diff options
Diffstat (limited to 'fs/pnode.c')
| -rw-r--r-- | fs/pnode.c | 42 |
1 files changed, 41 insertions, 1 deletions
diff --git a/fs/pnode.c b/fs/pnode.c index 3cede8b18c8b..e4d0340393d5 100644 --- a/fs/pnode.c +++ b/fs/pnode.c @@ -216,7 +216,7 @@ static struct mount *next_group(struct mount *m, struct mount *origin) static struct mount *last_dest, *first_source, *last_source, *dest_master; static struct hlist_head *list; -static inline bool peers(struct mount *m1, struct mount *m2) +static inline bool peers(const struct mount *m1, const struct mount *m2) { return m1->mnt_group_id == m2->mnt_group_id && m1->mnt_group_id; } @@ -354,6 +354,46 @@ static inline int do_refcount_check(struct mount *mnt, int count) return mnt_get_count(mnt) > count; } +/** + * propagation_would_overmount - check whether propagation from @from + * would overmount @to + * @from: shared mount + * @to: mount to check + * @mp: future mountpoint of @to on @from + * + * If @from propagates mounts to @to, @from and @to must either be peers + * or one of the masters in the hierarchy of masters of @to must be a + * peer of @from. + * + * If the root of the @to mount is equal to the future mountpoint @mp of + * the @to mount on @from then @to will be overmounted by whatever is + * propagated to it. + * + * Context: This function expects namespace_lock() to be held and that + * @mp is stable. + * Return: If @from overmounts @to, true is returned, false if not. + */ +bool propagation_would_overmount(const struct mount *from, + const struct mount *to, + const struct mountpoint *mp) +{ + if (!IS_MNT_SHARED(from)) + return false; + + if (IS_MNT_NEW(to)) + return false; + + if (to->mnt.mnt_root != mp->m_dentry) + return false; + + for (const struct mount *m = to; m; m = m->mnt_master) { + if (peers(from, m)) + return true; + } + + return false; +} + /* * check if the mount 'mnt' can be unmounted successfully. * @mnt: the mount to be checked for unmount |