rbd-replay: handle EOF gracefully

Fixes: #14452
Signed-off-by: Mykola Golub <mgolub@mirantis.com>
(cherry picked from commit c59b84c)

src/rbd_replay/BufferReader.cc

@@ -9,19 +9,22 @@ namespace rbd_replay {
 
 BufferReader::BufferReader(int fd, size_t min_bytes, size_t max_bytes)
   : m_fd(fd), m_min_bytes(min_bytes), m_max_bytes(max_bytes),
-    m_bl_it(m_bl.begin()) {
+    m_bl_it(m_bl.begin()), m_eof_reached(false) {
   assert(m_min_bytes <= m_max_bytes);
 }
 
 int BufferReader::fetch(bufferlist::iterator **it) {
   if (m_bl_it.get_remaining() < m_min_bytes) {
     ssize_t bytes_to_read = ROUND_UP_TO(m_max_bytes - m_bl_it.get_remaining(),
                                         CEPH_BUFFER_APPEND_SIZE);
-    while (bytes_to_read > 0) {
+    while (!m_eof_reached && bytes_to_read > 0) {
       int r = m_bl.read_fd(m_fd, CEPH_BUFFER_APPEND_SIZE);
       if (r < 0) {
         return r;
       }
+      if (r == 0) {
+	m_eof_reached = true;
+      }
       assert(r <= bytes_to_read);
       bytes_to_read -= r;
     }

src/rbd_replay/BufferReader.h

@@ -25,6 +25,7 @@ class BufferReader {
   size_t m_max_bytes;
   bufferlist m_bl;
   bufferlist::iterator m_bl_it;
+  bool m_eof_reached;
 
 };
 

src/rbd_replay/Replayer.cc

@@ -224,14 +224,17 @@ void Replayer::run(const std::string& replay_file) {
                       << std::endl;
             exit(-r);
           }
+	  if (it->get_remaining() == 0) {
+	    break;
+	  }
 
           if (versioned) {
             action_entry.decode(*it);
           } else {
             action_entry.decode_unversioned(*it);
           }
         } catch (const buffer::error &err) {
-          std::cerr << "Failed to decode trace action" << std::endl;
+          std::cerr << "Failed to decode trace action: " << err.what() << std::endl;
           exit(1);
         }