From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Date: Mon, 27 Jan 2020 19:01:06 +0000
Subject: [PATCH] virtiofsd: Fast path for virtio read
Readv the data straight into the guests buffer.
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
With fix by:
Signed-off-by: Eryu Guan <eguan@linux.alibaba.com>
Reviewed-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
(cherry picked from commit eb49d187ef5134483a34c970bbfece28aaa686a7)
---
tools/virtiofsd/fuse_lowlevel.c | 5 +
tools/virtiofsd/fuse_virtio.c | 162 ++++++++++++++++++++++++++++++++
tools/virtiofsd/fuse_virtio.h | 4 +
3 files changed, 171 insertions(+)
diff --git a/tools/virtiofsd/fuse_lowlevel.c b/tools/virtiofsd/fuse_lowlevel.c
index 380d93bd01..4f4684d942 100644
--- a/tools/virtiofsd/fuse_lowlevel.c
+++ b/tools/virtiofsd/fuse_lowlevel.c
@@ -475,6 +475,11 @@ static int fuse_send_data_iov_fallback(struct fuse_session *se,
return fuse_send_msg(se, ch, iov, iov_count);
}
+ if (fuse_lowlevel_is_virtio(se) && buf->count == 1 &&
+ buf->buf[0].flags == (FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK)) {
+ return virtio_send_data_iov(se, ch, iov, iov_count, buf, len);
+ }
+
abort(); /* Will have taken vhost path */
return 0;
}
diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c
index f1adeb6345..7e2711b504 100644
--- a/tools/virtiofsd/fuse_virtio.c
+++ b/tools/virtiofsd/fuse_virtio.c
@@ -230,6 +230,168 @@ err:
return ret;
}
+/*
+ * Callback from fuse_send_data_iov_* when it's virtio and the buffer
+ * is a single FD with FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK
+ * We need send the iov and then the buffer.
+ * Return 0 on success
+ */
+int virtio_send_data_iov(struct fuse_session *se, struct fuse_chan *ch,
+ struct iovec *iov, int count, struct fuse_bufvec *buf,
+ size_t len)
+{
+ int ret = 0;
+ VuVirtqElement *elem;
+ VuVirtq *q;
+
+ assert(count >= 1);
+ assert(iov[0].iov_len >= sizeof(struct fuse_out_header));
+
+ struct fuse_out_header *out = iov[0].iov_base;
+ /* TODO: Endianness! */
+
+ size_t iov_len = iov_size(iov, count);
+ size_t tosend_len = iov_len + len;
+
+ out->len = tosend_len;
+
+ fuse_log(FUSE_LOG_DEBUG, "%s: count=%d len=%zd iov_len=%zd\n", __func__,
+ count, len, iov_len);
+
+ /* unique == 0 is notification which we don't support */
+ assert(out->unique);
+
+ /* For virtio we always have ch */
+ assert(ch);
+ assert(!ch->qi->reply_sent);
+ elem = ch->qi->qe;
+ q = &ch->qi->virtio_dev->dev.vq[ch->qi->qidx];
+
+ /* The 'in' part of the elem is to qemu */
+ unsigned int in_num = elem->in_num;
+ struct iovec *in_sg = elem->in_sg;
+ size_t in_len = iov_size(in_sg, in_num);
+ fuse_log(FUSE_LOG_DEBUG, "%s: elem %d: with %d in desc of length %zd\n",
+ __func__, elem->index, in_num, in_len);
+
+ /*
+ * The elem should have room for a 'fuse_out_header' (out from fuse)
+ * plus the data based on the len in the header.
+ */
+ if (in_len < sizeof(struct fuse_out_header)) {
+ fuse_log(FUSE_LOG_ERR, "%s: elem %d too short for out_header\n",
+ __func__, elem->index);
+ ret = E2BIG;
+ goto err;
+ }
+ if (in_len < tosend_len) {
+ fuse_log(FUSE_LOG_ERR, "%s: elem %d too small for data len %zd\n",
+ __func__, elem->index, tosend_len);
+ ret = E2BIG;
+ goto err;
+ }
+
+ /* TODO: Limit to 'len' */
+
+ /* First copy the header data from iov->in_sg */
+ copy_iov(iov, count, in_sg, in_num, iov_len);
+
+ /*
+ * Build a copy of the the in_sg iov so we can skip bits in it,
+ * including changing the offsets
+ */
+ struct iovec *in_sg_cpy = calloc(sizeof(struct iovec), in_num);
+ assert(in_sg_cpy);
+ memcpy(in_sg_cpy, in_sg, sizeof(struct iovec) * in_num);
+ /* These get updated as we skip */
+ struct iovec *in_sg_ptr = in_sg_cpy;
+ int in_sg_cpy_count = in_num;
+
+ /* skip over parts of in_sg that contained the header iov */
+ size_t skip_size = iov_len;
+
+ size_t in_sg_left = 0;
+ do {
+ while (skip_size != 0 && in_sg_cpy_count) {
+ if (skip_size >= in_sg_ptr[0].iov_len) {
+ skip_size -= in_sg_ptr[0].iov_len;
+ in_sg_ptr++;
+ in_sg_cpy_count--;
+ } else {
+ in_sg_ptr[0].iov_len -= skip_size;
+ in_sg_ptr[0].iov_base += skip_size;
+ break;
+ }
+ }
+
+ int i;
+ for (i = 0, in_sg_left = 0; i < in_sg_cpy_count; i++) {
+ in_sg_left += in_sg_ptr[i].iov_len;
+ }
+ fuse_log(FUSE_LOG_DEBUG,
+ "%s: after skip skip_size=%zd in_sg_cpy_count=%d "
+ "in_sg_left=%zd\n",
+ __func__, skip_size, in_sg_cpy_count, in_sg_left);
+ ret = preadv(buf->buf[0].fd, in_sg_ptr, in_sg_cpy_count,
+ buf->buf[0].pos);
+
+ if (ret == -1) {
+ ret = errno;
+ fuse_log(FUSE_LOG_DEBUG, "%s: preadv failed (%m) len=%zd\n",
+ __func__, len);
+ free(in_sg_cpy);
+ goto err;
+ }
+ fuse_log(FUSE_LOG_DEBUG, "%s: preadv ret=%d len=%zd\n", __func__,
+ ret, len);
+ if (ret < len && ret) {
+ fuse_log(FUSE_LOG_DEBUG, "%s: ret < len\n", __func__);
+ /* Skip over this much next time around */
+ skip_size = ret;
+ buf->buf[0].pos += ret;
+ len -= ret;
+
+ /* Lets do another read */
+ continue;
+ }
+ if (!ret) {
+ /* EOF case? */
+ fuse_log(FUSE_LOG_DEBUG, "%s: !ret in_sg_left=%zd\n", __func__,
+ in_sg_left);
+ break;
+ }
+ if (ret != len) {
+ fuse_log(FUSE_LOG_DEBUG, "%s: ret!=len\n", __func__);
+ ret = EIO;
+ free(in_sg_cpy);
+ goto err;
+ }
+ in_sg_left -= ret;
+ len -= ret;
+ } while (in_sg_left);
+ free(in_sg_cpy);
+
+ /* Need to fix out->len on EOF */
+ if (len) {
+ struct fuse_out_header *out_sg = in_sg[0].iov_base;
+
+ tosend_len -= len;
+ out_sg->len = tosend_len;
+ }
+
+ ret = 0;
+
+ vu_queue_push(&se->virtio_dev->dev, q, elem, tosend_len);
+ vu_queue_notify(&se->virtio_dev->dev, q);
+
+err:
+ if (ret == 0) {
+ ch->qi->reply_sent = true;
+ }
+
+ return ret;
+}
+
/* Thread function for individual queues, created when a queue is 'started' */
static void *fv_queue_thread(void *opaque)
{
diff --git a/tools/virtiofsd/fuse_virtio.h b/tools/virtiofsd/fuse_virtio.h
index 135a14875a..cc676b9193 100644
--- a/tools/virtiofsd/fuse_virtio.h
+++ b/tools/virtiofsd/fuse_virtio.h
@@ -26,4 +26,8 @@ int virtio_loop(struct fuse_session *se);
int virtio_send_msg(struct fuse_session *se, struct fuse_chan *ch,
struct iovec *iov, int count);
+int virtio_send_data_iov(struct fuse_session *se, struct fuse_chan *ch,
+ struct iovec *iov, int count,
+ struct fuse_bufvec *buf, size_t len);
+
#endif