Re: [PATCH 0/3] Eliminate delegation self-conflicts

From: Chuck Lever <chuck.lever@oracle.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: "J. Bruce Fields" <bfields@redhat.com>,
	Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Trond Myklebust <trond.myklebust@primarydata.com>
Subject: Re: [PATCH 0/3] Eliminate delegation self-conflicts
Date: Tue, 29 Aug 2017 19:39:14 -0400	[thread overview]
Message-ID: <287C6A02-4C3D-4BC8-AA63-A7AAB3F21564@oracle.com> (raw)
In-Reply-To: <20170829215209.GA13385@fieldses.org>

> On Aug 29, 2017, at 5:52 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> 
> On Sat, Aug 26, 2017 at 02:06:05PM -0400, Chuck Lever wrote:
>> 
>>> On Aug 25, 2017, at 5:52 PM, J. Bruce Fields <bfields@redhat.com> wrote:
>>> 
>>> From: "J. Bruce Fields" <bfields@redhat.com>
>>> 
>>> This is my attempt to fix the NFS server so we don't unnecessarily
>>> recall delegations when the operation breaking the delegation comes from
>>> the same client that holds the delegation.
>>> 
>>> To do that we need some way to pass the identity of the breaker down
>>> through the VFS.
>>> 
>>> I didn't feel like adding another argument to all the VFS functions that
>>> this might need to be passed down through.  But all of those functions
>>> already take a struct inode **delegated inode, so instead I turned that
>>> into a single-member struct deleg_ctrl *, which I then added a second
>>> member to.
>>> 
>>> I dunno, welcome any more straightforward ways of doing this if anyone
>>> has suggestions.
>>> 
>>> My first attempt was to do this by instead checking for conflicts in the
>>> caller (nfsd) and then passing down one just one bit telling the lease
>>> code conflicts had already been checked so it didn't need to.  But
>>> that's much too early to check for conflicts, since the caller doesn't
>>> have the necessary inode locks yet.
>>> 
>>> I'm still missing testing.  Regression tests pass, but I haven't
>>> actually confirmed that the self-conflicts are gone!  Off to go hack on
>>> pynfs....
>> 
>> FWIW, I observe a lot of delegation recall activity when running
> 
> How are you measuring that?

My observation is based on wire traces.

>> the git regression tests on an NFSv4.x mount. This is a single
>> client.
> 
>> 
>> Unpack a recent release of the git tarball.
>> 
>> $ cd src/git
>> $ make clean
>> $ make
>> $ make test
>> 
>> Easily scriptable, and you can "cd t/" and run individual
>> regression tests if you like.
> 
> Thanks, I'll look into that.
> 
> --b.

--
Chuck Lever