#ifdef POWERGRES

static Dllist *rnodes = NULL;
static volatile slock_t mylock = 0;

typedef struct {
	RelFileNode rnode;
	BlockNumber blkno;
} RelSegInfo;

#undef calloc
#undef malloc
#undef free
#undef realloc
#undef strdup

/*
 * Add segment file names to the internal table
 */
static void add_file(RelFileNode rnode, BlockNumber blkno)
{
	Dlelem *elm;
	RelSegInfo *info;

#ifndef LET_OS_MANAGE_FILESIZE
	BlockNumber segno, isegno;
#endif

	SpinLockAcquire_NoHoldoff(&mylock);

	if (rnodes == NULL)
	{
		rnodes = DLNewList();
	}

	elm = DLGetHead(rnodes);
	while (elm)
	{
		RelSegInfo *ip = (RelSegInfo *)DLE_VAL(elm);
#ifndef LET_OS_MANAGE_FILESIZE
		segno = blkno / ((BlockNumber) RELSEG_SIZE);
		isegno = ip->blkno / ((BlockNumber) RELSEG_SIZE);
#endif
		if (((ip->rnode.tblNode == (Oid)0 && rnode.tblNode == (Oid)0 && ip->rnode.relNode == rnode.relNode) ||
			 (ip->rnode.tblNode == rnode.tblNode && ip->rnode.relNode == rnode.relNode))
#ifndef LET_OS_MANAGE_FILESIZE
			&& segno == isegno
#endif
			)
		{
			/* already there */
			SpinLockRelease_NoHoldoff(&mylock);
			return;
		}
		elm = DLGetSucc(elm);
	}

	info = malloc(sizeof(*info));
	if (info == NULL)
	{
		elog(ERROR, "add_file: malloc failed");
	}
	else
	{
		info->rnode = rnode;
		info->blkno = blkno;
		DLAddHead(rnodes, DLNewElem(info));
	}
	SpinLockRelease_NoHoldoff(&mylock);
}

/*
 * fsync all file segments registered in the table
 */
#include <fcntl.h>
static void checkpoint_buffer_sync(void)
{
	Dllist *segs;
	Dlelem *elm;
	File fd;
	char segname[MAXPGPATH];
#ifndef LET_OS_MANAGE_FILESIZE
	BlockNumber segno;
#endif

	if (rnodes == NULL)
		return;

	SpinLockAcquire_NoHoldoff(&mylock);

	segs = DLNewList();

	elm = DLGetHead(rnodes);
	while (elm)
	{
		Dlelem *next;

		next = DLGetSucc(elm);
 
		DLAddHead(segs, DLNewElem(DLE_VAL(elm)));
		DLRemove(elm);
		DLFreeElem(elm);

		elm = next;
	}

	SpinLockRelease_NoHoldoff(&mylock);

	elm = DLGetHead(segs);
	while (elm)
	{
		RelSegInfo *ip = (RelSegInfo *)DLE_VAL(elm);

		if (ip->rnode.tblNode == (Oid) 0)		/* "global tablespace" */
		{
			/* Shared system relations live in {datadir}/global */
			snprintf(segname, MAXPGPATH, "%s/global/%u", DataDir, ip->rnode.relNode);
		}
		else
		{
			snprintf(segname, MAXPGPATH, "%s/base/%u/%u", DataDir, ip->rnode.tblNode, ip->rnode.relNode);
		}

#ifndef LET_OS_MANAGE_FILESIZE
		/* append the '.segno', if needed */
		segno = ip->blkno / ((BlockNumber) RELSEG_SIZE);
		if (segno > 0)
		{
			snprintf(segname, MAXPGPATH, "%s.%u", segname, segno);
		}
#endif
		fd = FileNameOpenFile(segname, O_RDWR | PG_BINARY, 0600);
		if (fd >= 0)
		{
			elog(DEBUG1,"flushing %s", segname);
			FileSync(fd);
			FileClose(fd);
		}
		elm = DLGetSucc(elm);
	}
	DLFreeList(segs);
}
#endif /* POWERGRES */