On Mon, Aug 29, 2016 at 7:37 PM, Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote: > On Mon, Aug 29, 2016 at 06:50:05PM -0700, Dan Williams wrote: >> [ Adding Darrick on the off chance that this triggers an "aha, of >> course it does!" ] > > Aha! Of course it does!!! :) Heh, thanks :). And apologies to Dave for missing his earlier note pointing out the delalloc failure, linux-nvdimm list ate the response. > >> Darrick these corruption tests you added to xfstests last year all >> fail the same way with DAX enabled. They spew: >> >> "pwrite64: Structure needs cleaning" >> >> ...reports that are cleaned up by running without "-o dax". > > I think this happens because in non-dax mode, the pwrite is a buffered > write and so long as we can create a delalloc reservation, everything > is ok and nothing fails. Whereas for dax we have to allocate the > blocks for the pwrite immediately, thereby triggering the cntbt > verifier error. > > Proceeding from the assumption "DAX behaves a lot like DIO", all the > tests that rely on buffered mode semantics are going to choke if DAX > is turned on without them knowing about it. > >> Alternatively you could sit back and watch me try to figure it out, >> that should be quite entertaining... as a start I'll try to pin down a >> stack trace when the error is returned. > > As for how to fix this, probably the best option is to change line 98 > to 'pwrite -W -S 0x62...' and update the output to include the > 'structure needs cleaning' message. I'll give it a shot. > Or get rid of the mount option and require explicitly turning on DAX > on a per-inode basis, which I think is where Dave is already going. Yes, I think we can't run away from the dax mount option fast enough. The semantics are different, so an application / administrator needs to explicitly opt-in to DAX semantics per-inode otherwise we are guaranteed to cause surprises. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
