Messages in this thread |  | | | Date | Thu, 11 Aug 2005 10:14:15 +0200 (MEST) | | From | "Michael Kerrisk" <> | | Subject | Re: fcntl(F GETLEASE) semantics?? |
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> Von: Peter Chubb <peterc@gelato.unsw.edu.au> > > >>>>> "Trond" == Trond Myklebust <trond.myklebust@fys.uio.no> writes: > > Trond> to den 11.08.2005 Klokka 09:48 (+1000) skreiv Peter Chubb: > >> Hi, The LTP test fcntl23 is failing. It does, in essence, fd = > >> open(xxx, O_RDWR|O_CREAT, 0777); if (fcntl(fd, F_SETLEASE, F_RDLCK) > >> == -1) fail; > >> > >> fcntl always returns EAGAIN here. The manual page says that a read > >> lease causes notification when `another process' opens the file for > >> writing or truncates it. The kernel implements `any process' > >> (including the current one). > >> > >> Which semantics are correct? Personally I think that what the > >> kernel implements is correct (you can't get a read lease unsless > >> there are no writers _at_ _all_) > > Trond> A read lease should mean that there are no writers at all. > > Trond> If we were to allow the current process to open for write, then > Trond> that would still mean that nobody else can get a lease. In > Trond> effect you have been granted a lease with exclusive semantics > Trond> (i.e. a write lease). You might as well request that instead of > Trond> pretending it is a read lease. > > So the manual page is wrong. Fine.
No. The behavior in Linux recently, and arbitrarily (IMO) changed:
http://marc.theaimsgroup.com/?l=linux-kernel&m=111502547506310&w=2 http://marc.theaimsgroup.com/?l=linux-kernel&m=111755426027086&w=2
One of the developers of the file leases mechanism seems to have agreed that this change should not have occurred:
http://marc.theaimsgroup.com/?l=linux-kernel&m=111512619520116&w=2
but the suggested patch did not (yet) make its way into the kernel.
Stephen -- what is your take on this now?
Cheers,
Michael
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