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Date:   Thu, 7 Nov 2019 17:27:12 -0500
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     "J. Bruce Fields" <bfields@redhat.com>
Cc:     Trond Myklebust <trondmy@hammerspace.com>,
        "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH v2] nfsd: Fix races between nfsd4_cb_release() and
 nfsd4_shutdown_callback()
Message-ID: <20191107222712.GB10806@fieldses.org>
References: <20191023214318.9350-1-trond.myklebust@hammerspace.com>
 <20191025145147.GA16053@pick.fieldses.org>
 <97f56de86f0aeafb56998023d0561bb4a6233eb8.camel@hammerspace.com>
 <20191025152119.GC16053@pick.fieldses.org>
 <20191025153336.GA20283@fieldses.org>
 <20191029214705.GA29280@fieldses.org>
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On Tue, Oct 29, 2019 at 05:47:05PM -0400, J. Bruce Fields wrote:
> On Fri, Oct 25, 2019 at 11:33:36AM -0400, bfields wrote:
> > On Fri, Oct 25, 2019 at 11:21:19AM -0400, J. Bruce Fields wrote:
> > > I thought I was running v2, let me double-check....
> > 
> > Yes, with v2 I'm getting a hang on generic/013.
> > 
> > I checked quickly and didn't see anything interesting in the logs,
> > otherwise I haven't done any digging.
> 
> Reproduceable just with ./check -nfs generic/013.  The last thing I see
> in wireshark is an asynchronous COPY call and reply.  Which means it's
> probably trying to do a CB_OFFLOAD.  Hm.

Oh, I think it just needs the following.

--b.

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index fb71e7f9d0d9..e49604701a71 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -1026,8 +1026,8 @@ static bool nfsd41_cb_get_slot(struct nfsd4_callback *cb, struct rpc_task *task)
 			return false;
 		}
 		rpc_wake_up_queued_task(&clp->cl_cb_waitq, task);
-		cb->cb_holds_slot = true;
 	}
+	cb->cb_holds_slot = true;
 	return true;
 }