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virtiofsd: Fast path for virtio read

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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>
This commit is contained in:
Dr. David Alan Gilbert 2018-08-15 20:26:05 +01:00
parent 81bfc42dcf
commit eb49d187ef
3 changed files with 171 additions and 0 deletions
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5
tools/virtiofsd/fuse_lowlevel.c
View File

@ -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;
}

162
tools/virtiofsd/fuse_virtio.c
View File

@ -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)
{

4
tools/virtiofsd/fuse_virtio.h
View File

@ -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