Function BufferMProtect

src/backend/storage/buffer/bufmgr.c:517–529

								  !BufferIsInvalid(buf->buf_id+1))

static inline void BufferMProtect(volatile BufferDesc *bufHdr, int protectionLevel)
{
	if (ShouldMemoryProtect(bufHdr))
	{
		if (mprotect(BufHdrGetBlock(bufHdr), BLCKSZ, protectionLevel))
		{
			ereport(ERROR,
					(errmsg("unable to set memory level to %d, error %d, "
							"block size %d, ptr %ld", protectionLevel,
							errno, BLCKSZ, (long int) BufHdrGetBlock(bufHdr))));
		}
	}
}
#endif

static inline void ReleaseContentLock(volatile BufferDesc *buf)