Andriy Gapon 4ff1c77d22 zfs: overhaul zfs-vfs glue for vnode life-cycle management ... * There is no need for the delayed destruction of znodes via taskqueue, now that we do not need to fear recursion from getnewvnode into zfs_inactive and zfs_freebsd_reclaim, thus making znode/vnode state machine a bit simpler. * More complete porting of zfs_inactive from Solaris VFS model to FreeBSD vop_inactive and vop_reclaim model. All destructive actions are done in zfs_freebsd_reclaim. This allows to simplify zfs_zget logic. * Allow zfs_zget to return a doomed vnode if the current thread already has an exclusive lock on the vnode. * Clean up Solaris-isms like bailing out of reclaim/inactive on certain values of v_usecount (aka v_count) or directly messing with this counter. * Do not clear z_vnode while znode is still accessible. z_vnode should be cleared only after zfs_znode_dmu_fini. Otherwise zfs_zget may get an effectively half-deconstructed znode. This allows to simplify zfs_zget logic further. The above changes fix at least two known/reported problems: o An indefinite wait in the following code path: vgone -> VOP_RECLAIM -> zfs_freebsd_reclaim -> vnode_destroy_vobject -> put_pages -> zfs_write -> zil_commit -> zfs_zget This happened because vgone marks a vnode as VI_DOOMED before calling VOP_RECLAIM, but zfs_zget would not return a doomed vnode under any circumstances. The fix in this change is not complete as it won't fix a deadlock between two threads doing VOP_RECLAIM where one thread is in zil_commit trying to zfs_zget a znode/vnode being reclaimed by the other thread, which would be blocked trying to enter zil_commit. This type of deadlock has not been reported as of now. o An indefinite wait in the unmount path caused by a znode "falling through the cracks" in inactive+reclaim. This would happen if the znode is unlinked while its vnode is still active. To Do: pass locking flags parameter to zfs_zget, so that the zfs-vfs glue code doesn't have to re-lock a vnode but could ask for proper locking from the very start. This would also allow for the higher level code to obtain a doomed vnode when it is expected/requested. Or to avoid blocking when it is not allowed (see zil_commit example above). ffs_vgetf seems like a good source of inspiration. Tested by: Willem Jan Withagen <wjw@digiware.nl> MFC after: 6 weeks		2012-11-25 15:33:26 +00:00
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common	Merge recent zfs vendor changes, sync code and adjust userland DEBUG.	2012-09-12 18:05:43 +00:00
uts	zfs: overhaul zfs-vfs glue for vnode life-cycle management	2012-11-25 15:33:26 +00:00
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