NFSv4: Ensure we reference the inode for return-on-close in delegreturn

If we have to do a return-on-close in the delegreturn code, then
we must ensure that the inode and super block remain referenced.

Cc: Peng Tao <tao.peng@primarydata.com>
Cc: stable@vger.kernel.org # 3.17.x
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: Peng Tao <tao.peng@primarydata.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 31a11b0e885d..368d9395d2e7 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -405,12 +405,15 @@ void __exit unregister_nfs_fs(void)
 	unregister_filesystem(&nfs_fs_type);
 }
 
-void nfs_sb_active(struct super_block *sb)
+bool nfs_sb_active(struct super_block *sb)
 {
 	struct nfs_server *server = NFS_SB(sb);
 
-	if (atomic_inc_return(&server->active) == 1)
-		atomic_inc(&sb->s_active);
+	if (!atomic_inc_not_zero(&sb->s_active))
+		return false;
+	if (atomic_inc_return(&server->active) != 1)
+		atomic_dec(&sb->s_active);
+	return true;
 }
 EXPORT_SYMBOL_GPL(nfs_sb_active);