/* $Id: VDVfs.cpp 93115 2022-01-01 11:31:46Z vboxsync $ */ /** @file * Virtual Disk Container implementation. - VFS glue. */ /* * Copyright (C) 2012-2022 Oracle Corporation * * This file is part of VirtualBox Open Source Edition (OSE), as * available from http://www.virtualbox.org. This file is free software; * you can redistribute it and/or modify it under the terms of the GNU * General Public License (GPL) as published by the Free Software * Foundation, in version 2 as it comes in the "COPYING" file of the * VirtualBox OSE distribution. VirtualBox OSE is distributed in the * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind. */ /********************************************************************************************************************************* * Header Files * *********************************************************************************************************************************/ #include #include #include #include #include #include #include #include #include #include #include #include "VDInternal.h" /********************************************************************************************************************************* * Structures and Typedefs * *********************************************************************************************************************************/ /** * The internal data of a DVM volume I/O stream. */ typedef struct VDVFSFILE { /** The volume the VFS file belongs to. */ PVDISK pDisk; /** Current position. */ uint64_t offCurPos; /** Flags given during creation. */ uint32_t fFlags; } VDVFSFILE; /** Pointer to a the internal data of a DVM volume file. */ typedef VDVFSFILE *PVDVFSFILE; /** * VD read helper taking care of unaligned accesses. * * @return VBox status code. * @param pDisk VD disk container. * @param off Offset to start reading from. * @param pvBuf Pointer to the buffer to read into. * @param cbRead Amount of bytes to read. */ static int vdReadHelper(PVDISK pDisk, uint64_t off, void *pvBuf, size_t cbRead) { int rc; /* Take direct route if the request is sector aligned. */ uint64_t const offMisalign = off & 511; size_t const cbMisalign = (off + cbRead) & 511; if ( !offMisalign && !cbMisalign) rc = VDRead(pDisk, off, pvBuf, cbRead); else { uint8_t *pbBuf = (uint8_t *)pvBuf; uint8_t abBuf[512]; /* Unaligned buffered read of head. Aligns the offset. */ if (offMisalign) { rc = VDRead(pDisk, off - offMisalign, abBuf, 512); if (RT_SUCCESS(rc)) { size_t const cbPart = RT_MIN(512 - offMisalign, cbRead); memcpy(pbBuf, &abBuf[offMisalign], cbPart); pbBuf += cbPart; off += cbPart; cbRead -= cbPart; } } else rc = VINF_SUCCESS; /* Aligned direct read. */ if ( RT_SUCCESS(rc) && cbRead >= 512) { Assert(!(off % 512)); size_t cbPart = cbRead - cbMisalign; Assert(!(cbPart % 512)); rc = VDRead(pDisk, off, pbBuf, cbPart); if (RT_SUCCESS(rc)) { pbBuf += cbPart; off += cbPart; cbRead -= cbPart; } } /* Unaligned buffered read of tail. */ if ( RT_SUCCESS(rc) && cbRead) { Assert(cbRead == cbMisalign); Assert(cbRead < 512); Assert(!(off % 512)); rc = VDRead(pDisk, off, abBuf, 512); if (RT_SUCCESS(rc)) memcpy(pbBuf, abBuf, cbRead); } } return rc; } /** * VD write helper taking care of unaligned accesses. * * @return VBox status code. * @param pDisk VD disk container. * @param off Offset to start writing to. * @param pvSrc Pointer to the buffer to read from. * @param cbWrite Amount of bytes to write. */ static int vdWriteHelper(PVDISK pDisk, uint64_t off, const void *pvSrc, size_t cbWrite) { uint8_t const *pbSrc = (uint8_t const *)pvSrc; uint8_t abBuf[4096]; int rc; /* * Take direct route if the request is sector aligned. */ uint64_t const offMisalign = off & 511; size_t const cbMisalign = (off + cbWrite) & 511; if ( !offMisalign && !cbMisalign) { if (RTListIsEmpty(&pDisk->ListFilterChainWrite)) rc = VDWrite(pDisk, off, pbSrc, cbWrite); else { /* Filtered writes must be double buffered as the filter may need to modify the input buffer directly. */ do { size_t cbThisWrite = RT_MIN(cbWrite, sizeof(abBuf)); rc = VDWrite(pDisk, off, memcpy(abBuf, pbSrc, cbThisWrite), cbThisWrite); if (RT_SUCCESS(rc)) { pbSrc += cbThisWrite; off += cbThisWrite; cbWrite -= cbThisWrite; } else break; } while (cbWrite > 0); } } else { /* * Unaligned buffered read+write of head. Aligns the offset. */ if (offMisalign) { rc = VDRead(pDisk, off - offMisalign, abBuf, 512); if (RT_SUCCESS(rc)) { size_t const cbPart = RT_MIN(512 - offMisalign, cbWrite); memcpy(&abBuf[offMisalign], pbSrc, cbPart); rc = VDWrite(pDisk, off - offMisalign, abBuf, 512); if (RT_SUCCESS(rc)) { pbSrc += cbPart; off += cbPart; cbWrite -= cbPart; } } } else rc = VINF_SUCCESS; /* * Aligned direct write. */ if ( RT_SUCCESS(rc) && cbWrite >= 512) { Assert(!(off % 512)); size_t cbPart = cbWrite - cbMisalign; Assert(!(cbPart % 512)); if (RTListIsEmpty(&pDisk->ListFilterChainWrite)) { rc = VDWrite(pDisk, off, pbSrc, cbPart); if (RT_SUCCESS(rc)) { pbSrc += cbPart; off += cbPart; cbWrite -= cbPart; } } else { /* Filtered writes must be double buffered as the filter may need to modify the input buffer directly. */ do { size_t cbThisWrite = RT_MIN(cbPart, sizeof(abBuf)); rc = VDWrite(pDisk, off, memcpy(abBuf, pbSrc, cbThisWrite), cbThisWrite); if (RT_SUCCESS(rc)) { pbSrc += cbThisWrite; off += cbThisWrite; cbWrite -= cbThisWrite; cbPart -= cbThisWrite; } else break; } while (cbPart > 0); } } /* * Unaligned buffered read+write of tail. */ if ( RT_SUCCESS(rc) && cbWrite > 0) { Assert(cbWrite == cbMisalign); Assert(cbWrite < 512); Assert(!(off % 512)); rc = VDRead(pDisk, off, abBuf, 512); if (RT_SUCCESS(rc)) { memcpy(abBuf, pbSrc, cbWrite); rc = VDWrite(pDisk, off, abBuf, 512); } } } return rc; } /** * @interface_method_impl{RTVFSOBJOPS,pfnClose} */ static DECLCALLBACK(int) vdVfsFile_Close(void *pvThis) { PVDVFSFILE pThis = (PVDVFSFILE)pvThis; if (pThis->fFlags & VD_VFSFILE_DESTROY_ON_RELEASE) VDDestroy(pThis->pDisk); return VINF_SUCCESS; } /** * @interface_method_impl{RTVFSOBJOPS,pfnQueryInfo} */ static DECLCALLBACK(int) vdVfsFile_QueryInfo(void *pvThis, PRTFSOBJINFO pObjInfo, RTFSOBJATTRADD enmAddAttr) { PVDVFSFILE pThis = (PVDVFSFILE)pvThis; unsigned const cOpenImages = VDGetCount(pThis->pDisk); pObjInfo->cbObject = VDGetSize(pThis->pDisk, cOpenImages - 1); pObjInfo->cbAllocated = 0; for (unsigned iImage = 0; iImage < cOpenImages; iImage++) pObjInfo->cbAllocated += VDGetFileSize(pThis->pDisk, iImage); /** @todo enumerate the disk images directly... */ RTTimeNow(&pObjInfo->AccessTime); pObjInfo->BirthTime = pObjInfo->AccessTime; pObjInfo->ChangeTime = pObjInfo->AccessTime; pObjInfo->ModificationTime = pObjInfo->AccessTime; pObjInfo->Attr.fMode = RTFS_DOS_NT_NORMAL | RTFS_TYPE_FILE | 0644; pObjInfo->Attr.enmAdditional = enmAddAttr; switch (enmAddAttr) { case RTFSOBJATTRADD_UNIX: pObjInfo->Attr.u.Unix.uid = NIL_RTUID; pObjInfo->Attr.u.Unix.gid = NIL_RTGID; pObjInfo->Attr.u.Unix.cHardlinks = 1; pObjInfo->Attr.u.Unix.INodeIdDevice = 0; pObjInfo->Attr.u.Unix.INodeId = 0; pObjInfo->Attr.u.Unix.fFlags = 0; pObjInfo->Attr.u.Unix.GenerationId = 0; pObjInfo->Attr.u.Unix.Device = 0; break; case RTFSOBJATTRADD_UNIX_OWNER: pObjInfo->Attr.u.UnixOwner.uid = NIL_RTUID; pObjInfo->Attr.u.UnixOwner.szName[0] = '\0'; break; case RTFSOBJATTRADD_UNIX_GROUP: pObjInfo->Attr.u.UnixGroup.gid = NIL_RTGID; pObjInfo->Attr.u.UnixGroup.szName[0] = '\0'; break; case RTFSOBJATTRADD_EASIZE: pObjInfo->Attr.u.EASize.cb = 0; break; default: AssertFailedReturn(VERR_INVALID_PARAMETER); } return VINF_SUCCESS; } /** * @interface_method_impl{RTVFSIOSTREAMOPS,pfnRead} */ static DECLCALLBACK(int) vdVfsFile_Read(void *pvThis, RTFOFF off, PCRTSGBUF pSgBuf, bool fBlocking, size_t *pcbRead) { PVDVFSFILE pThis = (PVDVFSFILE)pvThis; Assert(pSgBuf->cSegs == 1); NOREF(fBlocking); /* * Find the current position and check if it's within the volume. */ uint64_t offUnsigned = off < 0 ? pThis->offCurPos : (uint64_t)off; uint64_t const cbImage = VDGetSize(pThis->pDisk, VD_LAST_IMAGE); if (offUnsigned >= cbImage) { if (pcbRead) { *pcbRead = 0; pThis->offCurPos = cbImage; return VINF_EOF; } return VERR_EOF; } int rc = VINF_SUCCESS; size_t cbLeftToRead = pSgBuf->paSegs[0].cbSeg; if (offUnsigned + cbLeftToRead <= cbImage) { if (pcbRead) *pcbRead = cbLeftToRead; } else { if (!pcbRead) return VERR_EOF; *pcbRead = cbLeftToRead = (size_t)(cbImage - offUnsigned); rc = VINF_EOF; } /* * Ok, we've got a valid stretch within the file. Do the reading. */ if (cbLeftToRead > 0) { int rc2 = vdReadHelper(pThis->pDisk, offUnsigned, pSgBuf->paSegs[0].pvSeg, cbLeftToRead); if (RT_SUCCESS(rc2)) offUnsigned += cbLeftToRead; else rc = rc2; } pThis->offCurPos = offUnsigned; return rc; } /** * @interface_method_impl{RTVFSIOSTREAMOPS,pfnWrite} */ static DECLCALLBACK(int) vdVfsFile_Write(void *pvThis, RTFOFF off, PCRTSGBUF pSgBuf, bool fBlocking, size_t *pcbWritten) { PVDVFSFILE pThis = (PVDVFSFILE)pvThis; Assert(pSgBuf->cSegs == 1); NOREF(fBlocking); /* * Find the current position and check if it's within the volume. * Writing beyond the end of a volume is not supported. */ uint64_t offUnsigned = off < 0 ? pThis->offCurPos : (uint64_t)off; uint64_t const cbImage = VDGetSize(pThis->pDisk, VD_LAST_IMAGE); if (offUnsigned >= cbImage) { if (pcbWritten) { *pcbWritten = 0; pThis->offCurPos = cbImage; } return VERR_EOF; } size_t cbLeftToWrite; if (offUnsigned + pSgBuf->paSegs[0].cbSeg <= cbImage) { cbLeftToWrite = pSgBuf->paSegs[0].cbSeg; if (pcbWritten) *pcbWritten = cbLeftToWrite; } else { if (!pcbWritten) return VERR_EOF; *pcbWritten = cbLeftToWrite = (size_t)(cbImage - offUnsigned); } /* * Ok, we've got a valid stretch within the file. Do the reading. */ int rc = VINF_SUCCESS; if (cbLeftToWrite > 0) { rc = vdWriteHelper(pThis->pDisk, offUnsigned, pSgBuf->paSegs[0].pvSeg, cbLeftToWrite); if (RT_SUCCESS(rc)) offUnsigned += cbLeftToWrite; } pThis->offCurPos = offUnsigned; return rc; } /** * @interface_method_impl{RTVFSIOSTREAMOPS,pfnFlush} */ static DECLCALLBACK(int) vdVfsFile_Flush(void *pvThis) { PVDVFSFILE pThis = (PVDVFSFILE)pvThis; return VDFlush(pThis->pDisk); } /** * @interface_method_impl{RTVFSIOSTREAMOPS,pfnTell} */ static DECLCALLBACK(int) vdVfsFile_Tell(void *pvThis, PRTFOFF poffActual) { PVDVFSFILE pThis = (PVDVFSFILE)pvThis; *poffActual = pThis->offCurPos; return VINF_SUCCESS; } /** * @interface_method_impl{RTVFSOBJSETOPS,pfnSetMode} */ static DECLCALLBACK(int) vdVfsFile_SetMode(void *pvThis, RTFMODE fMode, RTFMODE fMask) { NOREF(pvThis); NOREF(fMode); NOREF(fMask); return VERR_NOT_SUPPORTED; } /** * @interface_method_impl{RTVFSOBJSETOPS,pfnSetTimes} */ static DECLCALLBACK(int) vdVfsFile_SetTimes(void *pvThis, PCRTTIMESPEC pAccessTime, PCRTTIMESPEC pModificationTime, PCRTTIMESPEC pChangeTime, PCRTTIMESPEC pBirthTime) { NOREF(pvThis); NOREF(pAccessTime); NOREF(pModificationTime); NOREF(pChangeTime); NOREF(pBirthTime); return VERR_NOT_SUPPORTED; } /** * @interface_method_impl{RTVFSOBJSETOPS,pfnSetOwner} */ static DECLCALLBACK(int) vdVfsFile_SetOwner(void *pvThis, RTUID uid, RTGID gid) { NOREF(pvThis); NOREF(uid); NOREF(gid); return VERR_NOT_SUPPORTED; } /** * @interface_method_impl{RTVFSFILEOPS,pfnSeek} */ static DECLCALLBACK(int) vdVfsFile_Seek(void *pvThis, RTFOFF offSeek, unsigned uMethod, PRTFOFF poffActual) { PVDVFSFILE pThis = (PVDVFSFILE)pvThis; /* * Seek relative to which position. */ uint64_t offWrt; switch (uMethod) { case RTFILE_SEEK_BEGIN: offWrt = 0; break; case RTFILE_SEEK_CURRENT: offWrt = pThis->offCurPos; break; case RTFILE_SEEK_END: offWrt = VDGetSize(pThis->pDisk, VD_LAST_IMAGE); break; default: return VERR_INTERNAL_ERROR_5; } /* * Calc new position, take care to stay without bounds. */ uint64_t offNew; if (offSeek == 0) offNew = offWrt; else if (offSeek > 0) { offNew = offWrt + offSeek; if ( offNew < offWrt || offNew > RTFOFF_MAX) offNew = RTFOFF_MAX; } else if ((uint64_t)-offSeek < offWrt) offNew = offWrt + offSeek; else offNew = 0; /* * Update the state and set return value. */ pThis->offCurPos = offNew; *poffActual = offNew; return VINF_SUCCESS; } /** * @interface_method_impl{RTVFSFILEOPS,pfnQuerySize} */ static DECLCALLBACK(int) vdVfsFile_QuerySize(void *pvThis, uint64_t *pcbFile) { PVDVFSFILE pThis = (PVDVFSFILE)pvThis; *pcbFile = VDGetSize(pThis->pDisk, VD_LAST_IMAGE); return VINF_SUCCESS; } /** * Standard file operations. */ DECL_HIDDEN_CONST(const RTVFSFILEOPS) g_vdVfsStdFileOps = { { /* Stream */ { /* Obj */ RTVFSOBJOPS_VERSION, RTVFSOBJTYPE_FILE, "VDFile", vdVfsFile_Close, vdVfsFile_QueryInfo, RTVFSOBJOPS_VERSION }, RTVFSIOSTREAMOPS_VERSION, RTVFSIOSTREAMOPS_FEAT_NO_SG, vdVfsFile_Read, vdVfsFile_Write, vdVfsFile_Flush, NULL /*PollOne*/, vdVfsFile_Tell, NULL /*Skip*/, NULL /*ZeroFill*/, RTVFSIOSTREAMOPS_VERSION, }, RTVFSFILEOPS_VERSION, /*RTVFSIOFILEOPS_FEAT_NO_AT_OFFSET*/ 0, { /* ObjSet */ RTVFSOBJSETOPS_VERSION, RT_UOFFSETOF(RTVFSFILEOPS, ObjSet) - RT_UOFFSETOF(RTVFSFILEOPS, Stream.Obj), vdVfsFile_SetMode, vdVfsFile_SetTimes, vdVfsFile_SetOwner, RTVFSOBJSETOPS_VERSION }, vdVfsFile_Seek, vdVfsFile_QuerySize, NULL /*SetSize*/, NULL /*QueryMaxSize*/, RTVFSFILEOPS_VERSION }; VBOXDDU_DECL(int) VDCreateVfsFileFromDisk(PVDISK pDisk, uint32_t fFlags, PRTVFSFILE phVfsFile) { AssertPtrReturn(pDisk, VERR_INVALID_HANDLE); AssertPtrReturn(phVfsFile, VERR_INVALID_POINTER); AssertReturn((fFlags & ~VD_VFSFILE_FLAGS_MASK) == 0, VERR_INVALID_PARAMETER); /* * Create the volume file. */ RTVFSFILE hVfsFile; PVDVFSFILE pThis; int rc = RTVfsNewFile(&g_vdVfsStdFileOps, sizeof(*pThis), RTFILE_O_OPEN | RTFILE_O_READ | RTFILE_O_WRITE, NIL_RTVFS, NIL_RTVFSLOCK, &hVfsFile, (void **)&pThis); if (RT_SUCCESS(rc)) { pThis->offCurPos = 0; pThis->pDisk = pDisk; pThis->fFlags = fFlags; *phVfsFile = hVfsFile; return VINF_SUCCESS; } return rc; } /** * @interface_method_impl{RTVFSCHAINELEMENTREG,pfnValidate} */ static DECLCALLBACK(int) vdVfsChain_Validate(PCRTVFSCHAINELEMENTREG pProviderReg, PRTVFSCHAINSPEC pSpec, PRTVFSCHAINELEMSPEC pElement, uint32_t *poffError, PRTERRINFO pErrInfo) { RT_NOREF(pProviderReg, pSpec); /* * Basic checks. */ if (pElement->enmTypeIn != RTVFSOBJTYPE_INVALID) return VERR_VFS_CHAIN_MUST_BE_FIRST_ELEMENT; if ( pElement->enmType != RTVFSOBJTYPE_FILE && pElement->enmType != RTVFSOBJTYPE_IO_STREAM) return VERR_VFS_CHAIN_ONLY_FILE_OR_IOS; if (pElement->cArgs < 1) return VERR_VFS_CHAIN_AT_LEAST_ONE_ARG; /* * Parse the flag if present, save in pElement->uProvider. */ uint32_t fFlags = (pSpec->fOpenFile & RTFILE_O_ACCESS_MASK) == RTFILE_O_READ ? VD_OPEN_FLAGS_READONLY : VD_OPEN_FLAGS_NORMAL; if (pElement->cArgs > 1) { pElement->paArgs[pElement->cArgs - 1].uProvider = true; /* indicates flags */ const char *psz = pElement->paArgs[pElement->cArgs - 1].psz; if (*psz) { if ( !strcmp(psz, "ro") || !strcmp(psz, "r")) { fFlags &= ~(VD_OPEN_FLAGS_READONLY | VD_OPEN_FLAGS_NORMAL); fFlags |= VD_OPEN_FLAGS_READONLY; } else if (!strcmp(psz, "rw")) { fFlags &= ~(VD_OPEN_FLAGS_READONLY | VD_OPEN_FLAGS_NORMAL); fFlags |= VD_OPEN_FLAGS_NORMAL; } else if (strlen(psz) <= 4) { *poffError = pElement->paArgs[pElement->cArgs - 1].offSpec; return RTErrInfoSet(pErrInfo, VERR_VFS_CHAIN_INVALID_ARGUMENT, "Expected 'ro' or 'rw' as argument"); } else pElement->paArgs[pElement->cArgs - 1].uProvider = false; /* indicates no flags */ } } pElement->uProvider = fFlags; if ( pElement->cArgs > 2 || (pElement->cArgs == 2 && !pElement->paArgs[pElement->cArgs - 1].uProvider)) pElement->uProvider |= RT_BIT_64(63); return VINF_SUCCESS; } /** * @interface_method_impl{RTVFSCHAINELEMENTREG,pfnInstantiate} */ static DECLCALLBACK(int) vdVfsChain_Instantiate(PCRTVFSCHAINELEMENTREG pProviderReg, PCRTVFSCHAINSPEC pSpec, PCRTVFSCHAINELEMSPEC pElement, RTVFSOBJ hPrevVfsObj, PRTVFSOBJ phVfsObj, uint32_t *poffError, PRTERRINFO pErrInfo) { RT_NOREF(pProviderReg, pSpec, poffError, pErrInfo); AssertReturn(hPrevVfsObj == NIL_RTVFSOBJ, VERR_VFS_CHAIN_IPE); /* Determin the format. */ char *pszFormat = NULL; VDTYPE enmType = VDTYPE_INVALID; int rc = VDGetFormat(NULL, NULL, pElement->paArgs[0].psz, VDTYPE_INVALID, &pszFormat, &enmType); if (RT_SUCCESS(rc)) { PVDISK pDisk = NULL; rc = VDCreate(NULL, enmType, &pDisk); if (RT_SUCCESS(rc)) { if (!(pElement->uProvider & RT_BIT_64(63))) rc = VDOpen(pDisk, pszFormat, pElement->paArgs[0].psz, (uint32_t)pElement->uProvider, NULL); else { uint32_t cChain = pElement->cArgs; if (pElement->cArgs >= 2 && pElement->paArgs[pElement->cArgs - 1].uProvider != 0) cChain--; uint32_t const fFinal = (uint32_t)pElement->uProvider; uint32_t const fReadOnly = (fFinal & ~(VD_OPEN_FLAGS_READONLY | VD_OPEN_FLAGS_NORMAL)) | VD_OPEN_FLAGS_READONLY; uint32_t iChain; for (iChain = 0; iChain < cChain && RT_SUCCESS(rc); iChain++) rc = VDOpen(pDisk, pszFormat, pElement->paArgs[iChain].psz, iChain + 1 >= cChain ? fFinal : fReadOnly, NULL); } if (RT_SUCCESS(rc)) { RTVFSFILE hVfsFile; rc = VDCreateVfsFileFromDisk(pDisk, VD_VFSFILE_DESTROY_ON_RELEASE, &hVfsFile); if (RT_SUCCESS(rc)) { RTStrFree(pszFormat); *phVfsObj = RTVfsObjFromFile(hVfsFile); RTVfsFileRelease(hVfsFile); if (*phVfsObj != NIL_RTVFSOBJ) return VINF_SUCCESS; return VERR_VFS_CHAIN_CAST_FAILED; } } VDDestroy(pDisk); } RTStrFree(pszFormat); } return rc; } /** * @interface_method_impl{RTVFSCHAINELEMENTREG,pfnCanReuseElement} */ static DECLCALLBACK(bool) vdVfsChain_CanReuseElement(PCRTVFSCHAINELEMENTREG pProviderReg, PCRTVFSCHAINSPEC pSpec, PCRTVFSCHAINELEMSPEC pElement, PCRTVFSCHAINSPEC pReuseSpec, PCRTVFSCHAINELEMSPEC pReuseElement) { RT_NOREF(pProviderReg, pSpec, pElement, pReuseSpec, pReuseElement); return false; } /** VFS chain element 'file'. */ static RTVFSCHAINELEMENTREG g_rtVfsChainIsoFsVolReg = { /* uVersion = */ RTVFSCHAINELEMENTREG_VERSION, /* fReserved = */ 0, /* pszName = */ "vd", /* ListEntry = */ { NULL, NULL }, /* pszHelp = */ "Opens a container image using the VD API.\n" "To open a snapshot chain, start with the root image and end with the more recent diff image.\n" "The final argument can be a flag 'ro' or 'r' for read-only, 'rw' for read-write.", /* pfnValidate = */ vdVfsChain_Validate, /* pfnInstantiate = */ vdVfsChain_Instantiate, /* pfnCanReuseElement = */ vdVfsChain_CanReuseElement, /* uEndMarker = */ RTVFSCHAINELEMENTREG_VERSION }; RTVFSCHAIN_AUTO_REGISTER_ELEMENT_PROVIDER(&g_rtVfsChainIsoFsVolReg, rtVfsChainIsoFsVolReg);