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>

1 files changed, 5 insertions, 0 deletions

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;
 }