linux-kernel - Re: [PATCH v2 05/17] locks: generic_delete_lease doesn't need a file

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Date:	Thu, 4 Sep 2014 20:29:26 -0400
From:	Jeff Layton <jeff.layton@...marydata.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
	"J. Bruce Fields" <bfields@...ldses.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 05/17] locks: generic_delete_lease doesn't need a
 file_lock at all

On Thu, 4 Sep 2014 13:14:24 -0700
Christoph Hellwig <hch@...radead.org> wrote:

> On Thu, Sep 04, 2014 at 08:38:31AM -0400, Jeff Layton wrote:
> > Ensure that it's OK to pass in a NULL file_lock double pointer on
> > a F_UNLCK request and convert the vfs_setlease F_UNLCK callers to
> > do just that.
> > 
> > Finally, turn the BUG_ON in generic_setlease into a WARN_ON_ONCE
> > with an error return. That's a problem we can handle without
> > crashing the box if it occurs.
> 
> Can we just make generic_delete_lease (maye renamed to vfs_delete_lease)
> the interface for deleting leases instead of going through a useless
> multiplex and file operation?
> 

I'm not sure that change really makes sense to me at this point.

Suppose we have an exportable filesystem with a ->setlease
implementation [1]. We end up calling into it to set up a lease and it
calls generic_add_lease. If we make the change you're suggesting, then
we'll have no parallel to a ->setlease op when removing that lease.

We could of course make a ->dellease op or something, but I'd rather
not introduce that change until I've had a chance to do some other
cleanup to the file locking infrastructure.

So...I'm not opposed to doing what you suggest, but I'd rather not do it
just yet until I've gotten a little farther with some other cleanup of
how we deal with locks in general. I think it'll be easier to do that
once some other changes have gone in.

I'll post a draft patchset based on those changes "real soon now" as an
RFC. Hopefully at that point my rationale will make a bit more sense...

[1]: of course, only cifs has a non-trivial one for now and it's pretty
half-assed...

-- 
Jeff Layton <jlayton@...marydata.com>
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