@@ -36,7 +36,31 @@
#include <linux/virtio_9p.h>
#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,
};
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 <linux_oss@crudebyte.com> --- net/9p/trans_virtio.c | 193 ++++++++++++++++++++++++++++++++---------- 1 file changed, 147 insertions(+), 46 deletions(-)