HB lock takes inclusive metadata lock, which is taken also by metadata
flush, thus trying to call metadata flush under HB lock attempts to take
this lock recursively. In that case, if in the meantime some other thread
would try to take exclusive metadata lock, the inner inclusive lock would
block (because the lock keeps the order), with outer inclusive lock still
held, leading to a deadlock.
Signed-off-by: Robert Baldyga <robert.baldyga@huawei.com>
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