svn commit: r303970 - in stable/11/sys/cddl: compat/opensolaris/sys contrib/opensolaris/uts/common/fs/zfs contrib/opensolaris/uts/common/fs/zfs/sys

[Glen Barber]

On Fri, Aug 12, 2016 at 01:33:31AM +0300, Slawa Olhovchenkov wrote:
> On Thu, Aug 11, 2016 at 08:48:04PM +0000, Andriy Gapon wrote:
> 
> > Author: avg
> > Date: Thu Aug 11 20:48:03 2016
> > New Revision: 303970
> > URL: https://svnweb.freebsd.org/changeset/base/303970
> > 
> > Log:
> >   MFC r303763,303791,303869: 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
> 
> MFC to 10.x/9.x planed?
> 

As I understand it, this does not affect stable/10.

Glen

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