linux: use copy_file_range for uv_fs_copyfile when possible

.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+    "files.associations": {
+        "syscall.h": "c"
+    }
+}

src/unix/fs.c

@@ -59,6 +59,11 @@
 # include <sys/sendfile.h>
 #endif
 
+#if defined(__linux__)
+# include <sys/syscall.h>
+# include <sys/types.h>
+#endif
+
 #if defined(__APPLE__)
 # include <sys/sysctl.h>
 #elif defined(__linux__) && !defined(FICLONE)
@@ -736,6 +741,15 @@ static ssize_t uv__fs_sendfile_emul(uv_fs_t* req) {
   return nsent;
 }
 
+#ifdef __NR_copy_file_range
+static loff_t
+uv__fs_copy_file_range(int fd_in, loff_t *off_in, int fd_out,
+                loff_t *off_out, size_t len, unsigned int flags)
+{
+  return syscall(__NR_copy_file_range, fd_in, off_in,
+                 fd_out, off_out, len, flags);
+}
+#endif
 
 static ssize_t uv__fs_sendfile(uv_fs_t* req) {
   int in_fd;
@@ -750,8 +764,25 @@ static ssize_t uv__fs_sendfile(uv_fs_t* req) {
     ssize_t r;
 
     off = req->off;
+
+#ifdef __NR_copy_file_range
+    static int copy_file_range_support = 1;
+
+    if (copy_file_range_support) {
+      r = uv__fs_copy_file_range(in_fd, NULL, out_fd, &off, req->bufsml[0].len, 0);
+
+      if (r == -1 && errno == ENOSYS) {
+        errno = 0;
+        copy_file_range_support = 0;
+      } else {
+        goto ok;
+      }
+    }
+#endif
+
     r = sendfile(out_fd, in_fd, &off, req->bufsml[0].len);
 
+ok:
     /* sendfile() on SunOS returns EINVAL if the target fd is not a socket but
      * it still writes out data. Fortunately, we can detect it by checking if
      * the offset has been updated.