From mboxrd@z Thu Jan 1 00:00:00 1970 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 4A6BCC4338F for ; Fri, 6 Aug 2021 14:42:29 +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 A05CD6052B for ; Fri, 6 Aug 2021 14:42:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org A05CD6052B 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]:60658 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mC13L-0005YU-CF for qemu-devel@archiver.kernel.org; Fri, 06 Aug 2021 10:42:27 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:36706) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mC12S-0004rH-HH for qemu-devel@nongnu.org; Fri, 06 Aug 2021 10:41:33 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:52964) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mC12M-0004YZ-U0 for qemu-devel@nongnu.org; Fri, 06 Aug 2021 10:41:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628260886; 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: in-reply-to:in-reply-to:references:references; bh=juEptnuIAWmj3jej4+9h8pTjOZUkXLeJyivC5KTG55s=; b=YG76inly+9cCP3zPe2pUUn27w5Nf6uhMNbw3nXomw91lsAUfVbgdFlFYNC0utgj8IyRL22 SFhsU/bHZc7HNQoif0ZZkz6PsNXTKUYihuo9IBfqZRzWf3OGpcmJTXM2EEI3PCuy1DH3jR /Ep8lvCWyJpV/RHh+ksCs09ZRKqYyZg= 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-469-EwDb-oz4MzmLT3rofh_n4Q-1; Fri, 06 Aug 2021 10:41:24 -0400 X-MC-Unique: EwDb-oz4MzmLT3rofh_n4Q-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C477A871803 for ; Fri, 6 Aug 2021 14:41:23 +0000 (UTC) Received: from horse.redhat.com (unknown [10.22.18.7]) by smtp.corp.redhat.com (Postfix) with ESMTP id 39B435C1A3; Fri, 6 Aug 2021 14:41:16 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id A5462220261; Fri, 6 Aug 2021 10:41:15 -0400 (EDT) Date: Fri, 6 Aug 2021 10:41:15 -0400 From: Vivek Goyal To: Max Reitz Subject: Re: [PATCH v3 02/10] virtiofsd: Add TempFd structure Message-ID: References: <20210730150134.216126-1-mreitz@redhat.com> <20210730150134.216126-3-mreitz@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210730150134.216126-3-mreitz@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=vgoyal@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=vgoyal@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.7, 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: virtio-fs@redhat.com, qemu-devel@nongnu.org, Stefan Hajnoczi , "Dr . David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Jul 30, 2021 at 05:01:26PM +0200, Max Reitz wrote: > 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). I am wondering why this notion of "owned". Why not have this requirement of always closing "fd". If we copied it from lo_inode.fd, then we will need to dup() it. Otherwise we opened it from file handle and we will need to close it anyway. I guess you are trying to avoid having to call dup() and that's why this notion of "owned" 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: Max Reitz > Reviewed-by: Connor Kuehl > --- > tools/virtiofsd/passthrough_ll.c | 49 ++++++++++++++++++++++++++++++++ > 1 file changed, 49 insertions(+) > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index 1f27eeabc5..fb5e073e6a 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -178,6 +178,28 @@ 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), > @@ -255,6 +277,33 @@ 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); > + } > +} This also will be simpler if we always called dup() and every caller will close() fd. I think only downside is having to call dup()/close(). Not sure if this is an expensive operation or not. Vivek From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 6 Aug 2021 10:41:15 -0400 From: Vivek Goyal Message-ID: References: <20210730150134.216126-1-mreitz@redhat.com> <20210730150134.216126-3-mreitz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210730150134.216126-3-mreitz@redhat.com> Subject: Re: [Virtio-fs] [PATCH v3 02/10] virtiofsd: Add TempFd structure List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org On Fri, Jul 30, 2021 at 05:01:26PM +0200, Max Reitz wrote: > 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). I am wondering why this notion of "owned". Why not have this requirement of always closing "fd". If we copied it from lo_inode.fd, then we will need to dup() it. Otherwise we opened it from file handle and we will need to close it anyway. I guess you are trying to avoid having to call dup() and that's why this notion of "owned" 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: Max Reitz > Reviewed-by: Connor Kuehl > --- > tools/virtiofsd/passthrough_ll.c | 49 ++++++++++++++++++++++++++++++++ > 1 file changed, 49 insertions(+) > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index 1f27eeabc5..fb5e073e6a 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -178,6 +178,28 @@ 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), > @@ -255,6 +277,33 @@ 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); > + } > +} This also will be simpler if we always called dup() and every caller will close() fd. I think only downside is having to call dup()/close(). Not sure if this is an expensive operation or not. Vivek