Use of system cache

The implementor of callback handlers should be aware that by default Callback File System driver doesn't support buffered operations (i.e. system cache can't be used in callbacks)in order to speed up the operations. This means that

1. The callback handler procedure must avoid using any file operations in buffered mode (both explicit and implicit). All files, access to which is done from callbacks, should be opened with FILE_FLAG_NO_BUFFERING flag.
2. No APC (asynchronous procedure calls) should be performed.
3. User interface operations must be restricted.

Failure to follow the above restrictions will cause the system-wide deadlock.

If you need to perform any operations that involve or can involve system file cache, you need to set UseSystemCache property to true. This will slow down operations to some extent, however no deadlocks will occur.