=== DF-2618 trigger mode=craft img=craft2618.img ===
MOUNT_RC=0
a
b
c
d
LS_RC=0
stat:/mnt/h2/a inum=1024 size=12
stat: /mnt/h2/b: stat: No such file or directory
STAT_AB_RC=1
stat: /mnt/h2/c: stat: No such file or directory
STAT_C_RC=1  (expect EIO-style failure: bref for b shadows c)
--- pin file b: open fd -> ip(b) holds chain [B,B+2^kb-1] in rbtree
OPEN_B_RC=0
--- stat d: base_find(D) selects overlapping b-inum bref -> chain_get(C) ->
    RB_INSERT collision with pinned chain(B) -> KASSERT chain.c:314
stat: /mnt/h2/c: stat: No such file or directory
STAT_C_RC=1 (unreachable on INVARIANTS if panic occurred)
DONE_NO_PANIC