From ca857cc1d4cf17aba4bbb3b95d35454ad96924b3 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <trond.myklebust@primarydata.com>
Date: Tue, 28 Jun 2016 13:54:09 -0400
Subject: NFS/pnfs: Do not clobber existing pgio_done_cb in
 nfs4_proc_read_setup

If a pNFS client sets hdr->pgio_done_cb, then we should not overwrite that
in nfs4_proc_read_setup()

Fixes: 75bf47ebf6b5 ("pNFS/flexfile: Fix erroneous fall back to...")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index ff416d0..6191b7e 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4392,7 +4392,8 @@ static void nfs4_proc_read_setup(struct nfs_pgio_header *hdr,
 				 struct rpc_message *msg)
 {
 	hdr->timestamp   = jiffies;
-	hdr->pgio_done_cb = nfs4_read_done_cb;
+	if (!hdr->pgio_done_cb)
+		hdr->pgio_done_cb = nfs4_read_done_cb;
 	msg->rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_READ];
 	nfs4_init_sequence(&hdr->args.seq_args, &hdr->res.seq_res, 0);
 }
-- 
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