nfsd: don't return an unhashed lock stateid after taking mutex
nfsd4_lock will take the st_mutex before working with the stateid it gets, but between the time when we drop the cl_lock and take the mutex, the stateid could become unhashed (a'la FREE_STATEID). If that happens the lock stateid returned to the client will be forgotten. Fix this by first moving the st_mutex acquisition into lookup_or_create_lock_state. Then, have it check to see if the lock stateid is still hashed after taking the mutex. If it's not, then put the stateid and try the find/create again. Signed-off-by: NJeff Layton <jlayton@redhat.com> Tested-by: NAlexey Kodanev <alexey.kodanev@oracle.com> Cc: stable@vger.kernel.org # feb9dad5 nfsd: Always lock state exclusively. Cc: stable@vger.kernel.org Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>
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