nfs_common: fix localio to cope with racing nfs_local_probe()

Fix the possibility of racing nfs_local_probe() resulting in:
  list_add double add: new=ffff8b99707f9f58, prev=ffff8b99707f9f58, next=ffffffffc0f30000.
  ------------[ cut here ]------------
  kernel BUG at lib/list_debug.c:35!

Add nfs_uuid_init() to properly initialize all nfs_uuid_t members
(particularly its list_head).

Switch to returning bool from nfs_uuid_begin(), returns false if
nfs_uuid_t is already in-use (its list_head is on a list). Update
nfs_local_probe() to return early if the nfs_client's cl_uuid
(nfs_uuid_t) is in-use.

Also, switch nfs_uuid_begin() from using list_add_tail_rcu() to
list_add_tail() -- rculist was used in an earlier version of the
localio code that had a lockless nfs_uuid_lookup interface.

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/nfslocalio.h b/include/linux/nfslocalio.h
index b0dd9b1eef4f..3982fea79919 100644
--- a/include/linux/nfslocalio.h
+++ b/include/linux/nfslocalio.h
@@ -32,7 +32,8 @@ typedef struct {
 	struct auth_domain *dom; /* auth_domain for localio */
 } nfs_uuid_t;
 
-void nfs_uuid_begin(nfs_uuid_t *);
+void nfs_uuid_init(nfs_uuid_t *);
+bool nfs_uuid_begin(nfs_uuid_t *);
 void nfs_uuid_end(nfs_uuid_t *);
 void nfs_uuid_is_local(const uuid_t *, struct list_head *,
 		       struct net *, struct auth_domain *, struct module *);