Index SLRUs by 64-bit integers rather than by 32-bit integers

We've had repeated bugs in the area of handling SLRU wraparound in the past,
some of which have caused data loss. Switching to an indexing system for SLRUs
that does not wrap around should allow us to get rid of a whole bunch
of problems and improve the overall reliability of the system.

This particular patch however only changes the indexing and doesn't address
the wraparound per se. This is going to be done in the following patches.

Author: Maxim Orlov, Aleksander Alekseev, Alexander Korotkov, Teodor Sigaev
Author: Nikita Glukhov, Pavel Borisov, Yura Sokolov
Reviewed-by: Jacob Champion, Heikki Linnakangas, Alexander Korotkov
Reviewed-by: Japin Li, Pavel Borisov, Tom Lane, Peter Eisentraut, Andres Freund
Reviewed-by: Andrey Borodin, Dilip Kumar, Aleksander Alekseev
Discussion: https://postgr.es/m/CACG%3DezZe1NQSCnfHOr78AtAZxJZeCvxrts0ygrxYwe%3DpyyjVWA%40mail.gmail.com
Discussion: https://postgr.es/m/CAJ7c6TPDOYBYrnCAeyndkBktO0WG2xSdYduTF0nxq%2BvfkmTF5Q%40mail.gmail.com

1 files changed, 10 insertions, 10 deletions

diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
index 38ddae08b86..346bc28a36f 100644
--- a/src/backend/commands/async.c
+++ b/src/backend/commands/async.c
@@ -196,7 +196,7 @@ typedef struct AsyncQueueEntry
  */
 typedef struct QueuePosition
 {
-	int			page;			/* SLRU page number */
+	int64		page;			/* SLRU page number */
 	int			offset;			/* byte offset within page */
 } QueuePosition;
 
@@ -443,8 +443,8 @@ static bool tryAdvanceTail = false;
 bool		Trace_notify = false;
 
 /* local function prototypes */
-static int	asyncQueuePageDiff(int p, int q);
-static bool asyncQueuePagePrecedes(int p, int q);
+static int64 asyncQueuePageDiff(int64 p, int64 q);
+static bool asyncQueuePagePrecedes(int64 p, int64 q);
 static void queue_listen(ListenActionKind action, const char *channel);
 static void Async_UnlistenOnExit(int code, Datum arg);
 static void Exec_ListenPreCommit(void);
@@ -477,10 +477,10 @@ static void ClearPendingActionsAndNotifies(void);
  * Compute the difference between two queue page numbers (i.e., p - q),
  * accounting for wraparound.
  */
-static int
-asyncQueuePageDiff(int p, int q)
+static int64
+asyncQueuePageDiff(int64 p, int64 q)
 {
-	int			diff;
+	int64		diff;
 
 	/*
 	 * We have to compare modulo (QUEUE_MAX_PAGE+1)/2.  Both inputs should be
@@ -504,7 +504,7 @@ asyncQueuePageDiff(int p, int q)
  * extant page, we need not assess entries within a page.
  */
 static bool
-asyncQueuePagePrecedes(int p, int q)
+asyncQueuePagePrecedes(int64 p, int64 q)
 {
 	return asyncQueuePageDiff(p, q) < 0;
 }
@@ -571,7 +571,7 @@ AsyncShmemInit(void)
 	NotifyCtl->PagePrecedes = asyncQueuePagePrecedes;
 	SimpleLruInit(NotifyCtl, "Notify", NUM_NOTIFY_BUFFERS, 0,
 				  NotifySLRULock, "pg_notify", LWTRANCHE_NOTIFY_BUFFER,
-				  SYNC_HANDLER_NONE);
+				  SYNC_HANDLER_NONE, false);
 
 	if (!found)
 	{
@@ -1336,7 +1336,7 @@ asyncQueueIsFull(void)
 static bool
 asyncQueueAdvance(volatile QueuePosition *position, int entryLength)
 {
-	int			pageno = QUEUE_POS_PAGE(*position);
+	int64		pageno = QUEUE_POS_PAGE(*position);
 	int			offset = QUEUE_POS_OFFSET(*position);
 	bool		pageJump = false;
 
@@ -1409,7 +1409,7 @@ asyncQueueAddEntries(ListCell *nextNotify)
 {
 	AsyncQueueEntry qe;
 	QueuePosition queue_head;
-	int			pageno;
+	int64		pageno;
 	int			offset;
 	int			slotno;