Re: [ros-dev] [ros-diffs] [tthompson] 71968: [NTFS] +FreeClusters(). Fix a DPRINT.

[Pierre Schweitzer]

Comment inline.

Le 19/07/2016 à 17:31, tthompson(a)svn.reactos.org a écrit :
>   Author: tthompson
>  Date: Tue Jul 19 15:31:22 2016
>  New Revision: 71968
>  
>  URL: http://svn.reactos.org/svn/reactos?rev=71968&view=rev
>  Log:
>  [NTFS]
>  +FreeClusters(). Fix a DPRINT.
>  
>  Modified:
>      branches/GSoC_2016/NTFS/drivers/filesystems/ntfs/attrib.c
>      branches/GSoC_2016/NTFS/drivers/filesystems/ntfs/mft.c
>      branches/GSoC_2016/NTFS/drivers/filesystems/ntfs/ntfs.h
>  
>  Modified: branches/GSoC_2016/NTFS/drivers/filesystems/ntfs/attrib.c
>  URL:
> http://svn.reactos.org/svn/reactos/branches/GSoC_2016/NTFS/drivers/filesyst…
>  ==============================================================================
>  --- branches/GSoC_2016/NTFS/drivers/filesystems/ntfs/attrib.c	[iso-8859-1] (original)
>  +++ branches/GSoC_2016/NTFS/drivers/filesystems/ntfs/attrib.c	[iso-8859-1] Tue Jul 19
> 15:31:22 2016
>  @@ -409,6 +409,208 @@
>       return TRUE;
>   }
>   
>  +/**
>  +* @name FreeClusters
>  +* @implemented
>  +*
>  +* Shrinks the allocation size of a non-resident attribute by a given number of
> clusters.
>  +* Frees the clusters from the volume's $BITMAP file as well as the attribute's
> data runs.
>  +*
>  +* @param Vcb
>  +* Pointer to an NTFS_VCB for the destination volume.
>  +*
>  +* @param AttrContext
>  +* Pointer to an NTFS_ATTR_CONTEXT describing the attribute from which the clusters will
> be freed.
>  +*
>  +* @param AttrOffset
>  +* Byte offset of the destination attribute relative to its file record.
>  +*
>  +* @param FileRecord
>  +* Pointer to a complete copy of the file record containing the attribute. Must be at
> least
>  +* Vcb->NtfsInfo.BytesPerFileRecord bytes long.
>  +*
>  +* @param ClustersToFree
>  +* Number of clusters that should be freed from the end of the data stream. Must be no
> more
>  +* Than the number of clusters assigned to the attribute (HighestVCN + 1).
>  +*
>  +* @return
>  +* STATUS_SUCCESS on success. STATUS_INVALID_PARAMETER if AttrContext describes a
> resident attribute,
>  +* or if the caller requested more clusters be freed than the attribute has been
> allocated.
>  +* STATUS_INSUFFICIENT_RESOURCES if ConvertDataRunsToLargeMCB() fails.
>  +* STATUS_BUFFER_TOO_SMALL if ConvertLargeMCBToDataRuns() fails.
>  +*
>  +*
>  +*/
>  +NTSTATUS
>  +FreeClusters(PNTFS_VCB Vcb,
>  +             PNTFS_ATTR_CONTEXT AttrContext,
>  +             ULONG AttrOffset,
>  +             PFILE_RECORD_HEADER FileRecord,
>  +             ULONG ClustersToFree)
>  +{
>  +    NTSTATUS Status = STATUS_SUCCESS;
>  +    ULONG ClustersLeftToFree = ClustersToFree;
>  +
>  +    // convert data runs to mcb
>  +    PUCHAR DataRun = (PUCHAR)&AttrContext->Record +
> AttrContext->Record.NonResident.MappingPairsOffset;
>  +    PNTFS_ATTR_RECORD DestinationAttribute = (PNTFS_ATTR_RECORD)((ULONG_PTR)FileRecord +
> AttrOffset);
>  +    LARGE_MCB DataRunsMCB;
>  +    ULONG NextAttributeOffset = AttrOffset + AttrContext->Record.Length;
>  +    PNTFS_ATTR_RECORD NextAttribute = (PNTFS_ATTR_RECORD)((ULONG_PTR)FileRecord +
> NextAttributeOffset);
>  +    ULONGLONG NextVBN = AttrContext->Record.NonResident.LowestVCN;
>  +
>  +    // Allocate some memory for the RunBuffer
>  +    PUCHAR RunBuffer = ExAllocatePoolWithTag(NonPagedPool,
> Vcb->NtfsInfo.BytesPerFileRecord, TAG_NTFS);
>  +    ULONG RunBufferOffset = 0; 
Two notes regarding this allocation:
- You should check allocation worked (obviously ;-));
- You should start memory work only after checking the record is not
resident.

-- 
Pierre Schweitzer <pierre at reactos.org>
System & Network Administrator
Senior Kernel Developer
ReactOS Deutschland e.V.