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NeilBrown
4a9be28c45
If the last NFSv3 unmount from a given host races with a mount from the
same host, we can destroy an nlm_host that is still in use.
Specifically nlmclnt_lookup_host() can increment h_count on
an nlm_host that nlmclnt_release_host() has just successfully called
refcount_dec_and_test() on.
Once nlmclnt_lookup_host() drops the mutex, nlm_destroy_host_lock()
will be called to destroy the nlmclnt which is now in use again.
The cause of the problem is that the dec_and_test happens outside the
locked region. This is easily fixed by using
refcount_dec_and_mutex_lock().
Fixes: 8ea6ecc8b0 ("lockd: Create client-side nlm_host cache")
Cc: [email protected] (v2.6.38+)
Signed-off-by: NeilBrown <[email protected]>
Signed-off-by: Trond Myklebust <[email protected]>