remove() is the function used to remove every reference to a cf from
the compaction manager. This function works by removing cf from the
queue, and waiting for possible ongoing compaction on cf.
However, a cf may be re-queued by compaction manager task if there
is pending compaction by the end of compaction.
If cf is still referenced by the time remove() returns, we could end
up with an use-after-free. To fix that, a task shouldn't re-queue a
cf if it was asked to stop. The stat pending_tasks was also not
being updated when a cf was removed from the task queue.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
c2a98807c7