NFS: Fix a umount race

commit 387c149b54b4321cbc790dadbd4f8eedb5a90468 upstream.

Ensure that we unregister the bdi before kill_anon_super() calls
ida_remove() on our device name.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index e71f0fdff1dafb4e5ae9b22489ee35fe14bbf2ce..4bf23f6f93cf7b72833e4c2a6872e46ba6c15da6 100644 (file)
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -241,6 +241,7 @@ static int  nfs_show_stats(struct seq_file *, struct vfsmount *);
 static int nfs_get_sb(struct file_system_type *, int, const char *, void *, struct vfsmount *);
 static int nfs_xdev_get_sb(struct file_system_type *fs_type,
                int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
+static void nfs_put_super(struct super_block *);
 static void nfs_kill_super(struct super_block *);
 static int nfs_remount(struct super_block *sb, int *flags, char *raw_data);
 
@@ -264,6 +265,7 @@ static const struct super_operations nfs_sops = {
        .alloc_inode    = nfs_alloc_inode,
        .destroy_inode  = nfs_destroy_inode,
        .write_inode    = nfs_write_inode,
+       .put_super      = nfs_put_super,
        .statfs         = nfs_statfs,
        .clear_inode    = nfs_clear_inode,
        .umount_begin   = nfs_umount_begin,
@@ -333,6 +335,7 @@ static const struct super_operations nfs4_sops = {
        .alloc_inode    = nfs_alloc_inode,
        .destroy_inode  = nfs_destroy_inode,
        .write_inode    = nfs_write_inode,
+       .put_super      = nfs_put_super,
        .statfs         = nfs_statfs,
        .clear_inode    = nfs4_clear_inode,
        .umount_begin   = nfs_umount_begin,
@@ -2195,6 +2198,17 @@ error_splat_super:
        goto out;
 }
 
+/*
+ * Ensure that we unregister the bdi before kill_anon_super
+ * releases the device name
+ */
+static void nfs_put_super(struct super_block *s)
+{
+       struct nfs_server *server = NFS_SB(s);
+
+       bdi_unregister(&server->backing_dev_info);
+}
+
 /*
  * Destroy an NFS2/3 superblock
  */
@@ -2203,7 +2217,6 @@ static void nfs_kill_super(struct super_block *s)
        struct nfs_server *server = NFS_SB(s);
 
        kill_anon_super(s);
-       bdi_unregister(&server->backing_dev_info);
        nfs_fscache_release_super_cookie(s);
        nfs_free_server(server);
 }