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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 4245DC47258 for ; Wed, 17 Jan 2024 12:40:02 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rQ5Cl-0002XS-4O; Wed, 17 Jan 2024 07:39:39 -0500 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 1rQ5Ck-0002XC-79 for qemu-devel@nongnu.org; Wed, 17 Jan 2024 07:39:38 -0500 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 1rQ5Ci-0001p2-A4 for qemu-devel@nongnu.org; Wed, 17 Jan 2024 07:39:37 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1705495175; h=from:from:reply-to: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=J22K0ldcYzUYnmiaIuWPAHKIET3Cyer2F9SJFl6XWbo=; b=cG9NMsYtWHp3UZ2OgF5ioMb5zucA7HUlqU2c4Rt9se28ek05GLIytZbqves2izDlVxPD4l 46Z/QG++YGeLS4fb06C4Cfzrv31z2KEntd5s2hgBAxtCZXsWGy3LCHieN0tEJR7RRPohe4 sZtllpvOsy9iLPMbQGoJzYVfcajOF3A= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-615-XDoHvDtBN5-62plRYVAEFQ-1; Wed, 17 Jan 2024 07:39:29 -0500 X-MC-Unique: XDoHvDtBN5-62plRYVAEFQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 518C2800076; Wed, 17 Jan 2024 12:39:29 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.167]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3E12AC15A0C; Wed, 17 Jan 2024 12:39:28 +0000 (UTC) Date: Wed, 17 Jan 2024 12:39:26 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Fabiano Rosas Cc: qemu-devel@nongnu.org, armbru@redhat.com, Juan Quintela , Peter Xu , Leonardo Bras , Claudio Fontana Subject: Re: [RFC PATCH v3 15/30] io: Add a pwritev/preadv version that takes a discontiguous iovec Message-ID: References: <20231127202612.23012-1-farosas@suse.de> <20231127202612.23012-16-farosas@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20231127202612.23012-16-farosas@suse.de> User-Agent: Mutt/2.2.10 (2023-03-25) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -38 X-Spam_score: -3.9 X-Spam_bar: --- X-Spam_report: (-3.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.806, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Nov 27, 2023 at 05:25:57PM -0300, Fabiano Rosas wrote: > For the upcoming support to fixed-ram migration with multifd, we need > to be able to accept an iovec array with non-contiguous data. > > Add a pwritev and preadv version that splits the array into contiguous > segments before writing. With that we can have the ram code continue > to add pages in any order and the multifd code continue to send large > arrays for reading and writing. > > Signed-off-by: Fabiano Rosas > --- > - split the API that was merged into a single function > - use uintptr_t for compatibility with 32-bit > --- > include/io/channel.h | 26 ++++++++++++++++ > io/channel.c | 70 ++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 96 insertions(+) > > diff --git a/include/io/channel.h b/include/io/channel.h > index 7986c49c71..25383db5aa 100644 > --- a/include/io/channel.h > +++ b/include/io/channel.h > @@ -559,6 +559,19 @@ int qio_channel_close(QIOChannel *ioc, > ssize_t qio_channel_pwritev(QIOChannel *ioc, const struct iovec *iov, > size_t niov, off_t offset, Error **errp); > > +/** > + * qio_channel_pwritev_all: > + * @ioc: the channel object > + * @iov: the array of memory regions to write data from > + * @niov: the length of the @iov array > + * @offset: the iovec offset in the file where to write the data > + * @errp: pointer to a NULL-initialized error object > + * > + * Returns: 0 if all bytes were written, or -1 on error > + */ > +int qio_channel_pwritev_all(QIOChannel *ioc, const struct iovec *iov, > + size_t niov, off_t offset, Error **errp); > + > /** > * qio_channel_pwrite > * @ioc: the channel object > @@ -595,6 +608,19 @@ ssize_t qio_channel_pwrite(QIOChannel *ioc, char *buf, size_t buflen, > ssize_t qio_channel_preadv(QIOChannel *ioc, const struct iovec *iov, > size_t niov, off_t offset, Error **errp); > > +/** > + * qio_channel_preadv_all: > + * @ioc: the channel object > + * @iov: the array of memory regions to read data to > + * @niov: the length of the @iov array > + * @offset: the iovec offset in the file from where to read the data > + * @errp: pointer to a NULL-initialized error object > + * > + * Returns: 0 if all bytes were read, or -1 on error > + */ > +int qio_channel_preadv_all(QIOChannel *ioc, const struct iovec *iov, > + size_t niov, off_t offset, Error **errp); > + > /** > * qio_channel_pread > * @ioc: the channel object > diff --git a/io/channel.c b/io/channel.c > index a1f12f8e90..2f1745d052 100644 > --- a/io/channel.c > +++ b/io/channel.c > @@ -472,6 +472,69 @@ ssize_t qio_channel_pwritev(QIOChannel *ioc, const struct iovec *iov, > return klass->io_pwritev(ioc, iov, niov, offset, errp); > } > > +static int qio_channel_preadv_pwritev_contiguous(QIOChannel *ioc, > + const struct iovec *iov, > + size_t niov, off_t offset, > + bool is_write, Error **errp) > +{ > + ssize_t ret = -1; > + int i, slice_idx, slice_num; > + uintptr_t base, next, file_offset; > + size_t len; > + > + slice_idx = 0; > + slice_num = 1; > + > + /* > + * If the iov array doesn't have contiguous elements, we need to > + * split it in slices because we only have one (file) 'offset' for > + * the whole iov. Do this here so callers don't need to break the > + * iov array themselves. > + */ > + for (i = 0; i < niov; i++, slice_num++) { > + base = (uintptr_t) iov[i].iov_base; > + > + if (i != niov - 1) { > + len = iov[i].iov_len; > + next = (uintptr_t) iov[i + 1].iov_base; > + > + if (base + len == next) { > + continue; > + } > + } > + > + /* > + * Use the offset of the first element of the segment that > + * we're sending. > + */ > + file_offset = offset + (uintptr_t) iov[slice_idx].iov_base; > + > + if (is_write) { > + ret = qio_channel_pwritev(ioc, &iov[slice_idx], slice_num, > + file_offset, errp); > + } else { > + ret = qio_channel_preadv(ioc, &iov[slice_idx], slice_num, > + file_offset, errp); > + } iov_base is the address of a pointer in RAM, so could be potentially any 64-bit value. We're assigning file_offset to this pointer address with an user supplied offset, and then using it as an offset on disk. First this could result in 64-bit overflow when 'offset' is added to 'iov_base', and second this could result in a file that's 16 Exabytes in size (with holes of course). I don't get how this is supposed to work, or be used ? > + > + if (ret < 0) { > + break; > + } > + > + slice_idx += slice_num; > + slice_num = 0; > + } > + > + return (ret < 0) ? -1 : 0; > +} > + > +int qio_channel_pwritev_all(QIOChannel *ioc, const struct iovec *iov, > + size_t niov, off_t offset, Error **errp) > +{ > + return qio_channel_preadv_pwritev_contiguous(ioc, iov, niov, > + offset, true, errp); > +} > + > ssize_t qio_channel_pwrite(QIOChannel *ioc, char *buf, size_t buflen, > off_t offset, Error **errp) > { > @@ -501,6 +564,13 @@ ssize_t qio_channel_preadv(QIOChannel *ioc, const struct iovec *iov, > return klass->io_preadv(ioc, iov, niov, offset, errp); > } > > +int qio_channel_preadv_all(QIOChannel *ioc, const struct iovec *iov, > + size_t niov, off_t offset, Error **errp) > +{ > + return qio_channel_preadv_pwritev_contiguous(ioc, iov, niov, > + offset, false, errp); > +} > + > ssize_t qio_channel_pread(QIOChannel *ioc, char *buf, size_t buflen, > off_t offset, Error **errp) > { > -- > 2.35.3 > With 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 :|