NFSv4: fix delegated locking

Arnaud Giersch reports that NFSv4 locking is broken when we hold a
delegation since commit 8e469ebd6dc32cbaf620e134d79f740bf0ebab79 (NFSv4:
Don't allow posix locking against servers that don't support it).

According to Arnaud, the lock succeeds the first time he opens the file
(since we cannot do a delegated open) but then fails after we start using
delegated opens.

The following patch fixes it by ensuring that locking behaviour is
governed by a per-filesystem capability flag that is initially set, but
gets cleared if the server ever returns an OPEN without the
NFS4_OPEN_RESULT_LOCKTYPE_POSIX flag being set.

Reported-by: Arnaud Giersch <arnaud.giersch@iut-bm.univ-fcomte.fr>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org

3 files changed, 6 insertions, 2 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 2a3d352c0bff..a8766c4ef2e0 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -1294,7 +1294,8 @@ static int nfs4_init_server(struct nfs_server *server,
 
         /* Initialise the client representation from the mount data */
         server->flags = data->flags;
-        server->caps |= NFS_CAP_ATOMIC_OPEN|NFS_CAP_CHANGE_ATTR;
+        server->caps |= NFS_CAP_ATOMIC_OPEN|NFS_CAP_CHANGE_ATTR|
+                NFS_CAP_POSIX_LOCK;
         server->options = data->options;
 
         /* Get a client record */
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index fe0cd9eb1d4d..638067007c65 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1523,6 +1523,8 @@ static int _nfs4_proc_open(struct nfs4_opendata *data)
                 nfs_post_op_update_inode(dir, o_res->dir_attr);
         } else
                 nfs_refresh_inode(dir, o_res->dir_attr);
+        if ((o_res->rflags & NFS4_OPEN_RESULT_LOCKTYPE_POSIX) == 0)
+                server->caps &= ~NFS_CAP_POSIX_LOCK;
         if(o_res->rflags & NFS4_OPEN_RESULT_CONFIRM) {
                 status = _nfs4_proc_open_confirm(data);
                 if (status != 0)
@@ -1664,7 +1666,7 @@ static int _nfs4_do_open(struct inode *dir, struct path *path, fmode_t fmode, in
         status = PTR_ERR(state);
         if (IS_ERR(state))
                 goto err_opendata_put;
-        if ((opendata->o_res.rflags & NFS4_OPEN_RESULT_LOCKTYPE_POSIX) != 0)
+        if (server->caps & NFS_CAP_POSIX_LOCK)
                 set_bit(NFS_STATE_POSIX_LOCKS, &state->flags);
         nfs4_opendata_put(opendata);
         nfs4_put_state_owner(sp);
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 717a5e54eb1d..e82957acea56 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -176,6 +176,7 @@ struct nfs_server {
 #define NFS_CAP_ATIME           (1U << 11)
 #define NFS_CAP_CTIME           (1U << 12)
 #define NFS_CAP_MTIME           (1U << 13)
+#define NFS_CAP_POSIX_LOCK      (1U << 14)
 
 
 /* maximum number of slots to use */