MDEV-17133 dump thread reads from a past positionbb-10.1-MDEV-17133

2 files changed, 79 insertions, 3 deletions

diff --git a/mysys/mf_iocache.c b/mysys/mf_iocache.c
index 56b1ae3fc6e..8f829a8c9c2 100644
--- a/mysys/mf_iocache.c
+++ b/mysys/mf_iocache.c
@@ -563,7 +563,7 @@ int _my_b_write(IO_CACHE *info, const uchar *Buffer, size_t Count)
 
 int _my_b_cache_read(IO_CACHE *info, uchar *Buffer, size_t Count)
 {
-  size_t length, diff_length, left_length= 0, max_length;
+  size_t length= 0, diff_length, left_length= 0, max_length;
   my_off_t pos_in_file;
   DBUG_ENTER("_my_b_cache_read");
 
@@ -668,7 +668,11 @@ int _my_b_cache_read(IO_CACHE *info, uchar *Buffer, size_t Count)
     else
     {
       info->error= 0;
-      DBUG_RETURN(0);                           /* EOF */
+      if (length == 0)
+      {
+        DBUG_RETURN(0);  // EOF
+      }
+      length= 0;
     }
   }
   else if ((length= mysql_file_read(info->file,info->buffer, max_length,
diff --git a/unittest/sql/mf_iocache-t.cc b/unittest/sql/mf_iocache-t.cc
index 8f97745f0fc..3de80ab83f9 100644
--- a/unittest/sql/mf_iocache-t.cc
+++ b/unittest/sql/mf_iocache-t.cc
@@ -285,11 +285,82 @@ void mdev14014()
   close_cached_file(&info);
 }
 
+void mdev17133()
+{
+  int   res, eof_iter=16, read_iter= 16;
+  uchar buf_i[1024*256];      // read
+  uchar buf_o[sizeof(buf_i)]; // write
+  const size_t eof_block_size= sizeof(buf_o) / eof_iter;
+  const size_t read_size= eof_block_size / read_iter;
+  size_t total;
+
+  memset(buf_i,    0, sizeof( buf_i));
+  memset(buf_o, FILL, sizeof(buf_o));
+
+  diag("MDEV-17133 Dump thread reads from the past");
+
+  init_io_cache_encryption();
+
+  res= open_cached_file(&info, 0, 0, CACHE_SIZE, 0);
+  ok(res == 0, "open_cached_file" INFO_TAIL);
+
+  res= my_b_write(&info, buf_o, sizeof(buf_o));
+  ok(res == 0, "buffer is written" INFO_TAIL);
+  res= my_b_tell(&info);
+  ok(res == sizeof(buf_o), "cache size as expected");
+
+  res= my_b_flush_io_cache(&info, 1);
+  ok(res == 0, "flush" INFO_TAIL);
+  res= reinit_io_cache(&info, READ_CACHE, 0, 0, 0);
+  ok(res == 0, "reinit READ_CACHE" INFO_TAIL);
+
+  // read by chunks of variable size eof_iter times
+  for (info.end_of_file=0, total= 0; eof_iter; eof_iter--)
+  {
+    int i;
+    size_t curr_read_size;
+    info.end_of_file=
+      eof_iter == 1 ? sizeof(buf_o) :
+      MY_MIN(sizeof(buf_o),
+             info.end_of_file + eof_block_size +
+             // plus 10% of randomization to the average
+             (eof_block_size/10 - rand() % (eof_block_size/5)));
+
+    // read a chunk by blocks of variable size read_iter times
+    for (i= 0; i < read_iter; i++, total += curr_read_size)
+    {
+      curr_read_size=
+        i == read_iter - 1 ? info.end_of_file - total :
+        MY_MIN(info.end_of_file - total,
+               read_size + read_size/10 - rand() % (read_size/5));
+
+      res= my_b_read(&info, buf_i + total, MY_MIN(19, curr_read_size));
+      ok(res == 0, "read of 19");
+      // TODO: mark read bytes in the used part of the cache buffer
+
+      // random size 2nd read
+      res= my_b_read(&info, buf_i + total + MY_MIN(19, curr_read_size),
+                     19 >= curr_read_size ? 0 : curr_read_size - 19);
+      ok(res == 0, "rest of read");
+      // TODO: Check that no marked bytes are in the read buffer
+      // TODO: mark read bytes in the used part of the cache buffer
+
+    }
+    ok(info.pos_in_file + (info.read_end - info.buffer) == info.end_of_file,
+       "cache is read up to eof");
+    ok(total == info.end_of_file, "total matches eof");
+  }
+  ok(total == sizeof(buf_i), "read total size match");
+  ok(buf_i[sizeof(buf_i) - 1] == FILL, "data read correctly");
+
+  close_cached_file(&info);
+}
+
 
 int main(int argc __attribute__((unused)),char *argv[])
 {
   MY_INIT(argv[0]);
-  plan(51);
+  plan(602);
 
   /* temp files with and without encryption */
   encrypt_tmp_files= 1;
@@ -306,6 +377,7 @@ int main(int argc __attribute__((unused)),char *argv[])
   encrypt_tmp_files= 0;
 
   mdev14014();
+  mdev17133();
 
   my_end(0);
   return exit_status();