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    Subject[PATCH 4.0 109/220] mnt: In umount_tree reuse mnt_list instead of mnt_hash
    Date
    4.0-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: "Eric W. Biederman" <ebiederm@xmission.com>

    commit c003b26ff98ca04a180ff34c38c007a3998d62f9 upstream.

    umount_tree builds a list of mounts that need to be unmounted.
    Utilize mnt_list for this purpose instead of mnt_hash. This begins to
    allow keeping a mount on the mnt_hash after it is unmounted, which is
    necessary for a properly functioning MNT_LOCKED implementation.

    The fact that mnt_list is an ordinary list makding available list_move
    is nice bonus.

    Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/namespace.c | 20 +++++++++++---------
    fs/pnode.c | 6 +++---
    fs/pnode.h | 2 +-
    3 files changed, 15 insertions(+), 13 deletions(-)

    --- a/fs/namespace.c
    +++ b/fs/namespace.c
    @@ -1329,23 +1329,25 @@ enum umount_tree_flags {
    */
    static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
    {
    - HLIST_HEAD(tmp_list);
    + LIST_HEAD(tmp_list);
    struct mount *p;

    - for (p = mnt; p; p = next_mnt(p, mnt)) {
    - hlist_del_init_rcu(&p->mnt_hash);
    - hlist_add_head(&p->mnt_hash, &tmp_list);
    - }
    + /* Gather the mounts to umount */
    + for (p = mnt; p; p = next_mnt(p, mnt))
    + list_move(&p->mnt_list, &tmp_list);

    - hlist_for_each_entry(p, &tmp_list, mnt_hash)
    + /* Hide the mounts from lookup_mnt and mnt_mounts */
    + list_for_each_entry(p, &tmp_list, mnt_list) {
    + hlist_del_init_rcu(&p->mnt_hash);
    list_del_init(&p->mnt_child);
    + }

    + /* Add propogated mounts to the tmp_list */
    if (how & UMOUNT_PROPAGATE)
    propagate_umount(&tmp_list);

    - while (!hlist_empty(&tmp_list)) {
    - p = hlist_entry(tmp_list.first, struct mount, mnt_hash);
    - hlist_del_init_rcu(&p->mnt_hash);
    + while (!list_empty(&tmp_list)) {
    + p = list_first_entry(&tmp_list, struct mount, mnt_list);
    list_del_init(&p->mnt_expire);
    list_del_init(&p->mnt_list);
    __touch_mnt_namespace(p->mnt_ns);
    --- a/fs/pnode.c
    +++ b/fs/pnode.c
    @@ -384,7 +384,7 @@ static void __propagate_umount(struct mo
    if (child && list_empty(&child->mnt_mounts)) {
    list_del_init(&child->mnt_child);
    hlist_del_init_rcu(&child->mnt_hash);
    - hlist_add_before_rcu(&child->mnt_hash, &mnt->mnt_hash);
    + list_move_tail(&child->mnt_list, &mnt->mnt_list);
    }
    }
    }
    @@ -396,11 +396,11 @@ static void __propagate_umount(struct mo
    *
    * vfsmount lock must be held for write
    */
    -int propagate_umount(struct hlist_head *list)
    +int propagate_umount(struct list_head *list)
    {
    struct mount *mnt;

    - hlist_for_each_entry(mnt, list, mnt_hash)
    + list_for_each_entry(mnt, list, mnt_list)
    __propagate_umount(mnt);
    return 0;
    }
    --- a/fs/pnode.h
    +++ b/fs/pnode.h
    @@ -40,7 +40,7 @@ static inline void set_mnt_shared(struct
    void change_mnt_propagation(struct mount *, int);
    int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,
    struct hlist_head *);
    -int propagate_umount(struct hlist_head *);
    +int propagate_umount(struct list_head *);
    int propagate_mount_busy(struct mount *, int);
    void mnt_release_group_id(struct mount *);
    int get_dominating_id(struct mount *mnt, const struct path *root);



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