Hi Frank,
I think there are cases where a touch/chmod on a file causes it to be
opened forever in ganesha (until we are over the FD limit). This will
prevent other applications such as Samba from opening the file and sharing
it through SMB protocol to windows clients. Samba uses SETLEASE to get
notified if other applications open the file. Ganesha also may have to do
something similar to get notified and close cached FDs. The challenge is to
map FD to MDCACHE object so that it can call close() on that object. One
way to map FD to a path (using readlink) and then convert that to export
and relative path. Given export and relative path, FSAL could return a key
for that which can be used to lookup the object in MDCACHE. Is there a
better way?
Here is the relevant Samba code that implements SETLEASE and signal
handler:
https://github.com/samba-team/samba/blob/master/source3/smbd/oplock_linux.c
Thanks,
Pradeep
On Wed, Mar 7, 2018 at 7:18 AM, Frank Filz <ffilz...@mindspring.com> wrote:
> Unfortunately out in the real world, people want to mix POSIX and
> Microsoft semantics…
>
>
>
> So we do the best we can.
>
>
>
> I wonder how much of the multi-protocol use falls into two camps:
>
>
>
> 1. Simple file sharing, for example, I run Virtual Box on a Windows
> machine to get Linux VMs. I mount my Windows “My Documents” into the Linux
> VM so I can easily pass files back and forth. Share reservations work and
> prevent Linux from trampling things if Microsoft Word happens to have a
> file open.
>
> 2. Some kind of database application with clients on multiple
> platforms. Such application will use appropriate synchronizing operations
> including byte range locks in a way that does not depend on any of the
> peculiarities of POSIX or Microsoft semantics.
>
>
>
> Yea, we can try to make things like delete of open files work as best as
> possible, but either of those two use cases won’t have any really big
> surprises if the integration for a peculiarity like deleting an open file
> isn’t perfect.
>
>
>
> Now one use case that may not go so well is an application that uses lock
> files to indicate which client or process is active…
>
>
>
> I’ve seen folks paranoid that POSIX byte range locks are only advisory,
> but outside of a program bug, if a POSIX app and a Windows app are both
> using byte range locks to protect records they are changing, it doesn’t
> matter that POSIX thinks they are only advisory… Of course a server CAN
> enforce the range locks (and NFS v4 even supports this idea), and yea, that
> will break a POSIX app that thought it didn’t actually need to respect the
> locks.
>
>
>
> I think overall Ganesha does a pretty good job. There are places where it
> can do better.
>
>
>
> While talk of having an SMB front end to Ganesha are fun, I doubt we will
> ever do that, and I don’t think it’s necessary to have sufficiently good
> integration to cover 99.9% of the possible multi-protocol use cases.
>
>
>
> Frank
>
>
>
> *From:* DENIEL Philippe [mailto:philippe.den...@cea.fr]
> *Sent:* Wednesday, March 7, 2018 6:28 AM
> *To:* Pradeep <pradeeptho...@gmail.com>; nfs-ganesha-devel <
> nfs-ganesha-devel@lists.sourceforge.net>
> *Subject:* Re: [Nfs-ganesha-devel] Multiprotocol support in ganesha
>
>
>
> Hi,
>
> from a "stratospheric" point of view, I see a potentially big issue ahead
> for such a feature : FSAL has been designed to be quite close to POSIX
> behavior, CIFS follows the Microsoft File System semantics, which is pretty
> different from POSIX.
> My experience with 9p integration in Ganesha shows some issues in POSIX
> corner cases (like "delete on close" situations), I can't imagine what
> integrating a CIFS support would mean.
> Years ago, Tom Tapley came to bake-a-thon (this was a few months after he
> joined Microsoft Research) and he talked about issues met by Microsoft to
> implement a NFSv4 support, because of Microsoft semantics. He found many,
> but was quite optimistic. Current state : Windows has no NFS support and
> code developed at CITI (e.g. NFSv4 clients for Windos) were not pushed to
> Windows.
> Microsoft is not POSIX and POSIX is not Microsoft. They live in two very
> different worlds, and it's probably better so ;-)
>
> Regards
>
> Philippe
>
> On 03/06/18 18:20, Pradeep wrote:
>
> Hello,
>
>
>
> Is there plans to implement multiprotocol (NFS and CIFS accessing same
> export/share) in ganesha? I believe current FD cache will need changes to
> support that.
>
>
>
> Thanks,
>
> Pradeep
>
>
>
>
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