On 18/09/2019 15:31, Jan Kara wrote: <> >>> Is there a test on xfstests to demonstrate this race? >> >> No, but I can try to create one. > > I was experimenting with this but I could not reproduce the issue in my > test VM without inserting artificial delay at appropriate place... So I > don't think there's much point in the fstest for this. > > Honza > If I understand correctly you will need threads that direct-write files, then fadvise(WILL_NEED) - in parallel to truncate (punch_hole) these files - In parallel to trash caches. (Direct-write is so data is not present in cache when you come to WILL_NEED it into the cache, otherwise the xfs b-trees are not exercised. Or are you more worried about the page_cache races? ) Also the d-writes might want to exercise multiple size extents + holes as well. I have a very different system but its kind of the test we did for this problem. The reason it is never hit is because fadvise(WILL_NEED) is never really used that much, and there are no applications that actually blindly truncate during IO, this is only us in testing that do this meaningless thing. Thanks Jan again for working on this Boaz
