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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Benjamin Coddington <bcodding@redhat.com>,
        "trondmy@kernel.org" <trondmy@kernel.org>
CC:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH v9 03/27] NFS: Trace lookup revalidation failure
Thread-Topic: [PATCH v9 03/27] NFS: Trace lookup revalidation failure
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Date:   Wed, 9 Mar 2022 15:28:45 +0000
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> On Mar 9, 2022, at 8:42 AM, Benjamin Coddington <bcodding@redhat.com> wro=
te:
>=20
> On 24 Feb 2022, at 21:09, Trond Myklebust wrote:
>> On Thu, 2022-02-24 at 09:14 -0500, Benjamin Coddington wrote:
>>> There's a path through nfs4_lookup_revalidate that will now only produc=
e
>>> this exit tracepoint.  Does it need the _enter tracepoint added?
>>=20
>> You're thinking about the nfs_lookup_revalidate_delegated() path? The
>> _enter() tracepoint doesn't provide any useful information that isn't
>> already provided by the _exit(), AFAICS.
>=20
> No, the path through nfs4_do_lookup_revalidate(), reval_dentry: jump.  Bu=
t I
> agree there's not much value in the _enter() tracepoint.  Maybe we can
> remove it, and _exit more like _done.
>=20
> I am thinking about hearing back from folks about mis-matched _enter() an=
d
> _exit() results, but also realize this is nit-picking.

I think the _enter / _exit trace points simply replaced
dprintk call sites which did much the same reporting.
Maybe we should consider replacing some of these because
we can rely on function call tracing instead.

But generally we like to see trace points that report
exceptional events rather than "I made it to this point".
The latter category of trace points are interesting
while code is under development but often loses its
value once the code is in the field.


--
Chuck Lever