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authorRam Pai <linuxram@us.ibm.com>2005-11-07 17:20:17 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2005-11-07 18:18:11 -0800
commita05964f3917c7c55368c229d7985f8e7c9977e97 (patch)
tree7ec25550267ef050572c00ba2f37d6a4ff9c469e /fs/pnode.c
parent2144440327fa01b2f3f65e355120a78211685702 (diff)
downloadlinux-linaro-a05964f3917c7c55368c229d7985f8e7c9977e97.tar.gz
[PATCH] shared mounts handling: umount
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>
Diffstat (limited to 'fs/pnode.c')
-rw-r--r--fs/pnode.c87
1 files changed, 86 insertions, 1 deletions
diff --git a/fs/pnode.c b/fs/pnode.c
index 2d572b88e6f..7bc942d047c 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -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;
+}