linux: use copy_file_range for uv_fs_copyfile when possible

Refs: https://github.com/libuv/libuv/issues/925#issuecomment-234696227
PR-URL: https://github.com/libuv/libuv/pull/2352
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Jameson Nash <vtjnash@gmail.com>

src/unix/fs.c

@@ -883,8 +883,27 @@ static ssize_t uv__fs_sendfile(uv_fs_t* req) {
     ssize_t r;
 
     off = req->off;
+
+#ifdef __linux__
+    {
+      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.

src/unix/linux-syscalls.c

@@ -94,6 +94,24 @@
 # endif
 #endif /* __NR_pwritev */
 
+#ifndef __NR_copy_file_range
+# if defined(__x86_64__)
+#  define __NR_copy_file_range 326
+# elif defined(__i386__)
+#  define __NR_copy_file_range 377
+# elif defined(__s390__)
+#  define __NR_copy_file_range 375
+# elif defined(__arm__)
+#  define __NR_copy_file_range (UV_SYSCALL_BASE + 391)
+# elif defined(__aarch64__)
+#  define __NR_copy_file_range 285
+# elif defined(__powerpc__)
+#  define __NR_copy_file_range 379
+# elif defined(__arc__)
+#  define __NR_copy_file_range 285
+# endif
+#endif /* __NR_copy_file_range */
+
 #ifndef __NR_statx
 # if defined(__x86_64__)
 #  define __NR_statx 332
@@ -180,6 +198,28 @@ int uv__dup3(int oldfd, int newfd, int flags) {
 }
 
 
+ssize_t
+uv__fs_copy_file_range(int fd_in,
+                       ssize_t* off_in,
+                       int fd_out,
+                       ssize_t* off_out,
+                       size_t len,
+                       unsigned int flags)
+{
+#ifdef __NR_copy_file_range
+  return syscall(__NR_copy_file_range,
+                 fd_in,
+                 off_in,
+                 fd_out,
+                 off_out,
+                 len,
+                 flags);
+#else
+  return errno = ENOSYS, -1;
+#endif
+}
+
+
 int uv__statx(int dirfd,
               const char* path,
               int flags,

src/unix/linux-syscalls.h

@@ -64,6 +64,13 @@ struct uv__statx {
 ssize_t uv__preadv(int fd, const struct iovec *iov, int iovcnt, int64_t offset);
 ssize_t uv__pwritev(int fd, const struct iovec *iov, int iovcnt, int64_t offset);
 int uv__dup3(int oldfd, int newfd, int flags);
+ssize_t
+uv__fs_copy_file_range(int fd_in,
+                       ssize_t* off_in,
+                       int fd_out,
+                       ssize_t* off_out,
+                       size_t len,
+                       unsigned int flags);
 int uv__statx(int dirfd,
               const char* path,
               int flags,