On 8/5/2016 8:53 AM, Glen Barber wrote: > On Fri, Aug 05, 2016 at 06:23:06AM +0000, Andriy Gapon wrote: >> Author: avg >> Date: Fri Aug 5 06:23:06 2016 >> New Revision: 303763 >> URL: https://svnweb.freebsd.org/changeset/base/303763 >> >> Log: >> zfs: honour and make use of vfs vnode locking protocol >> >> ZFS POSIX Layer is originally written for Solaris VFS which is very >> different from FreeBSD VFS. Most importantly many things that FreeBSD VFS >> manages on behalf of all filesystems are implemented in ZPL in a different >> way. >> Thus, ZPL contains code that is redundant on FreeBSD or duplicates VFS >> functionality or, in the worst cases, badly interacts / interferes >> with VFS. >> >> The most prominent problem is a deadlock caused by the lock order reversal >> of vnode locks that may happen with concurrent zfs_rename() and lookup(). >> The deadlock is a result of zfs_rename() not observing the vnode locking >> contract expected by VFS. >> >> This commit removes all ZPL internal locking that protects parent-child >> relationships of filesystem nodes. These relationships are protected >> by vnode locks and the code is changed to take advantage of that fact >> and to properly interact with VFS. >> >> Removal of the internal locking allowed all ZPL dmu_tx_assign calls to >> use TXG_WAIT mode. >> >> Another victim, disputable perhaps, is ZFS support for filesystems with >> mixed case sensitivity. That support is not provided by the OS anyway, >> so in ZFS it was a buch of dead code. >> >> To do: >> - replace ZFS_ENTER mechanism with VFS managed / visible mechanism >> - replace zfs_zget with zfs_vget[f] as much as possible >> - get rid of not really useful now zfs_freebsd_* adapters >> - more cleanups of unneeded / unused code >> - fix / replace .zfs support >> >> PR: 209158 >> Reported by: many >> Tested by: many (thank you all!) >> MFC after: 5 days >> Sponsored by: HybridCluster / ClusterHQ >> Differential Revision: https://reviews.freebsd.org/D6533 >> > > Thank you very much for working on this. >
Yes agreed. It scares me, but releasing with trivial deadlocks that we cannot EN due to that risk scares me more. FreeBSD's ZFS is a huge selling point for it and we want to maintain that. -- Regards, Bryan Drewery
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