On Mon, Mar 10, 2014 at 01:55:23PM +1100, Dave Chinner wrote: > Changing the directory code to handle this sort of locking is going > to require a bit of surgery. However, I can see advantages to moving > directory data to the same locking strategy as regular file data - > locking heirarchies are identical, directory ilock hold times are > much reduced, we don't get lockdep whining about taking page faults > with the ilock held, etc. > > A quick hack at to demonstrate the high level, initial step of using > the IOLOCK for readdir serialisation. I've done a little smoke > testing on it, so it won't die immediately. It should get rid of all > the nasty lockdep issues, but it doesn't start to address the deeper > restructing that is needed. What synchronization do we actually need from the iolock? Pushing the ilock down to where it's actually needed is a good idea either way, though. > This would be a straight forward change, except for two things: > filestreams and lockdep. The filestream allocator takes the > directory iolock and makes assumptions about parent->child locking > order of the iolock which will now be invalidated. Hence some > changes to the filestreams code is needed to ensure that it never > blocks on directory iolocks and deadlocks. instead it needs to fail > stream associations when such problems occur. I think the right fix is to stop abusing the iolock in filestreams. To me it seems like a look inside fstrm_item_t should be fine for what the filestreams code wants if I understand it correctly. >From looking over some of the filestreams code just for a few minutes I get an urge to redo lots of it right now.. > @@ -1228,7 +1244,7 @@ xfs_create( > * the transaction cancel unlocking dp so don't do it explicitly in the > * error path. > */ > - xfs_trans_ijoin(tp, dp, XFS_ILOCK_EXCL); > + xfs_trans_ijoin(tp, dp, XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL); What do we need the iolock on these operations for? _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
