typedef struct _CACHE_MANAGER_CALLBACKS
{
     UCHAR * AcquireForLazyWrite;
     PVOID ReleaseFromLazyWrite;
     UCHAR * AcquireForReadAhead;
     PVOID ReleaseFromReadAhead;
} CACHE_MANAGER_CALLBACKS, *PCACHE_MANAGER_CALLBACKS;

Windows Vista Kernel Structures