Created attachment 951441 [details]
Patch to make quick-read invalidate its cache when requested

This is one of the "other bugs" mentioned in bug #1158120.

When running the same example as in that bug report on a filesystem mounted with o-direct, with that patch applied, then the output is sometimes correct

$ echo init > $D/f; cat $D/f; ssh $OTHER_HOST "echo second > $D/$f"; cat $D/f
init
second

but sometimes gives

$ echo init > $D/f; cat $D/f; ssh $OTHER_HOST "echo second > $D/$f"; cat $D/f
init
init
d

This is because the quick-read translator does not respond to cache invalidation requests. The attached patch makes it listen to invalidation requests and discard its cache.