If possible find the common ancestor of two dentries.
This is necessary infrastructure for better handling the case
when a dentry is moved out from under the root of a bind mount.
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
fs/dcache.c | 37 +++++++++++++++++++++++++++++++++++++
include/linux/dcache.h | 1 +
2 files changed, 38 insertions(+)
diff --git a/fs/dcache.c b/fs/dcache.c
index c1eece74621f..1f2f51055515 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2469,6 +2469,43 @@ void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
}
EXPORT_SYMBOL(dentry_update_name_case);
+static unsigned long d_depth(const struct dentry *dentry)
+{
+ unsigned long depth = 0;
+
+ while (!IS_ROOT(dentry)) {
+ dentry = dentry->d_parent;
+ depth++;
+ }
+ return depth;
+}
+
+const struct dentry *d_common_ancestor(const struct dentry *left,
+ const struct dentry *right)
+{
+ unsigned long ldepth = d_depth(left);
+ unsigned long rdepth = d_depth(right);
+
+ while (ldepth > rdepth) {
+ left = left->d_parent;
+ ldepth--;
+ }
+
+ while (rdepth > ldepth) {
+ right = right->d_parent;
+ rdepth--;
+ }
+
+ while (left != right) {
+ if (IS_ROOT(left))
+ return NULL;
+ left = left->d_parent;
+ right = right->d_parent;
+ }
+
+ return left;
+}
+
static void swap_names(struct dentry *dentry, struct dentry *target)
{
if (unlikely(dname_external(target))) {
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 06bed2a1053c..5b69856b45a2 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -313,6 +313,7 @@ extern void dentry_update_name_case(struct dentry *, struct qstr *);
extern void d_move(struct dentry *, struct dentry *);
extern void d_exchange(struct dentry *, struct dentry *);
extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
+extern const struct dentry *d_common_ancestor(const struct dentry *, const struct dentry *);
/* appendix may either be NULL or be used for transname suffixes */
extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
--
2.2.1
_______________________________________________
Containers mailing list
Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/containers
