pg_upgrade: Improve error checking in rewriteVisibilityMap.

In the old logic, if read() were to return an error, we'd silently stop
rewriting the visibility map at that point in the file.  That's safe,
but reporting the error is better, so do that instead.

Report by Andres Freund.  Patch by Masahiko Sawada, with one correction
by me.

diff --git a/src/bin/pg_upgrade/file.c b/src/bin/pg_upgrade/file.c
index 5d87408ce93572ef4ecf52fa3c6eaf2032a27570..9b25dc5b284bbd5899eedaa9294f78cbf778b56f 100644 (file)
--- a/src/bin/pg_upgrade/file.c
+++ b/src/bin/pg_upgrade/file.c
@@ -165,6 +165,7 @@ rewriteVisibilityMap(const char *fromfile, const char *tofile, bool force)
    int         dst_fd = 0;
    char        buffer[BLCKSZ];
    ssize_t     bytesRead;
+   ssize_t     totalBytesRead = 0;
    ssize_t     src_filesize;
    int         rewriteVmBytesPerPage;
    BlockNumber new_blkno = 0;
@@ -200,13 +201,23 @@ rewriteVisibilityMap(const char *fromfile, const char *tofile, bool force)
     * page is empty, we skip it, mostly to avoid turning one-page visibility
     * maps for small relations into two pages needlessly.
     */
-   while ((bytesRead = read(src_fd, buffer, BLCKSZ)) == BLCKSZ)
+   while (totalBytesRead < src_filesize)
    {
        char       *old_cur;
        char       *old_break;
        char       *old_blkend;
        PageHeaderData pageheader;
-       bool        old_lastblk = ((BLCKSZ * (new_blkno + 1)) == src_filesize);
+       bool        old_lastblk;
+
+       if ((bytesRead = read(src_fd, buffer, BLCKSZ)) != BLCKSZ)
+       {
+           close(dst_fd);
+           close(src_fd);
+           return getErrorText();
+       }
+
+       totalBytesRead += BLCKSZ;
+       old_lastblk = (totalBytesRead == src_filesize);
 
        /* Save the page header data */
        memcpy(&pageheader, buffer, SizeOfPageHeaderData);