Trond,
> Von: Trond Myklebust <[email protected]>
>
> to den 11.08.2005 Klokka 14:27 (+0200) skreiv Michael Kerrisk:
> > And I pointed out that the existing behaviour (which is
> > still current in 2.6.13-rc4) is inconsistent:
> >
> > http://marc.theaimsgroup.com/?l=linux-kernel&m=111511455406623&w=2
> >
> > Some further testing showed the following (both open()
> > and fcntl(F_SETLEASE) from same process):
> >
> > open() | lease requested
> > flag | F_RDLCK | F_WRLCK
> > ---------+----------+----------
> > O_RDONLY | okay | okay
> > O_WRONLY | EAGAIN | okay
> > O_RDWR | EAGAIN | okay
> >
> > In other words, a process can open a file read-write, and
> > can't place a read lease, but can place a write lease!
> > That does not seem to make any sense to me.
>
> Then what do you think that leases are supposed to do, and why?
As noted already, I don't know much of CIFS and SAMBA.
But are you saying that it is sensible and consistent that
"a process can open a file read-write, and can't place a
read lease, but can place a write lease"?
> An exclusive (i.e. write) lease should mean that _nothing_ other than
> your process is accessing the file. A client may cache the file data,
> metadata and read/write locks because nobody else can change that
> information, and nobody else holds locks on the file. It may also cache
> file acl/access information, and hence cache new OPEN calls.
>
> A shared (i.e. read) lease means that there are currently no processes
> that can change the data or metadata (including your own).
^^^^^^^^^^^^^^^^^
This is precisely the point of the problem. Stephen
Rothwell, and Matthew Wilcox seem to be saying that
the last bit is not the case.
Cheers,
Michael
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