[RFC][PATCH 1/3] vfs: Keep a list of mounts on a mount point

[Eric W. Biederman]

Signed-off-by: Eric W. Biederman <ebieder...@twitter.com>
---
 fs/mount.h     |    2 ++
 fs/namespace.c |    5 +++++
 2 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/fs/mount.h b/fs/mount.h
index 64a858143ff9..e4342b8dfab1 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -21,6 +21,7 @@ struct mnt_pcp {
 struct mountpoint {
        struct list_head m_hash;
        struct dentry *m_dentry;
+       struct list_head m_list;
        int m_count;
 };
 
@@ -47,6 +48,7 @@ struct mount {
        struct mount *mnt_master;       /* slave is on master->mnt_slave_list */
        struct mnt_namespace *mnt_ns;   /* containing namespace */
        struct mountpoint *mnt_mp;      /* where is it mounted */
+       struct list_head mnt_mp_list;   /* list mounts with the same mountpoint 
*/
 #ifdef CONFIG_FSNOTIFY
        struct hlist_head mnt_fsnotify_marks;
        __u32 mnt_fsnotify_mask;
diff --git a/fs/namespace.c b/fs/namespace.c
index da5c49483430..d092964fe7f9 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -197,6 +197,7 @@ static struct mount *alloc_vfsmnt(const char *name)
                INIT_LIST_HEAD(&mnt->mnt_share);
                INIT_LIST_HEAD(&mnt->mnt_slave_list);
                INIT_LIST_HEAD(&mnt->mnt_slave);
+               INIT_LIST_HEAD(&mnt->mnt_mp_list);
 #ifdef CONFIG_FSNOTIFY
                INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
 #endif
@@ -636,6 +637,7 @@ static struct mountpoint *new_mountpoint(struct dentry 
*dentry)
        mp->m_dentry = dentry;
        mp->m_count = 1;
        list_add(&mp->m_hash, chain);
+       INIT_LIST_HEAD(&mp->m_list);
        return mp;
 }
 
@@ -691,6 +693,7 @@ static void detach_mnt(struct mount *mnt, struct path 
*old_path)
        list_del_init(&mnt->mnt_hash);
        put_mountpoint(mnt->mnt_mp);
        mnt->mnt_mp = NULL;
+       list_del_init(&mnt->mnt_mp_list);
 }
 
 /*
@@ -705,6 +708,7 @@ void mnt_set_mountpoint(struct mount *mnt,
        child_mnt->mnt_mountpoint = dget(mp->m_dentry);
        child_mnt->mnt_parent = mnt;
        child_mnt->mnt_mp = mp;
+       list_add_tail(&child_mnt->mnt_mp_list, &mp->m_list);
 }
 
 /*
@@ -1193,6 +1197,7 @@ void umount_tree(struct mount *mnt, int propagate)
                        p->mnt_parent->mnt_ghosts++;
                        put_mountpoint(p->mnt_mp);
                        p->mnt_mp = NULL;
+                       list_del_init(&mnt->mnt_mp_list);
                }
                change_mnt_propagation(p, MS_PRIVATE);
        }
-- 
1.7.5.4

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