Re: XID formatting and SLRU refactorings (was: Add 64-bit XIDs into PostgreSQL 15)

+SlruScanDirCbFindEarliest(SlruCtl ctl, char *filename, int64 segpage, void *data)
segpage doesn't fit mxtruncinfo.earliestExistingPage. Doesn't it need
to be int64?

+ return snprintf(path, MAXPGPATH, "%s/%04llX", ctl->Dir, (long long) segno);  

We have two way to go here. One way is expanding the file name
according to the widened segno, another is keep the old format string
then cast the segno to (int). Since the objective of this patch is
widen pageno, I think, as Pavel's comment upthread, we should widen
the file format to "%s/%012llX".

As Peter suggested upthread,
+ int64 segno = pageno / SLRU_PAGES_PER_SEGMENT;
+ int64 rpageno = pageno % SLRU_PAGES_PER_SEGMENT;
+ int64 offset = rpageno * BLCKSZ;
rpageno is apparently over-sized. So offset is also over-sized. segno
can be up to 48 bits (maybe) so int64 is appropriate.

-SlruPhysicalWritePage(SlruCtl ctl, int pageno, int slotno, SlruWriteAll fdata)
+SlruPhysicalWritePage(SlruCtl ctl, int64 pageno, int slotno, SlruWriteAll fdata)
This function does the followng.
> FileTag tag;
>
> INIT_SLRUFILETAG(tag, ctl->sync_handler, segno);
tag.segno is uin32, which is too narrow here.

This is not an issue of this patch, but..
- errdetail("Could not read from file \"%s\" at offset %u: %m.",
- path, offset)));
Why do we print int by "%u" here, even though that doesn't harm at all?

-SlruScanDirCbReportPresence(SlruCtl ctl, char *filename, int segpage, void *data)
+SlruScanDirCbReportPresence(SlruCtl ctl, char *filename, int64 segpage,
+ void *data)
{
- int cutoffPage = *(int *) data;
+ int64 cutoffPage = *(int64 *) data;
SlruMayDeleteSegment, called from this function, still thinks page
numbers as int.

if ((len == 4 || len == 5 || len == 6) &&
strspn(clde->d_name, "0123456789ABCDEF") == len)
{
- segno = (int) strtol(clde->d_name, NULL, 16);
+ segno = strtoi64(clde->d_name, NULL, 16);
(I'm not sure about "len == 5 || len == 6", though), the name of the
file is (I think) now expanded to 12 bytes. Otherwise, strtoi64 is
not needed here.

-/* Currently, no field of AsyncQueueEntry requires more than int alignment */
-#define QUEUEALIGN(len) INTALIGN(len)
+/* AsyncQueueEntry.xid requires 8-byte alignment */
+#define QUEUEALIGN(len) TYPEALIGN(8, len)
I think we haven't expanded xid yet? (And the first member of
AsyncQueueEntry is int even after expanding xid.)