From patchwork Thu Dec 12 16:39:04 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: "Dr. David Alan Gilbert" X-Patchwork-Id: 11288965 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0837A6C1 for ; Thu, 12 Dec 2019 18:01:23 +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 C9852206DA for ; Thu, 12 Dec 2019 18:01:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Ox678Zcm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C9852206DA 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+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:35164 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ifSm9-00079v-RC for patchwork-qemu-devel@patchwork.kernel.org; Thu, 12 Dec 2019 13:01:22 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:40067) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ifRXH-00088s-KB for qemu-devel@nongnu.org; Thu, 12 Dec 2019 11:41:56 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ifRXG-0005Ix-B7 for qemu-devel@nongnu.org; Thu, 12 Dec 2019 11:41:55 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:30430 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ifRXG-0005Hx-6v for qemu-devel@nongnu.org; Thu, 12 Dec 2019 11:41:54 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576168913; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Xe0Smz7KCQ1tatJhdpkcqF38kefQFyt1PnKLRIic9VM=; b=Ox678Zcm3W30XTIULXzipEAXhRYIFkmj0PUuM4I4BDnriFFlx3G5xLkKn9fnSQsOhH1io5 5IovWGvGFmiUzQOGSjRoDKAAcDAGiPU9sKKC/ADWKKsWrpN6nIuJIDsDYFFIqJf1loBCvw +G84g7lkACFA8xEoyFC2W6JFxJSKYS4= 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-2-39LhyZhmOcKAqfm8G6Cq2Q-1; Thu, 12 Dec 2019 11:41:50 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A9EE9107ACC4 for ; Thu, 12 Dec 2019 16:41:48 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-116-226.ams2.redhat.com [10.36.116.226]) by smtp.corp.redhat.com (Postfix) with ESMTP id CF27660BE1; Thu, 12 Dec 2019 16:41:47 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com Subject: [PATCH 104/104] virtiofsd: Convert lo_destroy to take the lo->mutex lock itself Date: Thu, 12 Dec 2019 16:39:04 +0000 Message-Id: <20191212163904.159893-105-dgilbert@redhat.com> In-Reply-To: <20191212163904.159893-1-dgilbert@redhat.com> References: <20191212163904.159893-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: 39LhyZhmOcKAqfm8G6Cq2Q-1 X-Mimecast-Spam-Score: 0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.61 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: , Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" From: "Dr. David Alan Gilbert" lo_destroy was relying on some implicit knowledge of the locking; we can avoid this if we create an unref_inode that doesn't take the lock and then grab it for the whole of the lo_destroy. Suggested-by: Vivek Goyal Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Philippe Mathieu-Daudé --- tools/virtiofsd/passthrough_ll.c | 31 +++++++++++++++++-------------- 1 file changed, 17 insertions(+), 14 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index 38f4948e61..c37f57157e 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -1328,14 +1328,13 @@ static void lo_unlink(fuse_req_t req, fuse_ino_t parent, const char *name) lo_inode_put(lo, &inode); } -static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode, - uint64_t n) +/* To be called with lo->mutex held */ +static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64_t n) { if (!inode) { return; } - pthread_mutex_lock(&lo->mutex); assert(inode->nlookup >= n); inode->nlookup -= n; if (!inode->nlookup) { @@ -1346,15 +1345,24 @@ static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode, } g_hash_table_destroy(inode->posix_locks); pthread_mutex_destroy(&inode->plock_mutex); - pthread_mutex_unlock(&lo->mutex); /* Drop our refcount from lo_do_lookup() */ lo_inode_put(lo, &inode); - } else { - pthread_mutex_unlock(&lo->mutex); } } +static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode, + uint64_t n) +{ + if (!inode) { + return; + } + + pthread_mutex_lock(&lo->mutex); + unref_inode(lo, inode, n); + pthread_mutex_unlock(&lo->mutex); +} + static void lo_forget_one(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup) { struct lo_data *lo = lo_data(req); @@ -2441,13 +2449,7 @@ static void lo_destroy(void *userdata) { struct lo_data *lo = (struct lo_data *)userdata; - /* - * Normally lo->mutex must be taken when traversing lo->inodes but - * lo_destroy() is a serialized request so no races are possible here. - * - * In addition, we cannot acquire lo->mutex since unref_inode() takes it - * too and this would result in a recursive lock. - */ + pthread_mutex_lock(&lo->mutex); while (true) { GHashTableIter iter; gpointer key, value; @@ -2458,8 +2460,9 @@ static void lo_destroy(void *userdata) } struct lo_inode *inode = value; - unref_inode_lolocked(lo, inode, inode->nlookup); + unref_inode(lo, inode, inode->nlookup); } + pthread_mutex_unlock(&lo->mutex); } static struct fuse_lowlevel_ops lo_oper = {