buffer cache bug?

[sri-unix!dan at BBN-UNIX]

There seems to be a bug in V7 and Berkeley VAX-UNIX buffer cache
management. There's an optimization flag B_AGE which is set to
indicate that when a buffer is freed, it should be put at the
head of the free list, where it will be immediately reused, because
it's not likely to be wanted again soon. But bwrite clears the
B_AGE bit before releasing the buffer, cancelling any attempts
at buffer management when writing. Seems to me that it should
just leave it alone. Comments? (V7 UNIX uses this bit only on reads,
so the bug doesn't matter there, but Berkeley VAX-UNIX attempts to use
it on writes as well, where it is currently having no effect.)
	Dan Franklin