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 85b316d879dc0a8a6f7e9542ed22d5e8cec2d2d7..9fc370921322cfcfb67981c210fa87f70749d81a 100644 (file)
--- 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)