HAMMER panic while running fsstress; mutual recursion rooted at hammer_flusher_slave_thread
While running fsstress on a HAMMER fs on an up-to-date Dfly, I hit a panic -
hammer_flush_inode_done called hammer_setup_parent_inodes, which called
hammer_setup_parent_inodes_helper, which calls hammer_setup_parent_inodes, ...
all the way till we panic.
http://acm.jhu.edu/~me/hammer_fsstress_panic_20100416/ has the coredump and