Date: Fri, 12 Aug 2016 02:20:25 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Glen Barber <gjb@FreeBSD.org> Cc: svn-src-stable@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, svn-src-stable-11@freebsd.org, Andriy Gapon <avg@FreeBSD.org> Subject: Re: svn commit: r303970 - in stable/11/sys/cddl: compat/opensolaris/sys contrib/opensolaris/uts/common/fs/zfs contrib/opensolaris/uts/common/fs/zfs/sys Message-ID: <20160811232025.GG22212@zxy.spb.ru> In-Reply-To: <20160811231317.GH51184@FreeBSD.org> References: <201608112048.u7BKm4OH076291@repo.freebsd.org> <20160811223331.GF22212@zxy.spb.ru> <20160811223637.GE51184@FreeBSD.org> <20160811225202.GI8192@zxy.spb.ru> <20160811225723.GG51184@FreeBSD.org> <20160811230747.GJ8192@zxy.spb.ru> <20160811231317.GH51184@FreeBSD.org>
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On Thu, Aug 11, 2016 at 11:13:17PM +0000, Glen Barber wrote: > On Fri, Aug 12, 2016 at 02:07:47AM +0300, Slawa Olhovchenkov wrote: > > On Thu, Aug 11, 2016 at 10:57:23PM +0000, Glen Barber wrote: > > > > > On Fri, Aug 12, 2016 at 01:52:02AM +0300, Slawa Olhovchenkov wrote: > > > > On Thu, Aug 11, 2016 at 10:36:37PM +0000, Glen Barber wrote: > > > > > > > > > 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. > > > > > > > > Sure? > > > > I think ZFS/VFS layers don't change between 9.x and 11.x > > > > > > > > > > No, but as I understand it, a commit to head tickled this bug. avg@ can > > > correct me if I am wrong. > > > > May be I am wrong, I see messages about like issuses in 9.x/10.x. > > As I understund this is more clear implementation. > > Also, unification in 12.x/10.x take benefit for MFC other ZFS diffs. > > > > I agree with you. I am just unsure if this particular bug affects 10.x > and 9.x. What purpose to limit (?) MFC to 9.x/10.x to bug fix only? Or I am missing some in ypu point?
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