vfs: keep list of mounts for each superblock

Keep track of vfsmounts belonging to a superblock.  List is protected
by vfsmount_lock.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index db65e2e4921f..145217b088d1 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -671,6 +671,9 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
         mnt->mnt.mnt_sb = root->d_sb;
         mnt->mnt_mountpoint = mnt->mnt.mnt_root;
         mnt->mnt_parent = mnt;
+        br_write_lock(vfsmount_lock);
+        list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
+        br_write_unlock(vfsmount_lock);
         return &mnt->mnt;
 }
 EXPORT_SYMBOL_GPL(vfs_kern_mount);
@@ -699,6 +702,9 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
                 mnt->mnt.mnt_root = dget(root);
                 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
                 mnt->mnt_parent = mnt;
+                br_write_lock(vfsmount_lock);
+                list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
+                br_write_unlock(vfsmount_lock);
 
                 if (flag & CL_SLAVE) {
                         list_add(&mnt->mnt_slave, &old->mnt_slave_list);
@@ -781,6 +787,7 @@ put_again:
                 acct_auto_close_mnt(&mnt->mnt);
                 goto put_again;
         }
+        list_del(&mnt->mnt_instance);
         br_write_unlock(vfsmount_lock);
         mntfree(mnt);
 }