On Wed, Jul 4, 2018 at 3:38 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Tue, Jul 03, 2018 at 10:30:40AM +0200, Ingo Molnar wrote: >> >> * Dan Williams <dan.j.williams@xxxxxxxxx> wrote: >> >> > Hi Ingo, >> > >> > Here is an additional copy_to_iter_mcsafe() fix to address the crash >> > reported by Ross. This now passes xfstests:generic/323 on my system. >> >> The lib/iov_iter fix would need an Acked-by from Al. > > I can live with that; I would really like to see some documentation on > the copy_to_iter_mcsafe(), but that's a separate story. Incidentally, > are there any expectations of other callers appearing, or is that > (and copy_from_iter_flushcache()) YASingleConsumerAPI? The current cpu architectural detail preventing conversion of the standard copy_to_iter() path to use the mcsafe flavor is that we can't use REP MOV for fast copies and instead need to use a software loop so that any exceptions are recoverable. When / if that is addressed, and there is no performance difference between the two, it might make sense to convert more users. The _flushcache flavor, however, will likely stay limited to a single consumer for the persistent memory use case.
