From patchwork Thu Sep 16 08:40:36 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hanna Czenczek X-Patchwork-Id: 12498291 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 19B46C433EF for ; Thu, 16 Sep 2021 08:47:57 +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 B492A61178 for ; Thu, 16 Sep 2021 08:47:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B492A61178 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:55396 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mQn3j-00072H-UI for qemu-devel@archiver.kernel.org; Thu, 16 Sep 2021 04:47:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48168) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mQmxQ-0004jU-8j for qemu-devel@nongnu.org; Thu, 16 Sep 2021 04:41:24 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:24753) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mQmxO-0004Gy-Mq for qemu-devel@nongnu.org; Thu, 16 Sep 2021 04:41:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631781681; 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=3XOocYzAQPSU4w9oDdGDlaI8wcduwC0/uQDUpjlWy54=; b=PcZiqASW1IFt9gJBreJ/ucjuoGGrYorhB1LWdtJXXN5J9pYLfYaZFaZeBb/o1k0F6hOAgH h5K3cAfn59J58Y/swzRS1K2i955IaG7obOnPHXFEZkc36t1gnihgCZ7l0kepKgHQm+xAed vuGAmqNwktLmbsr267v13oWg+thSYEI= 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-506-lQ9XCvOXNa2XCG3YHGwXyQ-1; Thu, 16 Sep 2021 04:41:20 -0400 X-MC-Unique: lQ9XCvOXNa2XCG3YHGwXyQ-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 C9FE819200C0 for ; Thu, 16 Sep 2021 08:41:19 +0000 (UTC) Received: from localhost (unknown [10.39.192.150]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 52EB460BD8; Thu, 16 Sep 2021 08:41:13 +0000 (UTC) From: Hanna Reitz To: qemu-devel@nongnu.org, virtio-fs@redhat.com Subject: [PATCH v4 03/12] virtiofsd: Add TempFd structure Date: Thu, 16 Sep 2021 10:40:36 +0200 Message-Id: <20210916084045.31684-4-hreitz@redhat.com> In-Reply-To: <20210916084045.31684-1-hreitz@redhat.com> References: <20210916084045.31684-1-hreitz@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=hreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=170.10.133.124; envelope-from=hreitz@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=-0.39, 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_H2=-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: Hanna Reitz , Stefan Hajnoczi , "Dr . David Alan Gilbert" , Vivek Goyal Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" We are planning to add file handles to lo_inode objects as an alternative to lo_inode.fd. That means that everywhere where we currently reference lo_inode.fd, we will have to open a temporary file descriptor that needs to be closed after use. So instead of directly accessing lo_inode.fd, there will be a helper function (lo_inode_fd()) that either returns lo_inode.fd, or opens a new file descriptor with open_by_handle_at(). It encapsulates this result in a TempFd structure to let the caller know whether the FD needs to be closed after use (opened from the handle) or not (copied from lo_inode.fd). By using g_auto(TempFd) to store this result, callers will not even have to care about closing a temporary FD after use. It will be done automatically once the object goes out of scope. Signed-off-by: Hanna Reitz --- tools/virtiofsd/passthrough_ll.c | 63 ++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index b43afdfbd3..88318a4ba9 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -180,6 +180,28 @@ struct lo_data { int user_posix_acl, posix_acl; }; +/** + * Represents a file descriptor that may either be owned by this + * TempFd, or only referenced (i.e. the ownership belongs to some + * other object, and the value has just been copied into this TempFd). + * + * The purpose of this encapsulation is to be used as g_auto(TempFd) + * to automatically clean up owned file descriptors when this object + * goes out of scope. + * + * Use temp_fd_steal() to get an owned file descriptor that will not + * be closed when the TempFd goes out of scope. + */ +typedef struct { + int fd; + bool owned; /* fd owned by this object? */ +} TempFd; + +#define TEMP_FD_INIT ((TempFd) { .fd = -1, .owned = false }) + +static void temp_fd_clear(TempFd *temp_fd); +G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(TempFd, temp_fd_clear); + static const struct fuse_opt lo_opts[] = { { "sandbox=namespace", offsetof(struct lo_data, sandbox), @@ -257,6 +279,47 @@ static struct lo_data *lo_data(fuse_req_t req) return (struct lo_data *)fuse_req_userdata(req); } +/** + * Clean-up function for TempFds + */ +static void temp_fd_clear(TempFd *temp_fd) +{ + if (temp_fd->owned) { + close(temp_fd->fd); + *temp_fd = TEMP_FD_INIT; + } +} + +/** + * Return an owned fd from *temp_fd that will not be closed when + * *temp_fd goes out of scope. + * + * (TODO: Remove __attribute__ once this is used.) + */ +static __attribute__((unused)) int temp_fd_steal(TempFd *temp_fd) +{ + if (temp_fd->owned) { + temp_fd->owned = false; + return temp_fd->fd; + } else { + return dup(temp_fd->fd); + } +} + +/** + * Create a borrowing copy of an existing TempFd. Note that *to is + * only valid as long as *from is valid. + * + * (TODO: Remove __attribute__ once this is used.) + */ +static __attribute__((unused)) void temp_fd_copy(const TempFd *from, TempFd *to) +{ + *to = (TempFd) { + .fd = from->fd, + .owned = false, + }; +} + /* * Load capng's state from our saved state if the current thread * hadn't previously been loaded.