This allows querying volume information without issuing an IRP to the owner device.
The kernel is supposed to already have all the required information to return
to the caller.
Side effect: this allows querying volume information for devices not implementing
IRP_MJ_QUERY_VOLUME_INFORMATION such as null.sys
This fixes opening null device in Python.
Fix based on debugging by Maxim Smirnov in PR #1442
CORE-14551
This quick check based on bits and operation is for 2^ based
sector sizes (most of the cases) and will perform faster than
the modulo operation which is still used in fallback in case
the sector size wouldn't be a power of 2.
For user mode, when probing output buffer, if it's null, length
will also be set to 0.
This avoids user mode applications being able to trigger various
asserts in ReactOS (and thus BSOD when no debugger is plugged ;-)).
The reserve IRP is an IRP which is allocated on system boot and kept during
the whole system life. Its purpose is to allow page reads in case of
low-memory situations where the system doesn't have enough memory left
to allocate an IRP to read from the page file (would be catastrophic situation).
