NFSv4: Ensure delegation recall and byte range lock removal don't conflict

Add a mutex to the struct nfs4_state_owner to ensure that delegation
recall doesn't conflict with byte range lock removal.

Note that we nest the new mutex _outside_ the state manager reclaim
protection (nfsi->rwsem) in order to avoid deadlocks.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index f7e05ade5572..d51227371c67 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4485,7 +4485,9 @@ static struct rpc_task *nfs4_do_unlck(struct file_lock *fl,
 
 static int nfs4_proc_unlck(struct nfs4_state *state, int cmd, struct file_lock *request)
 {
-        struct nfs_inode *nfsi = NFS_I(state->inode);
+        struct inode *inode = state->inode;
+        struct nfs4_state_owner *sp = state->owner;
+        struct nfs_inode *nfsi = NFS_I(inode);
         struct nfs_seqid *seqid;
         struct nfs4_lock_state *lsp;
         struct rpc_task *task;
@@ -4495,12 +4497,17 @@ static int nfs4_proc_unlck(struct nfs4_state *state, int cmd, struct file_lock *
         status = nfs4_set_lock_state(state, request);
         /* Unlock _before_ we do the RPC call */
         request->fl_flags |= FL_EXISTS;
+        /* Exclude nfs_delegation_claim_locks() */
+        mutex_lock(&sp->so_delegreturn_mutex);
+        /* Exclude nfs4_reclaim_open_stateid() - note nesting! */
         down_read(&nfsi->rwsem);
         if (do_vfs_lock(request->fl_file, request) == -ENOENT) {
                 up_read(&nfsi->rwsem);
+                mutex_unlock(&sp->so_delegreturn_mutex);
                 goto out;
         }
         up_read(&nfsi->rwsem);
+        mutex_unlock(&sp->so_delegreturn_mutex);
         if (status != 0)
                 goto out;
         /* Is this a delegated lock? */