ada90c84eb
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
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