Bonjour Michaël-san,
Yes, that would be nice, for now I have focused. For pg_resetwal yes
we could do it easily. Would you like to send a patch?
Here is a proposal for "pg_resetwal".
The implementation basically removes a lot of copy paste and calls the
new update_controlfile function instead. I like removing useless code:-)
The reserwal implementation was doing a rm/create cycle, which was leaving
a small window for losing the controlfile. Not neat.
I do not see the value of *not* fsyncing the control file when writing it,
as it is by definition very precious, so I added a fsync. The server side
branch uses the backend available "pg_fsync", which complies with server
settings there and can do nothing if fsync is disabled.
Maybe the two changes could be committed separately.
--
Fabien.
diff --git a/src/bin/pg_resetwal/pg_resetwal.c b/src/bin/pg_resetwal/pg_resetwal.c
index 2af8713216..dd085e16ab 100644
--- a/src/bin/pg_resetwal/pg_resetwal.c
+++ b/src/bin/pg_resetwal/pg_resetwal.c
@@ -918,18 +918,6 @@ PrintNewControlValues(void)
static void
RewriteControlFile(void)
{
- int fd;
- char buffer[PG_CONTROL_FILE_SIZE]; /* need not be aligned */
-
- /*
- * For good luck, apply the same static assertions as in backend's
- * WriteControlFile().
- */
- StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_MAX_SAFE_SIZE,
- "pg_control is too large for atomic disk writes");
- StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_FILE_SIZE,
- "sizeof(ControlFileData) exceeds PG_CONTROL_FILE_SIZE");
-
/*
* Adjust fields as needed to force an empty XLOG starting at
* newXlogSegNo.
@@ -961,53 +949,7 @@ RewriteControlFile(void)
ControlFile.max_prepared_xacts = 0;
ControlFile.max_locks_per_xact = 64;
- /* Contents are protected with a CRC */
- INIT_CRC32C(ControlFile.crc);
- COMP_CRC32C(ControlFile.crc,
- (char *) &ControlFile,
- offsetof(ControlFileData, crc));
- FIN_CRC32C(ControlFile.crc);
-
- /*
- * We write out PG_CONTROL_FILE_SIZE bytes into pg_control, zero-padding
- * the excess over sizeof(ControlFileData). This reduces the odds of
- * premature-EOF errors when reading pg_control. We'll still fail when we
- * check the contents of the file, but hopefully with a more specific
- * error than "couldn't read pg_control".
- */
- memset(buffer, 0, PG_CONTROL_FILE_SIZE);
- memcpy(buffer, &ControlFile, sizeof(ControlFileData));
-
- unlink(XLOG_CONTROL_FILE);
-
- fd = open(XLOG_CONTROL_FILE,
- O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
- pg_file_create_mode);
- if (fd < 0)
- {
- fprintf(stderr, _("%s: could not create pg_control file: %s\n"),
- progname, strerror(errno));
- exit(1);
- }
-
- errno = 0;
- if (write(fd, buffer, PG_CONTROL_FILE_SIZE) != PG_CONTROL_FILE_SIZE)
- {
- /* if write didn't set errno, assume problem is no disk space */
- if (errno == 0)
- errno = ENOSPC;
- fprintf(stderr, _("%s: could not write pg_control file: %s\n"),
- progname, strerror(errno));
- exit(1);
- }
-
- if (fsync(fd) != 0)
- {
- fprintf(stderr, _("%s: fsync error: %s\n"), progname, strerror(errno));
- exit(1);
- }
-
- close(fd);
+ update_controlfile(XLOG_CONTROL_FILE, progname, &ControlFile);
}
diff --git a/src/common/controldata_utils.c b/src/common/controldata_utils.c
index 71e67a2eda..78ce8b020f 100644
--- a/src/common/controldata_utils.c
+++ b/src/common/controldata_utils.c
@@ -144,9 +144,9 @@ get_controlfile(const char *DataDir, const char *progname, bool *crc_ok_p)
* update_controlfile()
*
* Update controlfile values with the contents given by caller. The
- * contents to write are included in "ControlFile". Note that it is up
- * to the caller to fsync the updated file, and to properly lock
- * ControlFileLock when calling this routine in the backend.
+ * contents to write are included in "ControlFile". Not that it is
+ * to the caller to properly lock ControlFileLock when calling this
+ * routine in the backend.
*/
void
update_controlfile(const char *DataDir, const char *progname,
@@ -216,6 +216,21 @@ update_controlfile(const char *DataDir, const char *progname,
#endif
}
+#ifndef FRONTEND
+ if (pg_fsync(fd) != 0)
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not fsync file \"%s\": %m",
+ ControlFilePath)));
+#else
+ if (fsync(fd) != 0)
+ {
+ fprintf(stderr, _("%s: could not fsync file \"%s\": %s\n"),
+ progname, ControlFilePath, strerror(errno));
+ exit(EXIT_FAILURE);
+ }
+#endif
+
#ifndef FRONTEND
if (CloseTransientFile(fd))
ereport(PANIC,
