race-condition safe implementation of mi_delete_table/maria_delete_table

Author: vuvova

include/my_sys.h

@@ -581,6 +581,9 @@ extern File my_create_with_symlink(const char *linkname, const char *filename,
 extern int my_delete_with_symlink(const char *name, myf MyFlags);
 extern int my_rename_with_symlink(const char *from,const char *to,myf MyFlags);
 extern int my_symlink(const char *content, const char *linkname, myf MyFlags);
+extern int my_handler_delete_with_symlink(PSI_file_key key, const char *name,
+                                          const char *ext, myf sync_dir);
+
 extern size_t my_read(File Filedes,uchar *Buffer,size_t Count,myf MyFlags);
 extern size_t my_pread(File Filedes,uchar *Buffer,size_t Count,my_off_t offset,
 		     myf MyFlags);

mysys/my_symlink2.c

@@ -182,3 +182,31 @@ int my_rename_with_symlink(const char *from, const char *to, myf MyFlags)
   DBUG_RETURN(result);
 #endif /* HAVE_READLINK */
 }
+
+/** delete a - possibly symlinked - table file
+
+  This is used to delete a file that is part of a table (e.g. MYI or MYD
+  file of MyISAM) when dropping a table. A file might be a symlink -
+  if the table was created with DATA DIRECTORY or INDEX DIRECTORY -
+  in this case both the symlink and the symlinked file are deleted,
+  but only if the symlinked file is not in the datadir.
+*/
+int my_handler_delete_with_symlink(PSI_file_key key, const char *name,
+                                   const char *ext, myf sync_dir)
+{
+  char orig[FN_REFLEN], real[FN_REFLEN];
+  int res= 0;
+  DBUG_ENTER("my_handler_delete_with_symlink");
+
+  fn_format(orig, name, "", ext, MY_UNPACK_FILENAME | MY_APPEND_EXT);
+  if (my_is_symlink(orig))
+  {
+    /*
+      Delete the symlinked file only if the symlink is not
+      pointing into datadir.
+    */
+    if (!(my_realpath(real, orig, MYF(0)) || mysys_test_invalid_symlink(real)))
+      res= mysql_file_delete(key, real, MYF(MY_NOSYMLINKS | MY_WME | sync_dir));
+  }
+  DBUG_RETURN(mysql_file_delete(key, orig, MYF(MY_WME | sync_dir)) || res);
+}

mysys/my_sync.c

@@ -199,7 +199,7 @@ int my_sync_dir_by_file(const char *file_name __attribute__((unused)),
   char dir_name[FN_REFLEN];
   size_t dir_name_length;
   dirname_part(dir_name, file_name, &dir_name_length);
-  return my_sync_dir(dir_name, my_flags);
+  return my_sync_dir(dir_name, my_flags & ~MY_NOSYMLINKS);
 #else
   return 0;
 #endif

storage/maria/ma_delete_table.c

@@ -84,15 +84,10 @@ int maria_delete_table(const char *name)
 
 int maria_delete_table_files(const char *name, myf sync_dir)
 {
-  char from[FN_REFLEN];
   DBUG_ENTER("maria_delete_table_files");
 
-  fn_format(from,name,"",MARIA_NAME_IEXT,MY_UNPACK_FILENAME|MY_APPEND_EXT);
-  if (mysql_file_delete_with_symlink(key_file_kfile, from,
-                                     MYF(MY_WME | sync_dir)))
+  if (my_handler_delete_with_symlink(key_file_kfile, name, MARIA_NAME_IEXT, sync_dir) ||
+      my_handler_delete_with_symlink(key_file_dfile, name, MARIA_NAME_DEXT, sync_dir))
     DBUG_RETURN(my_errno);
-  fn_format(from,name,"",MARIA_NAME_DEXT,MY_UNPACK_FILENAME|MY_APPEND_EXT);
-  DBUG_RETURN(mysql_file_delete_with_symlink(key_file_dfile,
-                                             from, MYF(MY_WME | sync_dir)) ?
-              my_errno : 0);
+  DBUG_RETURN(0);
 }

storage/myisam/mi_delete_table.c

@@ -22,42 +22,14 @@
 
 int mi_delete_table(const char *name)
 {
-  char from[FN_REFLEN];
   DBUG_ENTER("mi_delete_table");
 
 #ifdef EXTRA_DEBUG
   check_table_is_closed(name,"delete");
 #endif
 
-  fn_format(from,name,"",MI_NAME_IEXT,MY_UNPACK_FILENAME|MY_APPEND_EXT);
-  if (my_is_symlink(from) && mysys_test_invalid_symlink(from))
-  {
-    /*
-      Symlink is pointing to file in data directory.
-      Remove symlink, keep file.
-    */
-    if (mysql_file_delete(mi_key_file_kfile, from, MYF(MY_WME)))
-      DBUG_RETURN(my_errno);
-  }
-  else
-  {
-    if (mysql_file_delete_with_symlink(mi_key_file_kfile, from, MYF(MY_WME)))
-      DBUG_RETURN(my_errno);
-  }
-  fn_format(from,name,"",MI_NAME_DEXT,MY_UNPACK_FILENAME|MY_APPEND_EXT);
-  if (my_is_symlink(from) && mysys_test_invalid_symlink(from))
-  {
-    /*
-      Symlink is pointing to file in data directory.
-      Remove symlink, keep file.
-    */
-    if (mysql_file_delete(mi_key_file_dfile, from, MYF(MY_WME)))
-      DBUG_RETURN(my_errno);
-  }
-  else
-  {
-    if (mysql_file_delete_with_symlink(mi_key_file_dfile, from, MYF(MY_WME)))
-      DBUG_RETURN(my_errno);
-  }
+  if (my_handler_delete_with_symlink(mi_key_file_kfile, name, MI_NAME_IEXT, 0) ||
+      my_handler_delete_with_symlink(mi_key_file_dfile, name, MI_NAME_DEXT, 0))
+    DBUG_RETURN(my_errno);
   DBUG_RETURN(0);
 }