[PATCH] NFSv4.1: nfs4_fl_prepare_ds must be careful about reporting success.

[NeilBrown <neilb@suse.com>]

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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@suse.com>
---
 fs/nfs/filelayout/filelayoutdev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/filelayout/filelayoutdev.c b/fs/nfs/filelayout/filelayoutdev.c
index 4946ef40ba87..85ef38f9765f 100644
--- a/fs/nfs/filelayout/filelayoutdev.c
+++ b/fs/nfs/filelayout/filelayoutdev.c
@@ -283,7 +283,8 @@ nfs4_fl_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx)
 			     s->nfs_client->cl_rpcclient->cl_auth->au_flavor);
 
 out_test_devid:
-	if (filelayout_test_devid_unavailable(devid))
+	if (ret->ds_clp == NULL ||
+	    filelayout_test_devid_unavailable(devid))
 		ret = NULL;
 out:
 	return ret;
-- 
2.10.1


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