io.c: fix IO.copy_stream on O_APPEND destination on Linux

Linux copy_file_range(2) fails with EBADF if the destination FD
has O_APPEND set.  Preserve existing (Ruby <= 2.4) behavior by
falling back to alternative copy mechanisms if this is the case
(instead of raising Errno::EBADF).

* io.c (nogvl_copy_file_range): do not raise on O_APPEND dst
* test/ruby/test_io.rb (test_copy_stream_append): new test
  [Feature #13867]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60490 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 20 insertions, 0 deletions

diff --git a/io.c b/io.c
index 50395f1f40..5d68eea318 100644
--- a/io.c
+++ b/io.c
@@ -10789,6 +10789,16 @@ nogvl_copy_file_range(struct copy_stream_struct *stp)
             if (nogvl_copy_stream_wait_write(stp) == -1)
                 return -1;
             goto retry_copy_file_range;
+	  case EBADF:
+	    {
+		int e = errno;
+		int flags = fcntl(stp->dst_fd, F_GETFL);
+
+		if (flags != -1 && flags & O_APPEND) {
+		    return 0;
+		}
+		errno = e;
+	    }
         }
         stp->syserr = "copy_file_range";
         stp->error_no = errno;
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index b5d69d9ba4..7f86b4ebaf 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -366,6 +366,16 @@ class TestIO < Test::Unit::TestCase
     }
   end
 
+  def test_copy_stream_append
+    with_srccontent("foobar") {|src, content|
+      File.open('dst', 'ab') do |dst|
+        ret = IO.copy_stream(src, dst)
+        assert_equal(content.bytesize, ret)
+        assert_equal(content, File.read("dst"))
+      end
+    }
+  end
+
   def test_copy_stream_smaller
     with_srccontent {|src, content|