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From: Christian Schoenebeck <linux_oss@crudebyte.com>
To: v9fs-developer@lists.sourceforge.net
Cc: netdev@vger.kernel.org,
	Dominique Martinet <asmadeus@codewreck.org>,
	Eric Van Hensbergen <ericvh@gmail.com>,
	Latchesar Ionkov <lucho@ionkov.net>, Greg Kurz <groug@kaod.org>,
	Vivek Goyal <vgoyal@redhat.com>
Subject: [PATCH v3 6/7] 9p/trans_virtio: support larger msize values
Date: Wed, 22 Sep 2021 18:00:33 +0200	[thread overview]
Message-ID: <8119d4d93a39758075bb83730dcb571f5d071af6.1632327421.git.linux_oss@crudebyte.com> (raw)
In-Reply-To: <cover.1632327421.git.linux_oss@crudebyte.com>

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.

Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com>
---
 net/9p/trans_virtio.c | 61 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index e478a34326f1..147ebf647a95 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -203,6 +203,31 @@ 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 +799,10 @@ 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 +825,38 @@ 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 > 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 default msize instead
+			 */
+			if (!vq_sg_resize(&chan->vq_sg, nsgl)) {
+				client->trans_maxsize =
+					PAGE_SIZE *
+					((nsgl * SG_USER_PAGES_PER_LIST) - 3);
+			}
+		}
+#endif /* CONFIG_ARCH_NO_SG_CHAIN */
+	}
+
 	client->trans = (void *)chan;
 	client->status = Connected;
 	chan->client = client;
-- 
2.20.1


  parent reply	other threads:[~2021-09-22 18:00 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-22 16:00 [PATCH v3 0/7] net/9p: remove msize limit in virtio transport Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 1/7] net/9p: show error message if user 'msize' cannot be satisfied Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 2/7] 9p/trans_virtio: separate allocation of scatter gather list Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 3/7] 9p/trans_virtio: turn amount of sg lists into runtime info Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 4/7] 9p/trans_virtio: introduce struct virtqueue_sg Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 5/7] net/9p: add trans_maxsize to struct p9_client Christian Schoenebeck
2021-09-22 16:00 ` Christian Schoenebeck [this message]
2021-11-20 11:20   ` [PATCH v3 6/7] 9p/trans_virtio: support larger msize values Nikolay Kichukov
2021-11-20 11:45     ` Dominique Martinet
2021-11-20 14:46       ` Christian Schoenebeck
2021-11-20 21:28         ` Nikolay Kichukov
2021-11-20 23:02         ` Dominique Martinet
2021-11-21 16:57           ` Christian Schoenebeck
2021-11-21 22:12             ` Dominique Martinet
2021-11-22 13:32               ` Christian Schoenebeck
2021-11-22 22:35                 ` Dominique Martinet
2021-11-24 12:22                   ` Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 7/7] 9p/trans_virtio: resize sg lists to whatever is possible Christian Schoenebeck

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