[ros-kernel] Re: Kernel Bug

[Guido de J. <gui...@ch...>]

Now I don't too much about ReactOS programming, but IMHO Jack was quite plain 
about it:

There is this function called MiReadPage() which you can find in 
mm/section.c, lines 252-337. This function does a call to IOReadPage() in 
line 290, if the page in cache is not up-to-date. According to Jack it is not 
an error if this function returns STATUS_END_OF_FILE, which apparently is not 
equal to NT_SUCCESS(). So he added

	&& Status != STATUS_END_OF_FILE

to line 295. IMHO it will have been even better if you add

	&& (Status != STATUS_END_OF_FILE)

in stead. Do you really need a diff for this?

See added line numbers below.

- Guido


On Tuesday 25 September 2001 20:27, Jason Filby wrote:
> Has anyone tested/updated the tree with this update and the latest
> one from Jack?
>
> Jack: it seems that most developers prefer that you send them the
> "diffs".. but I don't think I have diff installed?..
>
> - Jason
>
> --- "Jack (Butch) Griffin" <bu...@qw...> wrote:
> > I have been playing with the ReactOS operating system and trying to
> > get a
> > console mode app written in vistual C++ to run.  The app is your
> > basic hello
> > world application.  I did not really expect that the complete
> > infra-structure was in place for this to run, but I figured it
> > would point
> > out what was missing and give me a starting point for beginning to
> > learn
> > about the design of this OS.
> >
> > Anyway I have found a problem and do not know who should get the
> > updated
> > code.  The problem is in MiReadPage() and the updated code is
> > below.  The
> > only change is that STATUS_END_OF_FILE is a legimate return from
> > IoPageRead().  It does not mean an error occurred, just that the
> > file did
> > not contain enough data to fill the page.  Function that call
> > MiReadPage()
> > assume that the data read are OK if the return value is
> > STATUS_END_OF_FILE,
> > so the update of the Page pointer must be done in this case.
> >
> > Thanks
> > Jack Griffin

252: NTSTATUS
MiReadPage(PMEMORY_AREA MemoryArea,
	   PLARGE_INTEGER Offset,
	   PVOID* Page)
{
  IO_STATUS_BLOCK IoStatus;
  PFILE_OBJECT FileObject;
  PMDL Mdl;
  NTSTATUS Status;
  PREACTOS_COMMON_FCB_HEADER Fcb;

  FileObject = MemoryArea->Data.SectionData.Section->FileObject;
  Fcb = (PREACTOS_COMMON_FCB_HEADER)FileObject->FsContext;

  if (FileObject->Flags & FO_DIRECT_CACHE_PAGING_READ &&
      (Offset->QuadPart % PAGESIZE) == 0)
    {
      ULONG BaseOffset;
      PVOID BaseAddress;
      BOOLEAN UptoDate;
      PCACHE_SEGMENT CacheSeg;
      LARGE_INTEGER SegOffset;
      PHYSICAL_ADDRESS Addr;
      Status = CcRosGetCacheSegment(Fcb->Bcb,
				 (ULONG)Offset->QuadPart,
				 &BaseOffset,
				 &BaseAddress,
				 &UptoDate,
				 &CacheSeg);
      if (!NT_SUCCESS(Status))
	{
	  return(Status);
	}
      if (!UptoDate)
	{
	  Mdl = MmCreateMdl(NULL, BaseAddress, Fcb->Bcb->CacheSegmentSize);
	  MmBuildMdlForNonPagedPool(Mdl);
	  SegOffset.QuadPart = BaseOffset;
290:	  Status = IoPageRead(FileObject,
			      Mdl,
			      &SegOffset,
			      &IoStatus,
			      TRUE);
295:	  if (!NT_SUCCESS(Status) && Status != STATUS_END_OF_FILE)
	    {
	      CcRosReleaseCacheSegment(Fcb->Bcb, CacheSeg, FALSE);
	      return(Status);
	    }
	}
      Addr = MmGetPhysicalAddress(BaseAddress +
				  Offset->QuadPart - BaseOffset);
      (*Page) = (PVOID)(ULONG)Addr.QuadPart;
      MmReferencePage((*Page));

      CcRosReleaseCacheSegment(Fcb->Bcb, CacheSeg, TRUE);
      return(STATUS_SUCCESS);
    }
  else
    {
      /*
       * Allocate a page, this is rather complicated by the possibility
       * we might have to move other things out of memory
       */
      (*Page) = MmAllocPage(0);
      while ((*Page) == NULL)
	{
	  MmWaitForFreePages();
	  (*Page) = MmAllocPage(0);
	}

      /*
       * Create an mdl to hold the page we are going to read data into.
       */
      Mdl = MmCreateMdl(NULL, NULL, PAGESIZE);
      MmBuildMdlFromPages(Mdl, (PULONG)Page);
      /*
       * Call the FSD to read the page
       */
      Status = IoPageRead(FileObject,
			  Mdl,
			  Offset,
			  &IoStatus,
			  FALSE);
      return(Status);
    }
337: }

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