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bh=Ig6Kp3mWpMrAooTlxwoFNFxHos9nMIFoJHer2183q+g=; b=ADd+13iXWcVAw2IDi91hVxGa/1tbjM30gFzWPBy/GUu6EL4H9KlCNh71Mr+Idxu2c8StzS vxffuCK3Th6azXgIxkhxjolEPyLOy5aC0QfVGqpAzdQG4Pfi0RX0lg4lziSCX/EtCcAaYW x72z9Xo2OllLKnUGofRNNajS6G/8DOs= 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-407-RTAw8xEhNJOtOH2Dn-kzMQ-1; Thu, 14 Jan 2021 13:01:01 -0500 X-MC-Unique: RTAw8xEhNJOtOH2Dn-kzMQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id CD4A9100A679; Thu, 14 Jan 2021 18:00:45 +0000 (UTC) Received: from redhat.com (ovpn-112-150.ams2.redhat.com [10.36.112.150]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 879A150F7D; Thu, 14 Jan 2021 18:00:38 +0000 (UTC) Date: Thu, 14 Jan 2021 18:00:35 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Jag Raman Subject: Re: [PATCH v19 08/20] io: add qio_channel_readv_full_all_eof & qio_channel_readv_full_all helpers Message-ID: <20210114180035.GY1643043@redhat.com> References: <02a82c80a35ab60b98028c85aa94f688a2843943.1610638428.git.jag.raman@oracle.com> <20210114162729.GB306329@stefanha-x1.localdomain> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.248, 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_H3=0.001, RCVD_IN_MSPIKE_WL=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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Elena Ufimtseva , Fam Zheng , Swapnil Ingle , John G Johnson , qemu-level , kraxel@redhat.com, quintela@redhat.com, mst@redhat.com, armbru@redhat.com, kanth.ghatraju@oracle.com, felipe@nutanix.com, thuth@redhat.com, ehabkost@redhat.com, konrad.wilk@oracle.com, dgilbert@redhat.com, alex.williamson@redhat.com, Stefan Hajnoczi , pbonzini@redhat.com, kwolf@redhat.com, mreitz@redhat.com, ross.lagerwall@citrix.com, marcandre.lureau@gmail.com, thanos.makatos@nutanix.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jan 14, 2021 at 12:55:58PM -0500, Jag Raman wrote: > > > > On Jan 14, 2021, at 11:27 AM, Stefan Hajnoczi wrote: > > > > On Thu, Jan 14, 2021 at 10:40:03AM -0500, Jagannathan Raman wrote: > >> +int qio_channel_readv_full_all(QIOChannel *ioc, > >> + const struct iovec *iov, > >> + size_t niov, > >> + int **fds, size_t *nfds, > >> + Error **errp) > >> { > >> - int ret = qio_channel_readv_all_eof(ioc, iov, niov, errp); > >> + int ret = qio_channel_readv_full_all_eof(ioc, iov, niov, fds, nfds, errp); > >> > >> if (ret == 0) { > >> - ret = -1; > >> error_setg(errp, > >> "Unexpected end-of-file before all bytes were read"); > > > > qio_channel_readv_full_all_eof() can read file descriptors but no data > > and return 0. > > > > Here that case is converted into an error and the file descriptors > > aren't closed, freed, and fds/nfds isn't cleared. > > That’s a valid point. I’m wondering if the fix for this case should be in > qio_channel_readv_full_all_eof(), instead of here. > > qio_channel_readv_full_all_eof() should probably return error (-1) if the > amount of data read does not match iov_size(). If the caller is only expecting > to read fds, and not any data, it would indicate that by setting iov to NULL > and/or setting niov=0. If the caller is setting these parameters, it means it is > expecting data.Does that sound good? The API spec for the existing _eof() methods says: * The function will wait for all requested data * to be read, yielding from the current coroutine * if required. * * If end-of-file occurs before any data is read, * no error is reported; otherwise, if it occurs * before all requested data has been read, an error * will be reported. IOW, return '0' is *only* valid if we've not read anything. I consider file descriptors to be something. IOW, qio_channel_readv_full_all_eof must only return 0, if it didn't read any data and also didn't receive any file descriptors. So yeah, we must return -1 in the scenario Stefan describes Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|