linux-kernel - [PATCH 3.12 168/235] NFSv4.1: nfs4_fl_prepare_ds must be careful about reporting success.

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Date:   Fri, 27 Jan 2017 11:55:01 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, NeilBrown <neilb@...e.com>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 168/235] NFSv4.1: nfs4_fl_prepare_ds must be careful about reporting success.

From: NeilBrown <neilb@...e.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit cfd278c280f997cf2fe4662e0acab0fe465f637b upstream.

Various places assume that if nfs4_fl_prepare_ds() turns a non-NULL 'ds',
then ds->ds_clp will also be non-NULL.

This is not necessasrily true in the case when the process received a fatal signal
while nfs4_pnfs_ds_connect is waiting in nfs4_wait_ds_connect().
In that case ->ds_clp may not be set, and the devid may not recently have been marked
unavailable.

So add a test for ds_clp == NULL and return NULL in that case.

Fixes: c23266d532b4 ("NFS4.1 Fix data server connection race")
Signed-off-by: NeilBrown <neilb@...e.com>
Acked-by: Olga Kornievskaia <aglo@...ch.edu>
Acked-by: Adamson, Andy <William.Adamson@...app.com>
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 fs/nfs/nfs4filelayoutdev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/nfs4filelayoutdev.c b/fs/nfs/nfs4filelayoutdev.c
index efac602edb37..91de91430b31 100644
--- a/fs/nfs/nfs4filelayoutdev.c
+++ b/fs/nfs/nfs4filelayoutdev.c
@@ -827,7 +827,8 @@ nfs4_fl_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx)
 		nfs4_wait_ds_connect(ds);
 	}
 out_test_devid:
-	if (filelayout_test_devid_unavailable(devid))
+	if (ret->ds_clp == NULL ||
+	    filelayout_test_devid_unavailable(devid))
 		ret = NULL;
 out:
 	return ret;
-- 
2.11.0