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Code Issues Releases Wiki Activity

Improve readability of copy_tree

Browse source 
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_root_child (direct child of the root being cloning)
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@gmail.com>
Link: https://lore.kernel.org/r/20240606173912.99442-1-jemmywong512@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Jemmy 2024-06-07 01:39:12 +08:00 committed by Christian Brauner
parent d4f50ea957
commit deebbd505c
No known key found for this signature in database
GPG key ID: 91C61BC06578DCA2
1 changed files with 31 additions and 28 deletions
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59
fs/namespace.c
View file

@ -1966,69 +1966,72 @@ static bool mnt_ns_loop(struct dentry *dentry)
return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; 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) int flag)
{ {
struct mount *res, *p, *q, *r, *parent; struct mount *res, *src_parent, *src_root_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); return ERR_PTR(-EINVAL);
if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
return ERR_PTR(-EINVAL); return ERR_PTR(-EINVAL);
res = q = clone_mnt(mnt, dentry, flag); res = dst_mnt = clone_mnt(src_root, dentry, flag);
if (IS_ERR(q)) if (IS_ERR(dst_mnt))
return q; 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(src_root_child, &src_root->mnt_mounts, mnt_child) {
list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { if (!is_subdir(src_root_child->mnt_mountpoint, dentry))
struct mount *s;
if (!is_subdir(r->mnt_mountpoint, dentry))
continue; continue;
for (s = r; s; s = next_mnt(s, r)) { for (src_mnt = src_root_child; src_mnt;
src_mnt = next_mnt(src_mnt, src_root_child)) {
if (!(flag & CL_COPY_UNBINDABLE) && if (!(flag & CL_COPY_UNBINDABLE) &&
IS_MNT_UNBINDABLE(s)) { IS_MNT_UNBINDABLE(src_mnt)) {
if (s->mnt.mnt_flags & MNT_LOCKED) { if (src_mnt->mnt.mnt_flags & MNT_LOCKED) {
/* Both unbindable and locked. */ /* Both unbindable and locked. */
q = ERR_PTR(-EPERM); dst_mnt = ERR_PTR(-EPERM);
goto out; goto out;
} else { } else {
s = skip_mnt_tree(s); src_mnt = skip_mnt_tree(src_mnt);
continue; continue;
} }
} }
if (!(flag & CL_COPY_MNT_NS_FILE) && if (!(flag & CL_COPY_MNT_NS_FILE) &&
is_mnt_ns_file(s->mnt.mnt_root)) { is_mnt_ns_file(src_mnt->mnt.mnt_root)) {
s = skip_mnt_tree(s); src_mnt = skip_mnt_tree(src_mnt);
continue; continue;
} }
while (p != s->mnt_parent) { while (src_parent != src_mnt->mnt_parent) {
p = p->mnt_parent; src_parent = src_parent->mnt_parent;
q = q->mnt_parent; dst_mnt = dst_mnt->mnt_parent;
} }
p = s;
parent = q; src_parent = src_mnt;
q = clone_mnt(p, p->mnt.mnt_root, flag); dst_parent = dst_mnt;
if (IS_ERR(q)) dst_mnt = clone_mnt(src_mnt, src_mnt->mnt.mnt_root, flag);
if (IS_ERR(dst_mnt))
goto out; goto out;
lock_mount_hash(); lock_mount_hash();
list_add_tail(&q->mnt_list, &res->mnt_list); list_add_tail(&dst_mnt->mnt_list, &res->mnt_list);
attach_mnt(q, parent, p->mnt_mp, false); attach_mnt(dst_mnt, dst_parent, src_parent->mnt_mp, false);
unlock_mount_hash(); unlock_mount_hash();
} }
} }
return res; return res;
out: out:
if (res) { if (res) {
lock_mount_hash(); lock_mount_hash();
umount_tree(res, UMOUNT_SYNC); umount_tree(res, UMOUNT_SYNC);
unlock_mount_hash(); unlock_mount_hash();
} }
return q; return dst_mnt;
} }
/* Caller should check returned pointer for errors */ /* Caller should check returned pointer for errors */