Function BufferGetTag

src/backend/storage/buffer/bufmgr.c:2933–2951

* BufferGetTag * Returns the relfilenode, fork number and block number associated with * a buffer. */

 *		a buffer.
 */
void
BufferGetTag(Buffer buffer, RelFileNode *rnode, ForkNumber *forknum,
			 BlockNumber *blknum)
{
	BufferDesc *bufHdr;

	/* Do the same checks as BufferGetBlockNumber. */
	Assert(BufferIsPinned(buffer));

	if (BufferIsLocal(buffer))
		bufHdr = GetLocalBufferDescriptor(-buffer - 1);
	else
		bufHdr = GetBufferDescriptor(buffer - 1);

	/* pinned, so OK to read tag without spinlock */
	*rnode = bufHdr->tag.rnode;
	*forknum = bufHdr->tag.forkNum;
	*blknum = bufHdr->tag.blockNum;
}

/*
 * FlushBuffer