1 files changed, 18 insertions, 2 deletions
diff --git a/tools/virtiofsd/buffer.c b/tools/virtiofsd/buffer.c
index 37befebac2..27c1377f22 100644
--- a/tools/virtiofsd/buffer.c
+++ b/tools/virtiofsd/buffer.c
@@ -34,7 +34,6 @@ size_t fuse_buf_size(const struct fuse_bufvec *bufv)
     return size;
 }
 
-__attribute__((unused))
 static ssize_t fuse_buf_writev(struct fuse_buf *out_buf,
                                struct fuse_bufvec *in_buf)
 {
@@ -262,12 +261,29 @@ static int fuse_bufvec_advance(struct fuse_bufvec *bufv, size_t len)
 
 ssize_t fuse_buf_copy(struct fuse_bufvec *dstv, struct fuse_bufvec *srcv)
 {
-    size_t copied = 0;
+    size_t copied = 0, i;
 
     if (dstv == srcv) {
         return fuse_buf_size(dstv);
     }
 
+    /*
+     * use writev to improve bandwidth when all the
+     * src buffers already mapped by the daemon
+     * process
+     */
+    for (i = 0; i < srcv->count; i++) {
+        if (srcv->buf[i].flags & FUSE_BUF_IS_FD) {
+            break;
+        }
+    }
+    if ((i == srcv->count) && (dstv->count == 1) &&
+        (dstv->idx == 0) &&
+        (dstv->buf[0].flags & FUSE_BUF_IS_FD)) {
+        dstv->buf[0].pos += dstv->off;
+        return fuse_buf_writev(&dstv->buf[0], srcv);
+    }
+
     for (;;) {
         const struct fuse_buf *src = fuse_bufvec_current(srcv);
         const struct fuse_buf *dst = fuse_bufvec_current(dstv);