From patchwork Thu Dec 30 13:23:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Schoenebeck X-Patchwork-Id: 12701455 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 4B13AC433F5 for ; Thu, 30 Dec 2021 14:12:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239849AbhL3OMk (ORCPT ); Thu, 30 Dec 2021 09:12:40 -0500 Received: from lizzy.crudebyte.com ([91.194.90.13]:34649 "EHLO lizzy.crudebyte.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233197AbhL3OMk (ORCPT ); Thu, 30 Dec 2021 09:12:40 -0500 X-Greylist: delayed 2520 seconds by postgrey-1.27 at vger.kernel.org; Thu, 30 Dec 2021 09:12:39 EST 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=WP3n7tpB+D025yF74slHQQEWSBQcJ+0mlSqy58dljRg=; b=mj+An VdLfCm7I8hkOEG8OaVBcxxclOtqULbLWn2iSvVIeFLqAJzH+K4L6Vcii703ZyKiHJgOu7cDxRq9VS 5h4PIhoQq8+oiGBYIIhZnEpgQ9r4o5mUHIPXN8jSweWxz9eGuLB0CGeDnNdg5843g7LHn5wcD7/hf zEF2IunkwlavqyqpY0It3N83g2NBRjMoFBVolaiMa61Qw7g83J7tp3yPlcuDpqIE56Gh01Vf74QXh KUEJYBPL6F6FARJB5lJfzzwuGTmoVQCrHgomJSD1DeAle5yL4JTCxOUPvpQYA0OUD+S1ArNLPW/1V 1vEDOpeXWqoXGJOmvyxMVqNq5uiuw==; Message-Id: <103e92cc446c58d459c034973481d2f763a7006e.1640870037.git.linux_oss@crudebyte.com> In-Reply-To: References: From: Christian Schoenebeck Date: Thu, 30 Dec 2021 14:23:18 +0100 Subject: [PATCH v4 04/12] 9p/trans_virtio: introduce struct virtqueue_sg To: v9fs-developer@lists.sourceforge.net Cc: netdev@vger.kernel.org, Dominique Martinet , Eric Van Hensbergen , Latchesar Ionkov , Greg Kurz , Vivek Goyal , Nikolay Kichukov Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org The amount of elements in a scatter/gather list is limited to approximately 128 elements. To allow going beyond that limit with subsequent patches, pave the way by turning the one- dimensional sg list array into a two-dimensional array, i.e: sg[128] becomes sgl[nsgl][SG_MAX_SINGLE_ALLOC] As the value of 'nsgl' is exactly (still) 1 in this commit and the compile-time (compiler and architecture dependent) value of 'SG_MAX_SINGLE_ALLOC' equals approximately the previous hard coded 128 elements, this commit is therefore more of a preparatory refactoring then actual behaviour change. A custom struct virtqueue_sg is defined instead of using shared API struct sg_table, because the latter would not allow to resize the table after allocation. sg_append_table API OTOH would not fit either, because it requires a list of pages beforehand upon allocation. And both APIs only support all-or-nothing allocation. Signed-off-by: Christian Schoenebeck --- net/9p/trans_virtio.c | 193 ++++++++++++++++++++++++++++++++---------- 1 file changed, 147 insertions(+), 46 deletions(-) diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c index d063c69b85b7..656562a66f06 100644 --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.c @@ -36,7 +36,31 @@ #include #include "trans_common.h" -#define VIRTQUEUE_DEFAULT_NUM 128 +/** + * struct virtqueue_sg - (chained) scatter gather lists for virtqueue data + * transmission + * @nsgl: amount of elements (in first dimension) of array field @sgl + * @sgl: two-dimensional array, i.e. sgl[nsgl][SG_MAX_SINGLE_ALLOC] + */ +struct virtqueue_sg { + unsigned int nsgl; + struct scatterlist *sgl[]; +}; + +/* + * Default value for field nsgl in struct virtqueue_sg, which defines the + * initial virtio data transmission capacity when this virtio transport is + * probed. + */ +#define VIRTQUEUE_SG_NSGL_DEFAULT 1 + +/* maximum value for field nsgl in struct virtqueue_sg */ +#define VIRTQUEUE_SG_NSGL_MAX \ + ((PAGE_SIZE - sizeof(struct virtqueue_sg)) / \ + sizeof(struct scatterlist *)) \ + +/* last entry per sg list is used for chaining (pointer to next list) */ +#define SG_USER_PAGES_PER_LIST (SG_MAX_SINGLE_ALLOC - 1) /* a single mutex to manage channel initialization and attachment */ static DEFINE_MUTEX(virtio_9p_lock); @@ -53,8 +77,7 @@ static atomic_t vp_pinned = ATOMIC_INIT(0); * @ring_bufs_avail: flag to indicate there is some available in the ring buf * @vc_wq: wait queue for waiting for thing to be added to ring buf * @p9_max_pages: maximum number of pinned pages - * @sg: scatter gather list which is used to pack a request (protected?) - * @sg_n: amount of elements in sg array + * @vq_sg: table of scatter gather lists, which are used to pack a request * @chan_list: linked list of channels * * We keep all per-channel information in a structure. @@ -77,9 +100,7 @@ struct virtio_chan { * will be placing it in each channel. */ unsigned long p9_max_pages; - /* Scatterlist: can be too big for stack. */ - struct scatterlist *sg; - size_t sg_n; + struct virtqueue_sg *vq_sg; /** * @tag: name to identify a mount null terminated */ @@ -96,6 +117,92 @@ static unsigned int rest_of_page(void *data) return PAGE_SIZE - offset_in_page(data); } +/** + * vq_sg_page - returns user page for given page index + * @vq_sg: scatter gather lists used by this transport + * @page: user page index across all scatter gather lists + */ +static struct scatterlist *vq_sg_page(struct virtqueue_sg *vq_sg, size_t page) +{ + unsigned int node = page / SG_USER_PAGES_PER_LIST; + unsigned int leaf = page % SG_USER_PAGES_PER_LIST; + BUG_ON(node >= VIRTQUEUE_SG_NSGL_MAX); + return &vq_sg->sgl[node][leaf]; +} + +/** + * vq_sg_npages - returns total number of individual user pages in passed + * scatter gather lists + * @vq_sg: scatter gather lists to be counted + */ +static size_t vq_sg_npages(struct virtqueue_sg *vq_sg) +{ + return vq_sg->nsgl * SG_USER_PAGES_PER_LIST; +} + +/** + * vq_sg_free - free all memory previously allocated for @vq_sg + * @vq_sg: scatter gather lists to be freed + */ +static void vq_sg_free(struct virtqueue_sg *vq_sg) +{ + unsigned int i; + + if (!vq_sg) + return; + + for (i = 0; i < vq_sg->nsgl; ++i) { + kfree(vq_sg->sgl[i]); + } + kfree(vq_sg); +} + +/** + * vq_sg_alloc - allocates and returns @nsgl scatter gather lists + * @nsgl: amount of scatter gather lists to be allocated + * If @nsgl is larger than one then chained lists are used if supported by + * architecture. + */ +static struct virtqueue_sg *vq_sg_alloc(unsigned int nsgl) +{ + struct virtqueue_sg *vq_sg; + unsigned int i; + + BUG_ON(!nsgl || nsgl > VIRTQUEUE_SG_NSGL_MAX); +#ifdef CONFIG_ARCH_NO_SG_CHAIN + if (WARN_ON_ONCE(nsgl > 1)) + return NULL; +#endif + + vq_sg = kzalloc(sizeof(struct virtqueue_sg) + + nsgl * sizeof(struct scatterlist *), + GFP_KERNEL); + + if (!vq_sg) + return NULL; + + vq_sg->nsgl = nsgl; + + for (i = 0; i < nsgl; ++i) { + vq_sg->sgl[i] = kmalloc_array( + SG_MAX_SINGLE_ALLOC, sizeof(struct scatterlist), + GFP_KERNEL + ); + if (!vq_sg->sgl[i]) { + vq_sg_free(vq_sg); + return NULL; + } + sg_init_table(vq_sg->sgl[i], SG_MAX_SINGLE_ALLOC); + if (i) { + /* chain the lists */ + sg_chain(vq_sg->sgl[i - 1], SG_MAX_SINGLE_ALLOC, + vq_sg->sgl[i]); + } + } + sg_mark_end(&vq_sg->sgl[nsgl - 1][SG_MAX_SINGLE_ALLOC - 1]); + return vq_sg; +} + /** * p9_virtio_close - reclaim resources of a channel * @client: client instance @@ -158,9 +265,8 @@ static void req_done(struct virtqueue *vq) /** * pack_sg_list - pack a scatter gather list from a linear buffer - * @sg: scatter/gather list to pack into + * @vq_sg: scatter/gather lists to pack into * @start: which segment of the sg_list to start at - * @limit: maximum segment to pack data to * @data: data to pack into scatter/gather list * @count: amount of data to pack into the scatter/gather list * @@ -170,11 +276,12 @@ static void req_done(struct virtqueue *vq) * */ -static int pack_sg_list(struct scatterlist *sg, int start, - int limit, char *data, int count) +static int pack_sg_list(struct virtqueue_sg *vq_sg, int start, + char *data, int count) { int s; int index = start; + size_t limit = vq_sg_npages(vq_sg); while (count) { s = rest_of_page(data); @@ -182,13 +289,13 @@ static int pack_sg_list(struct scatterlist *sg, int start, s = count; BUG_ON(index >= limit); /* Make sure we don't terminate early. */ - sg_unmark_end(&sg[index]); - sg_set_buf(&sg[index++], data, s); + sg_unmark_end(vq_sg_page(vq_sg, index)); + sg_set_buf(vq_sg_page(vq_sg, index++), data, s); count -= s; data += s; } if (index-start) - sg_mark_end(&sg[index - 1]); + sg_mark_end(vq_sg_page(vq_sg, index - 1)); return index-start; } @@ -208,21 +315,21 @@ static int p9_virtio_cancelled(struct p9_client *client, struct p9_req_t *req) /** * pack_sg_list_p - Just like pack_sg_list. Instead of taking a buffer, * this takes a list of pages. - * @sg: scatter/gather list to pack into + * @vq_sg: scatter/gather lists to pack into * @start: which segment of the sg_list to start at - * @limit: maximum number of pages in sg list. * @pdata: a list of pages to add into sg. * @nr_pages: number of pages to pack into the scatter/gather list * @offs: amount of data in the beginning of first page _not_ to pack * @count: amount of data to pack into the scatter/gather list */ static int -pack_sg_list_p(struct scatterlist *sg, int start, int limit, +pack_sg_list_p(struct virtqueue_sg *vq_sg, int start, struct page **pdata, int nr_pages, size_t offs, int count) { int i = 0, s; int data_off = offs; int index = start; + size_t limit = vq_sg_npages(vq_sg); BUG_ON(nr_pages > (limit - start)); /* @@ -235,15 +342,16 @@ pack_sg_list_p(struct scatterlist *sg, int start, int limit, s = count; BUG_ON(index >= limit); /* Make sure we don't terminate early. */ - sg_unmark_end(&sg[index]); - sg_set_page(&sg[index++], pdata[i++], s, data_off); + sg_unmark_end(vq_sg_page(vq_sg, index)); + sg_set_page(vq_sg_page(vq_sg, index++), pdata[i++], s, + data_off); data_off = 0; count -= s; nr_pages--; } if (index-start) - sg_mark_end(&sg[index - 1]); + sg_mark_end(vq_sg_page(vq_sg, index - 1)); return index - start; } @@ -271,15 +379,13 @@ p9_virtio_request(struct p9_client *client, struct p9_req_t *req) out_sgs = in_sgs = 0; /* Handle out VirtIO ring buffers */ - out = pack_sg_list(chan->sg, 0, - chan->sg_n, req->tc.sdata, req->tc.size); + out = pack_sg_list(chan->vq_sg, 0, req->tc.sdata, req->tc.size); if (out) - sgs[out_sgs++] = chan->sg; + sgs[out_sgs++] = vq_sg_page(chan->vq_sg, 0); - in = pack_sg_list(chan->sg, out, - chan->sg_n, req->rc.sdata, req->rc.capacity); + in = pack_sg_list(chan->vq_sg, out, req->rc.sdata, req->rc.capacity); if (in) - sgs[out_sgs + in_sgs++] = chan->sg + out; + sgs[out_sgs + in_sgs++] = vq_sg_page(chan->vq_sg, out); err = virtqueue_add_sgs(chan->vq, sgs, out_sgs, in_sgs, req, GFP_ATOMIC); @@ -448,16 +554,15 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req, out_sgs = in_sgs = 0; /* out data */ - out = pack_sg_list(chan->sg, 0, - chan->sg_n, req->tc.sdata, req->tc.size); + out = pack_sg_list(chan->vq_sg, 0, req->tc.sdata, req->tc.size); if (out) - sgs[out_sgs++] = chan->sg; + sgs[out_sgs++] = vq_sg_page(chan->vq_sg, 0); if (out_pages) { - sgs[out_sgs++] = chan->sg + out; - out += pack_sg_list_p(chan->sg, out, chan->sg_n, - out_pages, out_nr_pages, offs, outlen); + sgs[out_sgs++] = vq_sg_page(chan->vq_sg, out); + out += pack_sg_list_p(chan->vq_sg, out, out_pages, + out_nr_pages, offs, outlen); } /* @@ -467,15 +572,14 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req, * Arrange in such a way that server places header in the * allocated memory and payload onto the user buffer. */ - in = pack_sg_list(chan->sg, out, - chan->sg_n, req->rc.sdata, in_hdr_len); + in = pack_sg_list(chan->vq_sg, out, req->rc.sdata, in_hdr_len); if (in) - sgs[out_sgs + in_sgs++] = chan->sg + out; + sgs[out_sgs + in_sgs++] = vq_sg_page(chan->vq_sg, out); if (in_pages) { - sgs[out_sgs + in_sgs++] = chan->sg + out + in; - in += pack_sg_list_p(chan->sg, out + in, chan->sg_n, - in_pages, in_nr_pages, offs, inlen); + sgs[out_sgs + in_sgs++] = vq_sg_page(chan->vq_sg, out + in); + in += pack_sg_list_p(chan->vq_sg, out + in, in_pages, + in_nr_pages, offs, inlen); } BUG_ON(out_sgs + in_sgs > ARRAY_SIZE(sgs)); @@ -576,14 +680,12 @@ static int p9_virtio_probe(struct virtio_device *vdev) goto fail; } - chan->sg = kmalloc_array(VIRTQUEUE_DEFAULT_NUM, - sizeof(struct scatterlist), GFP_KERNEL); - if (!chan->sg) { + chan->vq_sg = vq_sg_alloc(VIRTQUEUE_SG_NSGL_DEFAULT); + if (!chan->vq_sg) { pr_err("Failed to allocate virtio 9P channel\n"); err = -ENOMEM; goto out_free_chan_shallow; } - chan->sg_n = VIRTQUEUE_DEFAULT_NUM; chan->vdev = vdev; @@ -596,8 +698,6 @@ static int p9_virtio_probe(struct virtio_device *vdev) chan->vq->vdev->priv = chan; spin_lock_init(&chan->lock); - sg_init_table(chan->sg, chan->sg_n); - chan->inuse = false; if (virtio_has_feature(vdev, VIRTIO_9P_MOUNT_TAG)) { virtio_cread(vdev, struct virtio_9p_config, tag_len, &tag_len); @@ -646,7 +746,7 @@ static int p9_virtio_probe(struct virtio_device *vdev) out_free_vq: vdev->config->del_vqs(vdev); out_free_chan: - kfree(chan->sg); + vq_sg_free(chan->vq_sg); out_free_chan_shallow: kfree(chan); fail: @@ -741,7 +841,7 @@ static void p9_virtio_remove(struct virtio_device *vdev) kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE); kfree(chan->tag); kfree(chan->vc_wq); - kfree(chan->sg); + vq_sg_free(chan->vq_sg); kfree(chan); } @@ -780,7 +880,8 @@ static struct p9_trans_module p9_virtio_trans = { * that are not at page boundary, that can result in an extra * page in zero copy. */ - .maxsize = PAGE_SIZE * (VIRTQUEUE_DEFAULT_NUM - 3), + .maxsize = PAGE_SIZE * + ((VIRTQUEUE_SG_NSGL_DEFAULT * SG_USER_PAGES_PER_LIST) - 3), .def = 1, .owner = THIS_MODULE, };