On Thu 06-06-24 17:02:54, Jemmy wrote:
> by employing `copy mount tree from src to dst` concept.
> This involves renaming the opaque variables (e.g., p, q, r, s)
> to be more descriptive, aiming to make the code easier to understand.
>
> Changes:
> mnt -> src_root (root of the tree to copy)
> r -> src_child (direct child of the root being cloning)
I'd call this src_root_child to distinguish it from a child of
"src_parent". Otherwise these names work for me.
> p -> src_parent (parent of src_mnt)
> s -> src_mnt (current mount being copying)
> parent -> dst_parent (parent of dst_child)
> q -> dst_mnt (freshly cloned mount)
>
> Signed-off-by: Jemmy <jemmywong512@xxxxxxxxx>
Honza
> ---
> fs/namespace.c | 59 ++++++++++++++++++++++++++------------------------
> 1 file changed, 31 insertions(+), 28 deletions(-)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 5a51315c6678..0dd43633607b 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -1966,69 +1966,72 @@ static bool mnt_ns_loop(struct dentry *dentry)
> return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
> }
>
> -struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
> +struct mount *copy_tree(struct mount *src_root, struct dentry *dentry,
> int flag)
> {
> - struct mount *res, *p, *q, *r, *parent;
> + struct mount *res, *src_parent, *src_child, *src_mnt,
> + *dst_parent, *dst_mnt;
>
> - if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
> + if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(src_root))
> return ERR_PTR(-EINVAL);
>
> if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
> return ERR_PTR(-EINVAL);
>
> - res = q = clone_mnt(mnt, dentry, flag);
> - if (IS_ERR(q))
> - return q;
> + res = dst_mnt = clone_mnt(src_root, dentry, flag);
> + if (IS_ERR(dst_mnt))
> + return dst_mnt;
>
> - q->mnt_mountpoint = mnt->mnt_mountpoint;
> + src_parent = src_root;
> + dst_mnt->mnt_mountpoint = src_root->mnt_mountpoint;
>
> - p = mnt;
> - list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
> - struct mount *s;
> - if (!is_subdir(r->mnt_mountpoint, dentry))
> + list_for_each_entry(src_child, &src_root->mnt_mounts, mnt_child) {
> + if (!is_subdir(src_child->mnt_mountpoint, dentry))
> continue;
>
> - for (s = r; s; s = next_mnt(s, r)) {
> + for (src_mnt = src_child; src_mnt;
> + src_mnt = next_mnt(src_mnt, src_child)) {
> if (!(flag & CL_COPY_UNBINDABLE) &&
> - IS_MNT_UNBINDABLE(s)) {
> - if (s->mnt.mnt_flags & MNT_LOCKED) {
> + IS_MNT_UNBINDABLE(src_mnt)) {
> + if (src_mnt->mnt.mnt_flags & MNT_LOCKED) {
> /* Both unbindable and locked. */
> - q = ERR_PTR(-EPERM);
> + dst_mnt = ERR_PTR(-EPERM);
> goto out;
> } else {
> - s = skip_mnt_tree(s);
> + src_mnt = skip_mnt_tree(src_mnt);
> continue;
> }
> }
> if (!(flag & CL_COPY_MNT_NS_FILE) &&
> - is_mnt_ns_file(s->mnt.mnt_root)) {
> - s = skip_mnt_tree(s);
> + is_mnt_ns_file(src_mnt->mnt.mnt_root)) {
> + src_mnt = skip_mnt_tree(src_mnt);
> continue;
> }
> - while (p != s->mnt_parent) {
> - p = p->mnt_parent;
> - q = q->mnt_parent;
> + while (src_parent != src_mnt->mnt_parent) {
> + src_parent = src_parent->mnt_parent;
> + dst_mnt = dst_mnt->mnt_parent;
> }
> - p = s;
> - parent = q;
> - q = clone_mnt(p, p->mnt.mnt_root, flag);
> - if (IS_ERR(q))
> +
> + src_parent = src_mnt;
> + dst_parent = dst_mnt;
> + dst_mnt = clone_mnt(src_mnt, src_mnt->mnt.mnt_root, flag);
> + if (IS_ERR(dst_mnt))
> goto out;
> lock_mount_hash();
> - list_add_tail(&q->mnt_list, &res->mnt_list);
> - attach_mnt(q, parent, p->mnt_mp, false);
> + list_add_tail(&dst_mnt->mnt_list, &res->mnt_list);
> + attach_mnt(dst_mnt, dst_parent, src_parent->mnt_mp, false);
> unlock_mount_hash();
> }
> }
> return res;
> +
> out:
> if (res) {
> lock_mount_hash();
> umount_tree(res, UMOUNT_SYNC);
> unlock_mount_hash();
> }
> - return q;
> + return dst_mnt;
> }
>
> /* Caller should check returned pointer for errors */
> --
> 2.34.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
