From patchwork Thu Apr 20 11:37:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 1771282 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: legolas.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=eWtqm+Ap; dkim-atps=neutral Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4Q2G692cppz23tD for ; Thu, 20 Apr 2023 21:44:33 +1000 (AEST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ppSfi-0002Iz-Cr; Thu, 20 Apr 2023 07:41:54 -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 1ppSdH-0007xu-PT for qemu-devel@nongnu.org; Thu, 20 Apr 2023 07:39:27 -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 1ppSd3-0001fO-Rz for qemu-devel@nongnu.org; Thu, 20 Apr 2023 07:39:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1681990734; 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=svW5Iqq6ywfg5XGxDCHKSniKJYjg3etTmQ7BLHFrTFw=; b=eWtqm+ApRZ8T92cbiY/mfIE7agoUS3f17JekQJlS29ecG46Z1i50fPy8F5ir5EfyX8ha1/ +5w5M9rgkJsHNZwwT3UHiiQ5e+/39G2OhjCRk+aVp5PHguwYHcu0P8ybRylGMg6uFKyD9/ Mgd6/pyF1IItQv2JpH5j69Lo7y4QkDA= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-223-ugElyGhbO4WVcymr-LwNgg-1; Thu, 20 Apr 2023 07:38:51 -0400 X-MC-Unique: ugElyGhbO4WVcymr-LwNgg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 92E361C0897A; Thu, 20 Apr 2023 11:38:50 +0000 (UTC) Received: from localhost (unknown [10.39.193.254]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8A8FD51E3; Thu, 20 Apr 2023 11:38:49 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Peter Lieven , Stefan Hajnoczi , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , Paolo Bonzini , =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , Xie Yongji , Juan Quintela , qemu-block@nongnu.org, Eduardo Habkost , Richard Henderson , David Woodhouse , Stefan Weil , Fam Zheng , Julia Suvorova , Ronnie Sahlberg , xen-devel@lists.xenproject.org, Hanna Reitz , "Dr. David Alan Gilbert" , eesposit@redhat.com, Kevin Wolf , Marcel Apfelbaum , Stefano Stabellini , Paul Durrant , Aarushi Mehta , "Michael S. Tsirkin" , Anthony Perard , "Richard W.M. Jones" , Coiby Xu , Stefano Garzarella Subject: [PATCH v3 14/20] block/export: don't require AioContext lock around blk_exp_ref/unref() Date: Thu, 20 Apr 2023 07:37:26 -0400 Message-Id: <20230420113732.336620-15-stefanha@redhat.com> In-Reply-To: <20230420113732.336620-1-stefanha@redhat.com> References: <20230420113732.336620-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.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 e3fee60611..edb05c9268 100644 --- a/block/export/export.c +++ b/block/export/export.c @@ -201,11 +201,10 @@ 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 */ @@ -227,11 +226,10 @@ 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); @@ -339,7 +337,8 @@ 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 35dc8fcf45..611430afda 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); } }