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[PATCH] shared mounts handling: umount

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An unmount of a mount creates a umount event on the parent.  If the
parent is a shared mount, it gets propagated to all mounts in the peer
group.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Ram Pai 2005-11-07 17:20:17 -05:00 • committed by Linus Torvalds
parent 2144440327
commit a05964f391
5 changed files with 128 additions and 20 deletions
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87
fs/pnode.c
View file

@ -99,9 +99,94 @@ out:
while (!list_empty(&tmp_list)) {
child = list_entry(tmp_list.next, struct vfsmount, mnt_hash);
list_del_init(&child->mnt_hash);
umount_tree(child, &umount_list);
umount_tree(child, 0, &umount_list);
}
spin_unlock(&vfsmount_lock);
release_mounts(&umount_list);
return ret;
}
/*
* return true if the refcount is greater than count
*/
static inline int do_refcount_check(struct vfsmount *mnt, int count)
{
int mycount = atomic_read(&mnt->mnt_count);
return (mycount > count);
}
/*
* check if the mount 'mnt' can be unmounted successfully.
* @mnt: the mount to be checked for unmount
* NOTE: unmounting 'mnt' would naturally propagate to all
* other mounts its parent propagates to.
* Check if any of these mounts that **do not have submounts**
* have more references than 'refcnt'. If so return busy.
*/
int propagate_mount_busy(struct vfsmount *mnt, int refcnt)
{
struct vfsmount *m, *child;
struct vfsmount *parent = mnt->mnt_parent;
int ret = 0;
if (mnt == parent)
return do_refcount_check(mnt, refcnt);
/*
* quickly check if the current mount can be unmounted.
* If not, we don't have to go checking for all other
* mounts
*/
if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
return 1;
for (m = propagation_next(parent, parent); m;
m = propagation_next(m, parent)) {
child = __lookup_mnt(m, mnt->mnt_mountpoint, 0);
if (child && list_empty(&child->mnt_mounts) &&
(ret = do_refcount_check(child, 1)))
break;
}
return ret;
}
/*
* NOTE: unmounting 'mnt' naturally propagates to all other mounts its
* parent propagates to.
*/
static void __propagate_umount(struct vfsmount *mnt)
{
struct vfsmount *parent = mnt->mnt_parent;
struct vfsmount *m;
BUG_ON(parent == mnt);
for (m = propagation_next(parent, parent); m;
m = propagation_next(m, parent)) {
struct vfsmount *child = __lookup_mnt(m,
mnt->mnt_mountpoint, 0);
/*
* umount the child only if the child has no
* other children
*/
if (child && list_empty(&child->mnt_mounts)) {
list_del(&child->mnt_hash);
list_add_tail(&child->mnt_hash, &mnt->mnt_hash);
}
}
}
/*
* collect all mounts that receive propagation from the mount in @list,
* and return these additional mounts in the same list.
* @list: the list of mounts to be unmounted.
*/
int propagate_umount(struct list_head *list)
{
struct vfsmount *mnt;
list_for_each_entry(mnt, list, mnt_hash)
__propagate_umount(mnt);
return 0;
}