On Fri, 2017-02-10 at 14:51 +0530, Pankaj Singh wrote: > Hi, > > I am getting a strange problem where locks are denied by NFSv3 server > even though no locks on same file where taken. > > While looking at the code it seems like NLM compares a lock by using > "pid" and other options like form - to file offset, type of lock etc. > But we are interested in "pid" because other comparison can be same > for different file_locks. > > As we know posix threads use tgid as pid for all its thread hence > NFSv3 server will can get lock request from different posix thread > but > with same pid. Hence NLM will treat the locking request as they are > coming from same process. This may result in following problems Threads that share the same process id belong, by definition, to the same process. > 1. Different threads of same process can get lock on same file. That is precisely how POSIX locks are expected to work in threaded environments. http://pubs.opengroup.org/onlinepubs/9699919799/functions/fcntl.html "An exclusive lock shall prevent any other process from setting a shared lock or an exclusive lock on any portion of the protected area." > 2. During "fl_grant" callback wrong "block" will be compared hence > this will result in lock failure even if lock is actually granted. How so? > Is this a limitation of NLM? > -- Trond Myklebust Linux NFS client maintainer, PrimaryData trond.myklebust@xxxxxxxxxxxxxxx ��.n��������+%������w��{.n�����{��w��� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
