From: Michael Paquier <michael@paquier.xyz>
Date: Thu, 25 Dec 2025 23:41:56 +0000 (+0900)
Subject: Upgrade BufFile to use int64 for byte positions
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bde3a4616072534fd03c75f9019d5165665ed211;p=thirdparty%2Fpostgresql.git

Upgrade BufFile to use int64 for byte positions

This change has the advantage of removing some weird type casts, caused
by offset calculations based on pgoff_t but saved as int (on older
branches we use off_t, which could be 4 or 8 bytes depending on the
environment).  These are safe currently because capped by
MAX_PHYSICAL_FILESIZE, but we would run into problems when to make
MAX_PHYSICAL_FILESIZE larger or allow callers of these routines to use a
larger physical max size on demand.

While on it, this improves BufFileDumpBuffer() so as we do not use an
offset for "availbytes".  It is not a file offset per-set, but a number
of available bytes.

This change should lead to no functional changes.

Author: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/aUStrqoOCDRFAq1M@paquier.xyz
---

diff --git a/src/backend/storage/file/buffile.c b/src/backend/storage/file/buffile.c
index 85b316d879d..9fc37092132 100644
--- a/src/backend/storage/file/buffile.c
+++ b/src/backend/storage/file/buffile.c
@@ -93,8 +93,8 @@ struct BufFile
 	 */
 	int			curFile;		/* file index (0..n) part of current pos */
 	pgoff_t		curOffset;		/* offset part of current pos */
-	int			pos;			/* next read/write position in buffer */
-	int			nbytes;			/* total # of valid bytes in buffer */
+	int64		pos;			/* next read/write position in buffer */
+	int64		nbytes;			/* total # of valid bytes in buffer */
 
 	/*
 	 * XXX Should ideally use PGIOAlignedBlock, but might need a way to avoid
@@ -493,8 +493,8 @@ BufFileLoadBuffer(BufFile *file)
 static void
 BufFileDumpBuffer(BufFile *file)
 {
-	int			wpos = 0;
-	int			bytestowrite;
+	int64		wpos = 0;
+	int64		bytestowrite;
 	File		thisfile;
 
 	/*
@@ -503,7 +503,7 @@ BufFileDumpBuffer(BufFile *file)
 	 */
 	while (wpos < file->nbytes)
 	{
-		pgoff_t		availbytes;
+		int64		availbytes;
 		instr_time	io_start;
 		instr_time	io_time;
 
@@ -524,8 +524,8 @@ BufFileDumpBuffer(BufFile *file)
 		bytestowrite = file->nbytes - wpos;
 		availbytes = MAX_PHYSICAL_FILESIZE - file->curOffset;
 
-		if ((pgoff_t) bytestowrite > availbytes)
-			bytestowrite = (int) availbytes;
+		if (bytestowrite > availbytes)
+			bytestowrite = availbytes;
 
 		thisfile = file->files[file->curFile];
 
@@ -794,7 +794,7 @@ BufFileSeek(BufFile *file, int fileno, pgoff_t offset, int whence)
 		 * whether reading or writing, but buffer remains dirty if we were
 		 * writing.
 		 */
-		file->pos = (int) (newOffset - file->curOffset);
+		file->pos = (int64) (newOffset - file->curOffset);
 		return 0;
 	}
 	/* Otherwise, must reposition buffer, so flush any dirty data */
@@ -983,10 +983,10 @@ BufFileTruncateFileSet(BufFile *file, int fileno, pgoff_t offset)
 	{
 		/* No need to reset the current pos if the new pos is greater. */
 		if (newOffset <= file->curOffset + file->pos)
-			file->pos = (int) (newOffset - file->curOffset);
+			file->pos = (int64) newOffset - file->curOffset;
 
 		/* Adjust the nbytes for the current buffer. */
-		file->nbytes = (int) (newOffset - file->curOffset);
+		file->nbytes = (int64) newOffset - file->curOffset;
 	}
 	else if (newFile == file->curFile &&
 			 newOffset < file->curOffset)