#ifndef _NTIOAPI_H

typedef struct _FILE_FS_CONTROL_INFORMATION
{
    LARGE_INTEGER FreeSpaceStartFiltering;
    LARGE_INTEGER FreeSpaceThreshold;
    LARGE_INTEGER FreeSpaceStopFiltering;
    LARGE_INTEGER DefaultQuotaThreshold;
    LARGE_INTEGER DefaultQuotaLimit;
    ULONG FileSystemControlFlags; // FILE_VC_*
} FILE_FS_CONTROL_INFORMATION, *PFILE_FS_CONTROL_INFORMATION;

#endif
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This structure is documented in Windows Driver Kit.

Structure FILE_FS_CONTROL_INFORMATION is user as input and output buffers in calls to NtQueryVolumeInformationFile and NtSetVolumeInformationFile with information class set to FileFsControlInformation.

FreeSpaceStartFiltering

FreeSpaceThreshold

FreeSpaceStopFiltering

DefaultQuotaThreshold

DefaultQuotaLimit

FileSystemControlFlags

Documented by

Bo Branten

FILE_FS_CONTROL_INFORMATION - NtDoc