Doesn't take much massage, and we no longer need to make sure that
by the time of final mntput() the victim has been removed from the
list. Makes life safer for ->d_automount() instances...
Rules:
* all ->mnt_expire accesses are under mount_lock.
* insertion into the list is done by mnt_set_expiry(), and
caller (->d_automount() instance) must hold a reference to mount
in question. It shouldn't be done more than once for a mount.
* if a mount on an expiry list is not yet mounted, it will
be ignored by anything that walks that list.
* if the final mntput() finds its victim still on an expiry
list (in which case it must've never been mounted - umount_tree()
would've taken it out), it will remove the victim from the list.
Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/namespace.c | 28 +++++++++++-----------------
1 file changed, 11 insertions(+), 17 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index c4aba4e096ae..164b80108cc4 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1353,13 +1353,6 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
list_add(&mnt->mnt_slave, &old->mnt_slave);
mnt->mnt_master = old->mnt_master;
}
-
- /* stick the duplicate mount on the same expiry list
- * as the original if that was on one */
- if (flag & CL_EXPIRE) {
- if (!list_empty(&old->mnt_expire))
- list_add(&mnt->mnt_expire, &old->mnt_expire);
- }
return mnt;
out_free:
@@ -1452,6 +1445,8 @@ static void mntput_no_expire(struct mount *mnt)
rcu_read_unlock();
list_del(&mnt->mnt_instance);
+ if (unlikely(!list_empty(&mnt->mnt_expire)))
+ list_del(&mnt->mnt_expire);
if (unlikely(!list_empty(&mnt->mnt_mounts))) {
struct mount *p, *tmp;
@@ -2273,6 +2268,13 @@ struct mount *copy_tree(struct mount *src_root, struct dentry *dentry,
lock_mount_hash();
if (src_mnt->mnt.mnt_flags & MNT_LOCKED)
dst_mnt->mnt.mnt_flags |= MNT_LOCKED;
+ if (unlikely(flag & CL_EXPIRE)) {
+ /* stick the duplicate mount on the same expiry
+ * list as the original if that was on one */
+ if (!list_empty(&src_mnt->mnt_expire))
+ list_add(&dst_mnt->mnt_expire,
+ &src_mnt->mnt_expire);
+ }
list_add_tail(&dst_mnt->mnt_list, &res->mnt_list);
attach_mnt(dst_mnt, dst_parent, src_parent->mnt_mp);
unlock_mount_hash();
@@ -3891,12 +3893,6 @@ int finish_automount(struct vfsmount *m, const struct path *path)
namespace_unlock();
inode_unlock(dentry->d_inode);
discard:
- /* remove m from any expiration list it may be on */
- if (!list_empty(&mnt->mnt_expire)) {
- namespace_lock();
- list_del_init(&mnt->mnt_expire);
- namespace_unlock();
- }
mntput(m);
return err;
}
@@ -3908,11 +3904,9 @@ int finish_automount(struct vfsmount *m, const struct path *path)
*/
void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
{
- namespace_lock();
-
+ read_seqlock_excl(&mount_lock);
list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
-
- namespace_unlock();
+ read_sequnlock_excl(&mount_lock);
}
EXPORT_SYMBOL(mnt_set_expiry);
--
2.39.5
