NFSv4: Pin the superblock while we're returning the delegation

This patch ensures that the superblock doesn't go ahead and disappear
underneath us while the state manager thread is returning delegations.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 5ca502b5f877..be313e791e67 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -474,14 +474,20 @@ restart:
                                                                 super_list) {
                         if (!nfs_delegation_need_return(delegation))
                                 continue;
-                        inode = nfs_delegation_grab_inode(delegation);
-                        if (inode == NULL)
+                        if (!nfs_sb_active(server->super))
                                 continue;
+                        inode = nfs_delegation_grab_inode(delegation);
+                        if (inode == NULL) {
+                                rcu_read_unlock();
+                                nfs_sb_deactive(server->super);
+                                goto restart;
+                        }
                         delegation = nfs_start_delegation_return_locked(NFS_I(inode));
                         rcu_read_unlock();
 
                         err = nfs_end_delegation_return(inode, delegation, 0);
                         iput(inode);
+                        nfs_sb_deactive(server->super);
                         if (!err)
                                 goto restart;
                         set_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state);
@@ -815,9 +821,14 @@ restart:
                         if (test_bit(NFS_DELEGATION_NEED_RECLAIM,
                                                 &delegation->flags) == 0)
                                 continue;
-                        inode = nfs_delegation_grab_inode(delegation);
-                        if (inode == NULL)
+                        if (!nfs_sb_active(server->super))
                                 continue;
+                        inode = nfs_delegation_grab_inode(delegation);
+                        if (inode == NULL) {
+                                rcu_read_unlock();
+                                nfs_sb_deactive(server->super);
+                                goto restart;
+                        }
                         delegation = nfs_start_delegation_return_locked(NFS_I(inode));
                         rcu_read_unlock();
                         if (delegation != NULL) {
@@ -827,6 +838,7 @@ restart:
                                         nfs_free_delegation(delegation);
                         }
                         iput(inode);
+                        nfs_sb_deactive(server->super);
                         goto restart;
                 }
         }