linux-kernel - [PATCH 3.10 089/250] NFSv4.1: nfs4_fl_prepare_ds must be careful about reporting success.

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Message-Id: <1496876436-32402-90-git-send-email-w@1wt.eu>
Date:   Thu,  8 Jun 2017 00:57:55 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     NeilBrown <neilb@...e.com>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 089/250] NFSv4.1: nfs4_fl_prepare_ds must be careful about reporting success.

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

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: Willy Tarreau <w@....eu>
---
 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 678cb89..b906d8e 100644
--- a/fs/nfs/nfs4filelayoutdev.c
+++ b/fs/nfs/nfs4filelayoutdev.c
@@ -821,7 +821,8 @@ 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;
-- 
2.8.0.rc2.1.gbe9624a