Convert the arithmetic for shared memory size calculation from 'int'

to 'Size' (that is, size_t), and install overflow detection checks in it.
This allows us to remove the former arbitrary restrictions on NBuffers
etc.  It won't make any difference in a 32-bit machine, but in a 64-bit
machine you could theoretically have terabytes of shared buffers.
(How efficiently we could manage 'em remains to be seen.)  Similarly,
num_temp_buffers, work_mem, and maintenance_work_mem can be set above
2Gb on a 64-bit machine.  Original patch from Koichi Suzuki, additional
work by moi.

src/backend/access/transam/clog.c

@@ -24,7 +24,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.31 2005/06/30 00:00:50 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.32 2005/08/20 23:26:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -144,8 +144,7 @@ TransactionIdGetStatus(TransactionId xid)
 /*
  * Initialization of shared memory for CLOG
  */
-
-int
+Size
 CLOGShmemSize(void)
 {
 	return SimpleLruShmemSize();

src/backend/access/transam/multixact.c

@@ -42,7 +42,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/multixact.c,v 1.7 2005/08/20 01:29:27 ishii Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/multixact.c,v 1.8 2005/08/20 23:26:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1159,13 +1159,20 @@ AtEOXact_MultiXact(void)
  * thus double memory.  Also, reserve space for the shared MultiXactState
  * struct and the per-backend MultiXactId arrays (two of those, too).
  */
-int
+Size
 MultiXactShmemSize(void)
 {
-#define SHARED_MULTIXACT_STATE_SIZE \
-	(sizeof(MultiXactStateData) + sizeof(MultiXactId) * 2 * MaxBackends)
+	Size		size;
 
-	return (SimpleLruShmemSize() * 2 + SHARED_MULTIXACT_STATE_SIZE);
+#define SHARED_MULTIXACT_STATE_SIZE \
+	add_size(sizeof(MultiXactStateData), \
+			 mul_size(sizeof(MultiXactId) * 2, MaxBackends))
+
+	size = SHARED_MULTIXACT_STATE_SIZE;
+	size = add_size(size, SimpleLruShmemSize());
+	size = add_size(size, SimpleLruShmemSize());
+
+	return size;
 }
 
 void

src/backend/access/transam/slru.c

@@ -48,7 +48,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/slru.c,v 1.26 2005/07/04 04:51:44 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/slru.c,v 1.27 2005/08/20 23:26:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -141,9 +141,10 @@ static int	SlruSelectLRUPage(SlruCtl ctl, int pageno);
  * Initialization of shared memory
  */
 
-int
+Size
 SimpleLruShmemSize(void)
 {
+	/* we assume NUM_SLRU_BUFFERS isn't so large as to risk overflow */
 	return BUFFERALIGN(sizeof(SlruSharedData)) + BLCKSZ * NUM_SLRU_BUFFERS;
 }
 

src/backend/access/transam/subtrans.c

@@ -22,7 +22,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/subtrans.c,v 1.9 2005/06/17 22:32:42 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/subtrans.c,v 1.10 2005/08/20 23:26:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -161,8 +161,7 @@ SubTransGetTopmostTransaction(TransactionId xid)
 /*
  * Initialization of shared memory for SUBTRANS
  */
-
-int
+Size
 SUBTRANSShmemSize(void)
 {
 	return SimpleLruShmemSize();

src/backend/access/transam/twophase.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *		$PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.9 2005/07/31 17:19:17 tgl Exp $
+ *		$PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.10 2005/08/20 23:26:10 tgl Exp $
  *
  * NOTES
  *		Each global transaction is associated with a global transaction
@@ -152,13 +152,20 @@ static void ProcessRecords(char *bufptr, TransactionId xid,
 /*
  * Initialization of shared memory
  */
-int
+Size
 TwoPhaseShmemSize(void)
 {
+	Size		size;
+
 	/* Need the fixed struct, the array of pointers, and the GTD structs */
-	return MAXALIGN(offsetof(TwoPhaseStateData, prepXacts) + 
-					sizeof(GlobalTransaction) * max_prepared_xacts) +
-		sizeof(GlobalTransactionData) * max_prepared_xacts;
+	size = offsetof(TwoPhaseStateData, prepXacts);
+	size = add_size(size, mul_size(max_prepared_xacts,
+								   sizeof(GlobalTransaction)));
+	size = MAXALIGN(size);
+	size = add_size(size, mul_size(max_prepared_xacts,
+								   sizeof(GlobalTransactionData)));
+
+	return size;
 }
 
 void

src/backend/access/transam/xlog.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.215 2005/08/11 21:11:43 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.216 2005/08/20 23:26:10 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -91,31 +91,6 @@
 #endif
 #endif
 
-/*
- * Limitation of buffer-alignment for direct io depend on OS and filesystem,
- * but BLCKSZ is assumed to be enough for it. 
- */
-#ifdef O_DIRECT
-#define ALIGNOF_XLOG_BUFFER		BLCKSZ
-#else
-#define ALIGNOF_XLOG_BUFFER		MAXIMUM_ALIGNOF
-#endif
-
-/*
- * Switch the alignment routine because ShmemAlloc() returns a max-aligned
- * buffer and ALIGNOF_XLOG_BUFFER may be greater than MAXIMUM_ALIGNOF.
- */
-#if ALIGNOF_XLOG_BUFFER <= MAXIMUM_ALIGNOF
-#define XLOG_BUFFER_ALIGN(LEN)	MAXALIGN((LEN))
-#else
-#define XLOG_BUFFER_ALIGN(LEN)	((LEN) + (ALIGNOF_XLOG_BUFFER))
-#endif
-/* assume sizeof(ptrdiff_t) == sizeof(void*) */
-#define POINTERALIGN(ALIGNVAL,PTR)	\
-	((char *)(((ptrdiff_t) (PTR) + (ALIGNVAL-1)) & ~((ptrdiff_t) (ALIGNVAL-1))))
-#define XLOG_BUFFER_POINTERALIGN(PTR)	\
-	POINTERALIGN((ALIGNOF_XLOG_BUFFER), (PTR))
-
 #ifdef OPEN_DATASYNC_FLAG
 #define DEFAULT_SYNC_METHOD_STR	"open_datasync"
 #define DEFAULT_SYNC_METHOD		SYNC_METHOD_OPEN
@@ -135,6 +110,17 @@
 #endif
 
 
+/*
+ * Limitation of buffer-alignment for direct IO depends on OS and filesystem,
+ * but BLCKSZ is assumed to be enough for it. 
+ */
+#ifdef O_DIRECT
+#define ALIGNOF_XLOG_BUFFER		BLCKSZ
+#else
+#define ALIGNOF_XLOG_BUFFER		ALIGNOF_BUFFER
+#endif
+
+
 /* File path names (all relative to $PGDATA) */
 #define BACKUP_LABEL_FILE		"backup_label"
 #define RECOVERY_COMMAND_FILE	"recovery.conf"
@@ -173,8 +159,6 @@ static int	open_sync_bit = DEFAULT_SYNC_FLAGBIT;
 
 #define XLOG_SYNC_BIT  (enableFsync ? open_sync_bit : 0)
 
-#define MinXLOGbuffers	4
-
 
 /*
  * ThisTimeLineID will be same in all backends --- it identifies current
@@ -3615,16 +3599,27 @@ UpdateControlFile(void)
 /*
  * Initialization of shared memory for XLOG
  */
-
-int
+Size
 XLOGShmemSize(void)
 {
-	if (XLOGbuffers < MinXLOGbuffers)
-		XLOGbuffers = MinXLOGbuffers;
+	Size		size;
 
-	return XLOG_BUFFER_ALIGN(sizeof(XLogCtlData) + sizeof(XLogRecPtr) * XLOGbuffers)
-		+ BLCKSZ * XLOGbuffers +
-		MAXALIGN(sizeof(ControlFileData));
+	/* XLogCtl */
+	size = sizeof(XLogCtlData);
+	/* xlblocks array */
+	size = add_size(size, mul_size(sizeof(XLogRecPtr), XLOGbuffers));
+	/* extra alignment padding for XLOG I/O buffers */
+	size = add_size(size, ALIGNOF_XLOG_BUFFER);
+	/* and the buffers themselves */
+	size = add_size(size, mul_size(BLCKSZ, XLOGbuffers));
+
+	/*
+	 * Note: we don't count ControlFileData, it comes out of the "slop
+	 * factor" added by CreateSharedMemoryAndSemaphores.  This lets us
+	 * use this routine again below to compute the actual allocation size.
+	 */
+
+	return size;
 }
 
 void
@@ -3632,17 +3627,10 @@ XLOGShmemInit(void)
 {
 	bool		foundXLog,
 				foundCFile;
-
-	/* this must agree with space requested by XLOGShmemSize() */
-	if (XLOGbuffers < MinXLOGbuffers)
-		XLOGbuffers = MinXLOGbuffers;
+	char	   *allocptr;
 
 	XLogCtl = (XLogCtlData *)
-		ShmemInitStruct("XLOG Ctl",
-						XLOG_BUFFER_ALIGN(sizeof(XLogCtlData) +
-								 sizeof(XLogRecPtr) * XLOGbuffers)
-						+ BLCKSZ * XLOGbuffers,
-						&foundXLog);
+		ShmemInitStruct("XLOG Ctl", XLOGShmemSize(), &foundXLog);
 	ControlFile = (ControlFileData *)
 		ShmemInitStruct("Control File", sizeof(ControlFileData), &foundCFile);
 
@@ -3660,17 +3648,16 @@ XLOGShmemInit(void)
 	 * a multiple of the alignment for same, so no extra alignment padding
 	 * is needed here.
 	 */
-	XLogCtl->xlblocks = (XLogRecPtr *)
-		(((char *) XLogCtl) + sizeof(XLogCtlData));
+	allocptr = ((char *) XLogCtl) + sizeof(XLogCtlData);
+	XLogCtl->xlblocks = (XLogRecPtr *) allocptr;
 	memset(XLogCtl->xlblocks, 0, sizeof(XLogRecPtr) * XLOGbuffers);
+	allocptr += sizeof(XLogRecPtr) * XLOGbuffers;
 
 	/*
-	 * Here, on the other hand, we must MAXALIGN to ensure the page
-	 * buffers have worst-case alignment.
+	 * Align the start of the page buffers to an ALIGNOF_XLOG_BUFFER boundary.
 	 */
-	XLogCtl->pages = XLOG_BUFFER_POINTERALIGN(
-		((char *) XLogCtl)
-		+ sizeof(XLogCtlData) + sizeof(XLogRecPtr) * XLOGbuffers);
+	allocptr = (char *) TYPEALIGN(ALIGNOF_XLOG_BUFFER, allocptr);
+	XLogCtl->pages = allocptr;
 	memset(XLogCtl->pages, 0, BLCKSZ * XLOGbuffers);
 
 	/*
@@ -3728,8 +3715,9 @@ BootStrapXLOG(void)
 	/* First timeline ID is always 1 */
 	ThisTimeLineID = 1;
 
- 	buffer = (char *) malloc(BLCKSZ + ALIGNOF_XLOG_BUFFER);
-	page = (XLogPageHeader) XLOG_BUFFER_POINTERALIGN(buffer);
+	/* page buffer must be aligned suitably for O_DIRECT */
+ 	buffer = (char *) palloc(BLCKSZ + ALIGNOF_XLOG_BUFFER);
+	page = (XLogPageHeader) TYPEALIGN(ALIGNOF_XLOG_BUFFER, buffer);
 	memset(page, 0, BLCKSZ);
 
 	/* Set up information for the initial checkpoint record */
@@ -3824,7 +3812,7 @@ BootStrapXLOG(void)
 	BootStrapSUBTRANS();
 	BootStrapMultiXact();
 
-	free(buffer);
+	pfree(buffer);
 }
 
 static char *