dm mpath: fix racey management of PG initialization
commit5.4-rM2-2.2.x-imx-squashedc322ee9320
upstream. Commit935fcc56ab
("dm mpath: only flush workqueue when needed") changed flush_multipath_work() to avoid needless workqueue flushing (of a multipath global workqueue). But that change didn't realize the surrounding flush_multipath_work() code should also only run if 'pg_init_in_progress' is set. Fix this by only doing all of flush_multipath_work()'s PG init related work if 'pg_init_in_progress' is set. Otherwise multipath_wait_for_pg_init_completion() will run unconditionally but the preceeding flush_workqueue(kmpath_handlerd) may not. This could lead to deadlock (though only if kmpath_handlerd never runs a corresponding work to decrement 'pg_init_in_progress'). It could also be, though highly unlikely, that the kmpath_handlerd work that does PG init completes before 'pg_init_in_progress' is set, and then an intervening DM table reload's multipath_postsuspend() triggers flush_multipath_work(). Fixes:935fcc56ab
("dm mpath: only flush workqueue when needed") Cc: stable@vger.kernel.org Reported-by: Ben Marzinski <bmarzins@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
parent
226fb99eb5
commit
b30f628bee
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@ -1190,17 +1190,25 @@ static void multipath_wait_for_pg_init_completion(struct multipath *m)
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static void flush_multipath_work(struct multipath *m)
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static void flush_multipath_work(struct multipath *m)
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{
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{
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if (m->hw_handler_name) {
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if (m->hw_handler_name) {
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set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
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unsigned long flags;
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smp_mb__after_atomic();
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if (!atomic_read(&m->pg_init_in_progress))
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goto skip;
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spin_lock_irqsave(&m->lock, flags);
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if (atomic_read(&m->pg_init_in_progress) &&
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!test_and_set_bit(MPATHF_PG_INIT_DISABLED, &m->flags)) {
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spin_unlock_irqrestore(&m->lock, flags);
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if (atomic_read(&m->pg_init_in_progress))
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flush_workqueue(kmpath_handlerd);
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flush_workqueue(kmpath_handlerd);
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multipath_wait_for_pg_init_completion(m);
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multipath_wait_for_pg_init_completion(m);
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spin_lock_irqsave(&m->lock, flags);
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clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
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clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
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smp_mb__after_atomic();
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}
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}
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spin_unlock_irqrestore(&m->lock, flags);
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}
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skip:
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if (m->queue_mode == DM_TYPE_BIO_BASED)
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if (m->queue_mode == DM_TYPE_BIO_BASED)
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flush_work(&m->process_queued_bios);
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flush_work(&m->process_queued_bios);
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flush_work(&m->trigger_event);
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flush_work(&m->trigger_event);
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