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SubjectRe: fcntl: F_SETLEASE/F_RDLCK question
Date
From
> > > On Tue, May 03, 2005 at 09:55:42AM -0400, William A.(Andy) Adamson
> > > wrote:
> > > > i believe the current implementation is correct. opening a file for
> > > > write
> > > > means that you can not have a read lease, caller included.
> > >
> > > Why not? Certainly, others will not be able to take out a read lease,
> > > so there's very little point to only having a read lease, but I don't
> > > see why we should deny it.
> > >
> >
> > by definition: a read lease means there are no writers. so, the question
> > is
> > not 'why not', the question is why? why hand out a read lease to an open
> > for write?
>
> Andy,
>
> Look more closely at my earlier table.
>
> Regardless of what the answer to your question is, the
> current semantics are bizarre. As things stand, a process
> can open a file O_RDWR, and and can place a WRITE lease
> but not a READ lease. That can't be right.

yes - i was being too strict. looking at NFSv4 delegations; a read lease does
not mean there are no writers, it means there are no other clients (fl_owners)
writing.

the other side of the coin would be break_lease. it should not break a read
lease on an open for write in the case where the fl_owner of the read lease is
also the owner of the open for write.

-->Andy

>
> FWIW it's worth, I think the read lease should be allowed.
> Oplocks are concerned with what other processes are doing,
> not what the caller is doing. Also, the current semantcis
> break backward compatibility.
>
> Cheers,
>
> Michael
>
> --
> +++ Neu: Echte DSL-Flatrates von GMX - Surfen ohne Limits +++
> Always online ab 4,99 Euro/Monat: http://www.gmx.net/de/go/dsl


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