.corp.redhat.com (Postfix) with ESMTP id 51B294020960; Thu, 4 May 2023 19:54:08 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Ronnie Sahlberg , Aarushi Mehta , qemu-block@nongnu.org, Paul Durrant , Anthony Perard , Peter Lieven , Stefan Weil , Xie Yongji , Kevin Wolf , Paolo Bonzini , "Michael S. Tsirkin" , Leonardo Bras , Peter Xu , Hanna Reitz , Stefano Stabellini , Richard Henderson , David Woodhouse , Coiby Xu , Eduardo Habkost , Stefano Garzarella , =?utf-8?q?Philippe_Mathieu-Daud?= =?utf-8?q?=C3=A9?= , =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , Stefan Hajnoczi , Julia Suvorova , xen-devel@lists.xenproject.org, eesposit@redhat.com, Juan Quintela , "Richard W.M. Jones" , Fam Zheng , Marcel Apfelbaum Subject: [PATCH v5 15/21] block/export: don't require AioContext lock around blk_exp_ref/unref() Date: Thu, 4 May 2023 15:53:21 -0400 Message-Id: <20230504195327.695107-16-stefanha@redhat.com> In-Reply-To: <20230504195327.695107-1-stefanha@redhat.com> References: <20230504195327.695107-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.161, 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org The FUSE export calls blk_exp_ref/unref() without the AioContext lock. Instead of fixing the FUSE export, adjust blk_exp_ref/unref() so they work without the AioContext lock. This way it's less error-prone. Suggested-by: Paolo Bonzini Signed-off-by: Stefan Hajnoczi --- include/block/export.h | 2 ++ block/export/export.c | 13 ++++++------- block/export/vduse-blk.c | 4 ---- 3 files changed, 8 insertions(+), 11 deletions(-) diff --git a/include/block/export.h b/include/block/export.h index 7feb02e10d..f2fe0f8078 100644 --- a/include/block/export.h +++ b/include/block/export.h @@ -57,6 +57,8 @@ struct BlockExport { * Reference count for this block export. This includes strong references * both from the owner (qemu-nbd or the monitor) and clients connected to * the export. + * + * Use atomics to access this field. */ int refcount; diff --git a/block/export/export.c b/block/export/export.c index 62c7c22d45..ab007e9d31 100644 --- a/block/export/export.c +++ b/block/export/export.c @@ -202,11 +202,10 @@ fail: return NULL; } -/* Callers must hold exp->ctx lock */ void blk_exp_ref(BlockExport *exp) { - assert(exp->refcount > 0); - exp->refcount++; + assert(qatomic_read(&exp->refcount) > 0); + qatomic_inc(&exp->refcount); } /* Runs in the main thread */ @@ -229,11 +228,10 @@ static void blk_exp_delete_bh(void *opaque) aio_context_release(aio_context); } -/* Callers must hold exp->ctx lock */ void blk_exp_unref(BlockExport *exp) { - assert(exp->refcount > 0); - if (--exp->refcount == 0) { + assert(qatomic_read(&exp->refcount) > 0); + if (qatomic_fetch_dec(&exp->refcount) == 1) { /* Touch the block_exports list only in the main thread */ aio_bh_schedule_oneshot(qemu_get_aio_context(), blk_exp_delete_bh, exp); @@ -341,7 +339,8 @@ void qmp_block_export_del(const char *id, if (!has_mode) { mode = BLOCK_EXPORT_REMOVE_MODE_SAFE; } - if (mode == BLOCK_EXPORT_REMOVE_MODE_SAFE && exp->refcount > 1) { + if (mode == BLOCK_EXPORT_REMOVE_MODE_SAFE && + qatomic_read(&exp->refcount) > 1) { error_setg(errp, "export '%s' still in use", exp->id); error_append_hint(errp, "Use mode='hard' to force client " "disconnect\n"); diff --git a/block/export/vduse-blk.c b/block/export/vduse-blk.c index a25556fe04..e0455551f9 100644 --- a/block/export/vduse-blk.c +++ b/block/export/vduse-blk.c @@ -44,9 +44,7 @@ static void vduse_blk_inflight_inc(VduseBlkExport *vblk_exp) { if (qatomic_fetch_inc(&vblk_exp->inflight) == 0) { /* Prevent export from being deleted */ - aio_context_acquire(vblk_exp->export.ctx); blk_exp_ref(&vblk_exp->export); - aio_context_release(vblk_exp->export.ctx); } } @@ -57,9 +55,7 @@ static void vduse_blk_inflight_dec(VduseBlkExport *vblk_exp) aio_wait_kick(); /* Now the export can be deleted */ - aio_context_acquire(vblk_exp->export.ctx); blk_exp_unref(&vblk_exp->export); - aio_context_release(vblk_exp->export.ctx); } }