Function SaveSlotToPath

src/backend/replication/slot.c:1529–1678

* Shared functionality between saving and creating a replication slot. */

 * Shared functionality between saving and creating a replication slot.
 */
static void
SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)
{
	char		tmppath[MAXPGPATH];
	char		path[MAXPGPATH];
	int			fd;
	ReplicationSlotOnDisk cp;
	bool		was_dirty;

	/* first check whether there's something to write out */
	SpinLockAcquire(&slot->mutex);
	was_dirty = slot->dirty;
	slot->just_dirtied = false;
	SpinLockRelease(&slot->mutex);

	/* and don't do anything if there's nothing to write */
	if (!was_dirty)
		return;

	LWLockAcquire(&slot->io_in_progress_lock, LW_EXCLUSIVE);

	/* silence valgrind :( */
	memset(&cp, 0, sizeof(ReplicationSlotOnDisk));

	snprintf(tmppath, sizeof(tmppath), "%s/state.tmp", dir);
	snprintf(path, sizeof(path), "%s/state", dir);

	fd = OpenTransientFile(tmppath, O_CREAT | O_EXCL | O_WRONLY | PG_BINARY);
	if (fd < 0)
	{
		/*
		 * If not an ERROR, then release the lock before returning.  In case
		 * of an ERROR, the error recovery path automatically releases the
		 * lock, but no harm in explicitly releasing even in that case.  Note
		 * that LWLockRelease() could affect errno.
		 */
		int			save_errno = errno;

		LWLockRelease(&slot->io_in_progress_lock);
		errno = save_errno;
		ereport(elevel,
				(errcode_for_file_access(),
				 errmsg("could not create file \"%s\": %m",
						tmppath)));
		return;
	}

	cp.magic = SLOT_MAGIC;
	INIT_CRC32C(cp.checksum);
	cp.version = SLOT_VERSION;
	cp.length = ReplicationSlotOnDiskV2Size;

	SpinLockAcquire(&slot->mutex);

	memcpy(&cp.slotdata, &slot->data, sizeof(ReplicationSlotPersistentData));

	SpinLockRelease(&slot->mutex);