From patchwork Fri Jul 15 21:32:22 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Schoenebeck X-Patchwork-Id: 12919919 X-Patchwork-Delegate: kuba@kernel.org 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C9E2C43334 for ; Fri, 15 Jul 2022 23:55:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229875AbiGOXze (ORCPT ); Fri, 15 Jul 2022 19:55:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43312 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229586AbiGOXzd (ORCPT ); Fri, 15 Jul 2022 19:55:33 -0400 X-Greylist: delayed 1774 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Fri, 15 Jul 2022 16:55:32 PDT Received: from lizzy.crudebyte.com (lizzy.crudebyte.com [91.194.90.13]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5E4E9904DA for ; Fri, 15 Jul 2022 16:55:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=lizzy; h=Cc:To:Subject:Date:From:References:In-Reply-To: Message-Id:Content-Type:Content-Transfer-Encoding:MIME-Version:Content-ID: Content-Description; bh=03PxLEg7NiaMvhSBPzBFP/XCwo9SFsyuKqJNcoKWY/4=; b=FNoOh ADE4Hg8xvSWs3nC3arwY3n/D4KpC24+zbudVWzCQzQ9Jt44t0D4LfPFv3WNSlveHgFc6/KI89jp4e LC0pEv1M5mVVRvKv+N7xBo9IjLpOl+pyG+ci+ZFb00tI3deorUKHOt6ymu9Zazq4QzWQsBXP3PhGF 2FTl5gNBAbd+9kOPgN6LEW+UHH9eTFypF8WmTbSoX4MxMbEAU7uZO4++cR3Fb04edNhHoWl3J/WaW qzP1rvKlrtZ2sASOR7SA6QFTOU6CcyuZMfLSKmYNzTLM2CprP6GhQJR9/AXSBVavTNCZgOZ7RWKrJ xLhnwIfB3xkgI3w00xTLP83GSiuGw==; Message-Id: In-Reply-To: References: From: Christian Schoenebeck Date: Fri, 15 Jul 2022 23:32:22 +0200 Subject: [PATCH v6 05/11] 9p/trans_virtio: support larger msize values To: v9fs-developer@lists.sourceforge.net Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Dominique Martinet , Eric Van Hensbergen , Latchesar Ionkov , Nikolay Kichukov Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org The virtio transport supports by default a 9p 'msize' of up to approximately 500 kB. This patch adds support for larger 'msize' values by resizing the amount of scatter/gather lists if required. To be more precise, for the moment this patch increases the 'msize' limit for the virtio transport to slightly below 4 MB, virtio transport actually supports much more (tested successfully with an experimental QEMU version and some dirty 9p Linux client hacks up to msize=128MB), but client still uses linear buffers, which in turn are limited to KMALLOC_MAX_SIZE (4M). Signed-off-by: Christian Schoenebeck --- I am not sure if it is safe the way SG lists are resized here. I "think" Dominique said before there should be no concurrency here, but probably deserves a revisit. net/9p/trans_virtio.c | 79 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+) diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c index 5ac533f83322..921caa022570 100644 --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.c @@ -36,6 +36,16 @@ #include #include "trans_common.h" +/* + * Maximum amount of virtio descriptors allowed per virtio round-trip + * message. + * + * This effectively limits msize to (slightly below) 4M, virtio transport + * actually supports much more, but client still uses linear buffers, which + * in turn are limited to KMALLOC_MAX_SIZE (4M). + */ +#define VIRTIO_MAX_DESCRIPTORS 1024 + /** * struct virtqueue_sg - (chained) scatter gather lists for virtqueue data * transmission @@ -203,6 +213,31 @@ static struct virtqueue_sg *vq_sg_alloc(unsigned int nsgl) return vq_sg; } +/** + * vq_sg_resize - resize passed virtqueue scatter/gather lists to the passed + * amount of lists + * @_vq_sg: scatter/gather lists to be resized + * @nsgl: new amount of scatter/gather lists + */ +static int vq_sg_resize(struct virtqueue_sg **_vq_sg, unsigned int nsgl) +{ + struct virtqueue_sg *vq_sg; + + BUG_ON(!_vq_sg || !nsgl); + vq_sg = *_vq_sg; + if (vq_sg->nsgl == nsgl) + return 0; + + /* lazy resize implementation for now */ + vq_sg = vq_sg_alloc(nsgl); + if (!vq_sg) + return -ENOMEM; + + kfree(*_vq_sg); + *_vq_sg = vq_sg; + return 0; +} + /** * p9_virtio_close - reclaim resources of a channel * @client: client instance @@ -774,6 +809,10 @@ p9_virtio_create(struct p9_client *client, const char *devname, char *args) struct virtio_chan *chan; int ret = -ENOENT; int found = 0; +#if !defined(CONFIG_ARCH_NO_SG_CHAIN) + size_t npages; + size_t nsgl; +#endif if (devname == NULL) return -EINVAL; @@ -796,6 +835,46 @@ p9_virtio_create(struct p9_client *client, const char *devname, char *args) return ret; } + /* + * if user supplied an 'msize' option that's larger than what this + * transport supports by default, then try to allocate more sg lists + */ + if (client->msize > client->trans_maxsize) { +#ifdef CONFIG_ARCH_NO_SG_CHAIN + pr_info("limiting 'msize' to %d because architecture does not " + "support chained scatter gather lists\n", + client->trans_maxsize); +#else + npages = DIV_ROUND_UP(client->msize, PAGE_SIZE); + if (npages > VIRTIO_MAX_DESCRIPTORS) + npages = VIRTIO_MAX_DESCRIPTORS; + if (npages > chan->p9_max_pages) { + npages = chan->p9_max_pages; + pr_info("limiting 'msize' as it would exceed the max. " + "of %lu pages allowed on this system\n", + chan->p9_max_pages); + } + nsgl = DIV_ROUND_UP(npages, SG_USER_PAGES_PER_LIST); + if (nsgl > chan->vq_sg->nsgl) { + /* + * if resize fails, no big deal, then just continue with + * whatever we got + */ + if (!vq_sg_resize(&chan->vq_sg, nsgl)) { + /* + * decrement 2 pages as both 9p request and 9p reply have + * to fit into the virtio round-trip message + */ + client->trans_maxsize = + PAGE_SIZE * + clamp_t(int, + (nsgl * SG_USER_PAGES_PER_LIST) - 2, + 0, VIRTIO_MAX_DESCRIPTORS - 2); + } + } +#endif /* CONFIG_ARCH_NO_SG_CHAIN */ + } + client->trans = (void *)chan; client->status = Connected; chan->client = client;