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Windows: Possible workaround for logarithmic slowdown for Encrypt-In-…
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…Place on large volumes (relates to #1063)

We replace absolute file pointer moving by relative moving with respect to current position. This was implemented as a workaround to address the performance issues related to in-place encryption. When using SetFilePointerEx() with FILE_BEGIN as the reference point, reaching the end of large drives during in-place encryption can cause significant slowdowns. By moving the file pointer relatively, these performance issues are mitigated.
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@idrassi
idrassi committed Jun 4, 2023
1 parent 3c68349 commit 2246653
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Showing 2 changed files with 52 additions and 21 deletions.
72 changes: 51 additions & 21 deletions src/Format/InPlace.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -593,7 +593,7 @@ int EncryptPartitionInPlaceBegin (volatile FORMAT_VOL_PARAMETERS *volParams, vol

offset.QuadPart = TC_VOLUME_DATA_OFFSET + dataAreaSize;

if (!SetFilePointerEx (dev, offset, NULL, FILE_BEGIN))
if (!MoveFilePointer (dev, offset))
{
nStatus = ERR_OS_ERROR;
goto closing_seq;
Expand Down Expand Up @@ -639,7 +639,7 @@ int EncryptPartitionInPlaceBegin (volatile FORMAT_VOL_PARAMETERS *volParams, vol

offset.QuadPart += TC_HIDDEN_VOLUME_HEADER_OFFSET;

if (!SetFilePointerEx (dev, offset, NULL, FILE_BEGIN))
if (!MoveFilePointer (dev, offset))
{
nStatus = ERR_OS_ERROR;
goto closing_seq;
Expand Down Expand Up @@ -916,7 +916,7 @@ int EncryptPartitionInPlaceResume (HANDLE dev,

offset.QuadPart = masterCryptoInfo->EncryptedAreaStart.Value - workChunkSize - TC_VOLUME_DATA_OFFSET;

if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0)
if (MoveFilePointer (dev, offset) == 0)
{
nStatus = ERR_OS_ERROR;
goto closing_seq;
Expand Down Expand Up @@ -1007,14 +1007,14 @@ int EncryptPartitionInPlaceResume (HANDLE dev,
memcpy (wipeRandCharsUpdate, wipeBuffer, sizeof (wipeRandCharsUpdate));
}

if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0
if (MoveFilePointer (dev, offset) == 0
|| WriteFile (dev, wipeBuffer, workChunkSize, &n, NULL) == 0)
{
// Write error
dwError = GetLastError();

// Undo failed write operation
if (workChunkSize > TC_VOLUME_DATA_OFFSET && SetFilePointerEx (dev, offset, NULL, FILE_BEGIN))
if (workChunkSize > TC_VOLUME_DATA_OFFSET && MoveFilePointer (dev, offset))
{
DecryptDataUnits ((byte *) buf, &unitNo, workChunkSize / ENCRYPTION_DATA_UNIT_SIZE, masterCryptoInfo);
WriteFile (dev, buf + TC_VOLUME_DATA_OFFSET, workChunkSize - TC_VOLUME_DATA_OFFSET, &n, NULL);
Expand All @@ -1034,7 +1034,7 @@ int EncryptPartitionInPlaceResume (HANDLE dev,

offset.QuadPart = masterCryptoInfo->EncryptedAreaStart.Value - workChunkSize;

if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0)
if (MoveFilePointer (dev, offset) == 0)
{
nStatus = ERR_OS_ERROR;
goto closing_seq;
Expand All @@ -1046,7 +1046,7 @@ int EncryptPartitionInPlaceResume (HANDLE dev,
dwError = GetLastError();

// Undo failed write operation
if (workChunkSize > TC_VOLUME_DATA_OFFSET && SetFilePointerEx (dev, offset, NULL, FILE_BEGIN))
if (workChunkSize > TC_VOLUME_DATA_OFFSET && MoveFilePointer (dev, offset))
{
DecryptDataUnits ((byte *) buf, &unitNo, workChunkSize / ENCRYPTION_DATA_UNIT_SIZE, masterCryptoInfo);
WriteFile (dev, buf + TC_VOLUME_DATA_OFFSET, workChunkSize - TC_VOLUME_DATA_OFFSET, &n, NULL);
Expand Down Expand Up @@ -1148,7 +1148,7 @@ int EncryptPartitionInPlaceResume (HANDLE dev,

offset.QuadPart = TC_VOLUME_HEADER_OFFSET;

if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0
if (MoveFilePointer (dev, offset) == 0
|| !WriteEffectiveVolumeHeader (TRUE, dev, (byte *) header))
{
nStatus = ERR_OS_ERROR;
Expand Down Expand Up @@ -1207,7 +1207,7 @@ int EncryptPartitionInPlaceResume (HANDLE dev,

offset.QuadPart += TC_HIDDEN_VOLUME_HEADER_OFFSET;

if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0
if (MoveFilePointer (dev, offset) == 0
|| !WriteEffectiveVolumeHeader (TRUE, dev, (byte *) header))
{
nStatus = ERR_OS_ERROR;
Expand Down Expand Up @@ -1544,7 +1544,7 @@ int DecryptPartitionInPlace (volatile FORMAT_VOL_PARAMETERS *volParams, volatile

offset.QuadPart = workChunkStartByteOffset;

if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0)
if (MoveFilePointer (dev, offset) == 0)
{
nStatus = ERR_OS_ERROR;
goto closing_seq;
Expand Down Expand Up @@ -1578,7 +1578,7 @@ int DecryptPartitionInPlace (volatile FORMAT_VOL_PARAMETERS *volParams, volatile

for (tmpSectorCount = workChunkSize / sectorSize; tmpSectorCount > 0; --tmpSectorCount)
{
if (SetFilePointerEx (dev, tmpSectorOffset, NULL, FILE_BEGIN) == 0)
if (MoveFilePointer (dev, tmpSectorOffset) == 0)
{
nStatus = ERR_OS_ERROR;
goto closing_seq;
Expand Down Expand Up @@ -1640,7 +1640,7 @@ int DecryptPartitionInPlace (volatile FORMAT_VOL_PARAMETERS *volParams, volatile

offset.QuadPart = workChunkStartByteOffset - TC_VOLUME_DATA_OFFSET;

if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0)
if (MoveFilePointer (dev, offset) == 0)
{
nStatus = ERR_OS_ERROR;
goto closing_seq;
Expand Down Expand Up @@ -1724,7 +1724,7 @@ int DecryptPartitionInPlace (volatile FORMAT_VOL_PARAMETERS *volParams, volatile
offset.QuadPart <= deviceSize - sectorSize;
offset.QuadPart += sectorSize)
{
if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0)
if (MoveFilePointer (dev, offset) == 0)
{
nStatus = ERR_OS_ERROR;
goto closing_seq;
Expand Down Expand Up @@ -1864,7 +1864,7 @@ int FastVolumeHeaderUpdate (HANDLE dev, CRYPTO_INFO *headerCryptoInfo, CRYPTO_IN

offset.QuadPart = deviceSize - TC_VOLUME_HEADER_GROUP_SIZE;

if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0
if (MoveFilePointer (dev, offset) == 0
|| !ReadEffectiveVolumeHeader (TRUE, dev, header, &n) || n < TC_VOLUME_HEADER_EFFECTIVE_SIZE)
{
nStatus = ERR_OS_ERROR;
Expand Down Expand Up @@ -1913,7 +1913,7 @@ int FastVolumeHeaderUpdate (HANDLE dev, CRYPTO_INFO *headerCryptoInfo, CRYPTO_IN
EncryptBuffer (header + HEADER_ENCRYPTED_DATA_OFFSET, HEADER_ENCRYPTED_DATA_SIZE, pCryptoInfo);


if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0
if (MoveFilePointer (dev, offset) == 0
|| !WriteEffectiveVolumeHeader (TRUE, dev, header))
{
nStatus = ERR_OS_ERROR;
Expand Down Expand Up @@ -2092,7 +2092,7 @@ static int ConcealNTFS (HANDLE dev)

offset.QuadPart = 0;

if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0)
if (MoveFilePointer (dev, offset) == 0)
return ERR_OS_ERROR;

if (ReadFile (dev, buf, TC_INITIAL_NTFS_CONCEAL_PORTION_SIZE, &nbrBytesProcessed, NULL) == 0)
Expand All @@ -2103,7 +2103,7 @@ static int ConcealNTFS (HANDLE dev)

offset.QuadPart = 0;

if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0)
if (MoveFilePointer (dev, offset) == 0)
return ERR_OS_ERROR;

if (WriteFile (dev, buf, TC_INITIAL_NTFS_CONCEAL_PORTION_SIZE, &nbrBytesProcessed, NULL) == 0)
Expand All @@ -2122,7 +2122,7 @@ static int ConcealNTFS (HANDLE dev)
{
Sleep (1);
}
while (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0
while (MoveFilePointer (dev, offset) == 0
|| WriteFile (dev, buf, TC_INITIAL_NTFS_CONCEAL_PORTION_SIZE, &nbrBytesProcessed2, NULL) == 0);

SetLastError (dwError);
Expand Down Expand Up @@ -2198,6 +2198,35 @@ BOOL SaveNonSysInPlaceEncSettings (int delta, WipeAlgorithmId newWipeAlgorithm,
return SaveBufferToFile (str, GetConfigPath (TC_APPD_FILENAME_NONSYS_INPLACE_ENC), (DWORD) strlen(str), FALSE, FALSE);
}

// This function moves the file pointer to the given offset. It first retrieves the current
// file position using SetFilePointerEx() with FILE_CURRENT as the reference point, and then
// calculates the difference between the current position and the desired position. Subsequently,
// it moves the file pointer by the difference calculated using SetFilePointerEx() again.
//
// This approach of moving the file pointer relatively (instead of absolutely) was implemented
// as a workaround to address the performance issues related to in-place encryption. When using
// SetFilePointerEx() with FILE_BEGIN as the reference point, reaching the end of large drives
// during in-place encryption can cause significant slowdowns. By moving the file pointer
// relatively, these performance issues are mitigated.
BOOL MoveFilePointer (HANDLE dev, LARGE_INTEGER offset)
{
LARGE_INTEGER currOffset;
LARGE_INTEGER diffOffset;

currOffset.QuadPart = 0;
if (SetFilePointerEx (dev, currOffset, &currOffset, FILE_CURRENT) == 0)
return FALSE;

diffOffset.QuadPart = offset.QuadPart - currOffset.QuadPart;
if (diffOffset.QuadPart == 0)
return TRUE;

// Moves the file pointer by the difference between current and desired positions
if (SetFilePointerEx (dev, diffOffset, NULL, FILE_CURRENT) == 0)
return FALSE;

return TRUE;
}

// Repairs damaged sectors (i.e. those with read errors) by zeroing them.
// Note that this operating fails if there are any write errors.
Expand All @@ -2217,7 +2246,7 @@ int ZeroUnreadableSectors (HANDLE dev, LARGE_INTEGER startOffset, int64 size, in
if (!sectorBuffer)
return ERR_OUTOFMEMORY;

if (SetFilePointerEx (dev, startOffset, NULL, FILE_BEGIN) == 0)
if (!MoveFilePointer(dev, workOffset))
{
nStatus = ERR_OS_ERROR;
goto closing_seq;
Expand All @@ -2230,7 +2259,8 @@ int ZeroUnreadableSectors (HANDLE dev, LARGE_INTEGER startOffset, int64 size, in
{
memset (sectorBuffer, 0, sectorSize);

if (SetFilePointerEx (dev, workOffset, NULL, FILE_BEGIN) == 0)
// If ReadFile failed, move back to start of the unreadable sector
if (MoveFilePointer (dev, workOffset) == 0)
{
nStatus = ERR_OS_ERROR;
goto closing_seq;
Expand Down Expand Up @@ -2281,7 +2311,7 @@ static int OpenBackupHeader (HANDLE dev, const wchar_t *devicePath, Password *pa

offset.QuadPart = deviceSize - TC_VOLUME_HEADER_GROUP_SIZE;

if (SetFilePointerEx (dev, offset, NULL, FILE_BEGIN) == 0
if (MoveFilePointer (dev, offset) == 0
|| !ReadEffectiveVolumeHeader (TRUE, dev, (byte *) header, &n) || n < TC_VOLUME_HEADER_EFFECTIVE_SIZE)
{
nStatus = ERR_OS_ERROR;
Expand Down
1 change: 1 addition & 0 deletions src/Format/InPlace.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,7 @@ static int DismountFileSystem (HWND hwndDlg, HANDLE dev, int driveLetter, BOOL b
static int ConcealNTFS (HANDLE dev);
BOOL SaveNonSysInPlaceEncSettings (int delta, WipeAlgorithmId wipeAlgorithm, BOOL bDecrypting);
static void ExportProgressStats (__int64 bytesDone, __int64 totalSize);
BOOL MoveFilePointer (HANDLE dev, LARGE_INTEGER offset);
int ZeroUnreadableSectors (HANDLE dev, LARGE_INTEGER startOffset, int64 size, int sectorSize, uint64 *zeroedSectorCount);
static int OpenBackupHeader (HANDLE dev, const wchar_t *devicePath, Password *password, int pkcs5, int pim, PCRYPTO_INFO *retCryptoInfo, CRYPTO_INFO *headerCryptoInfo, __int64 deviceSize);
BOOL MoveClustersBeforeThreshold (HANDLE volumeHandle, PWSTR volumeDevicePath, int64 clusterThreshold);
Expand Down

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