[ros-kernel] AW: Re: AW: Re: AW: Re: Cache and memory manager

[Hartmut B. <har...@te...>]

> -----Ursprungliche Nachricht-----
> Von:	David Welch [SMTP:we...@cw...]
> Gesendet am:	Dienstag, 23. Oktober 2001 23:56
> An:	ros...@re...
> Betreff:	[ros-kernel] Re: AW: Re: AW: Re: Cache and memory manager
> 
> Okay, for reference what are the bugs exactly?

MiAllocPageFromPagingFile() returns for each reserved page 
the entry 1 and the calculation of the used and free pages is wrong.
See also the comments in the diff output (marked with '-->'). 

- Hartmut

Index: pagefile.c
===================================================================
RCS file: /CVS/ReactOS/reactos/ntoskrnl/mm/pagefile.c,v
retrieving revision 1.12
diff -u -r1.12 pagefile.c
--- pagefile.c	2001/10/10 21:57:00	1.12
+++ pagefile.c	2001/10/24 17:21:56
@@ -97,7 +97,7 @@
  */
 #define FILE_FROM_ENTRY(i) ((i) >> 24)
 #define OFFSET_FROM_ENTRY(i) (((i) & 0xffffff) - 1)
-#define ENTRY_FROM_FILE_OFFSET(i, j) (((i) << 24) || ((j) + 1))
+#define ENTRY_FROM_FILE_OFFSET(i, j) (((i) << 24) | ((j) + 1))
 
 /* FUNCTIONS *****************************************************************/
 
@@ -123,7 +123,7 @@
 			Mdl,
 			&file_offset,
 			&Iosb,
-			FALSE);
+			TRUE);
    return(Status);
 }
 
@@ -204,24 +204,23 @@
 MiAllocPageFromPagingFile(PPAGINGFILE PagingFile)
 {
    KIRQL oldIrql;
-   ULONG i;
    ULONG off;
    
    KeAcquireSpinLock(&PagingFile->AllocMapLock, &oldIrql);
    
-   for (i = 0; i < PagingFile->AllocMapSize; i++)
-     {
-	off = find_first_zero_bit(PagingFile->AllocMap, 
-				  PagingFile->AllocMapSize * 32);
-	clear_bit(off % 32, &PagingFile->AllocMap[off / 32]);		--> The bit must be set.
-	PagingFile->UsedPages--;					--> Must be increment.
-	PagingFile->FreePages++;					--> Must be decrement.
+   off = find_first_zero_bit(PagingFile->AllocMap, 
+			     PagingFile->AllocMapSize * 32);
+   if (off < PagingFile->CurrentSize)					--> Check for a valid offset.
+   {
+	set_bit(off % 32, &PagingFile->AllocMap[off / 32]);
+	PagingFile->UsedPages++;
+	PagingFile->FreePages--;
 	KeReleaseSpinLock(&PagingFile->AllocMapLock, oldIrql);
 	return(off);
-     }
+   }
    
    KeReleaseSpinLock(&PagingFile->AllocMapLock, oldIrql);
-   return(0);
+   return(0xffffffff);							--> Return a nonvalid entry.
 }
 
 VOID 
@@ -237,7 +236,7 @@
    KeAcquireSpinLock(&PagingFileListLock, &oldIrql);
    KeAcquireSpinLockAtDpcLevel(&PagingFileList[i]->AllocMapLock);
    
-   set_bit(off % 32, &PagingFileList[i]->AllocMap[off / 32]);		--> Bit must be reset.
+   clear_bit(off % 32, &PagingFileList[i]->AllocMap[off / 32]);
    
    PagingFileList[i]->FreePages++;
    PagingFileList[i]->UsedPages--;
@@ -271,11 +270,10 @@
 	    PagingFileList[i]->FreePages >= 1)
 	  {	     
 	     off = MiAllocPageFromPagingFile(PagingFileList[i]);
-	     if (off != 0)
+	     if (off == 0xffffffff)						--> Check vor invalid value.
 	       {
+		  DPRINT1("MiAllocPageFromPagingFile() doesn't return a free page, but FreeCount is %d\n", PagingFileList[i]->FreePages);
 		  KeBugCheck(0);
-		  KeReleaseSpinLock(&PagingFileListLock, oldIrql);	--> Has no effect after KeBugCheck().
-		  return(STATUS_UNSUCCESSFUL);
 	       }
 	     MiUsedSwapPages++;
 	     MiFreeSwapPages--;

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