On Tue, 2019-08-06 at 03:27 +0000, Sage Weil wrote: > On Mon, 5 Aug 2019, Jeff Layton wrote: > > xfstest generic/451 intermittently fails. The test does O_DIRECT writes > > to a file, and then reads back the result using buffered I/O, while > > running a separate set of tasks that are also doing buffered reads. > > > > The client will invalidate the cache prior to a direct write, but it's > > easy for one of the other readers' replies to race in and reinstantiate > > the invalidated range with stale data. > > Maybe a silly question, but: what if the write path did the invalidation > after the write instead of before? Then any racing read will see the new > data on disk. > I tried that originally. It reduces the race window somewhat, but it's still present since a reply to a concurrent read can get in just after the invalidation occurs. You really do have to serialize them to fix this, AFAICT. -- Jeff Layton <jlayton@xxxxxxxxxx>
