Introduce a dentry revalidation helper to be used by case-insensitive
filesystems to check if it is safe to reuse a negative dentry.
A negative dentry is safe to be reused on a case-insensitive lookup if
it was created during a case-insensitive lookup and this is not a lookup
that will instantiate a dentry. If this is a creation lookup, we also
need to make sure the name matches sensitively the name under lookup in
order to assure the name preserving semantics.
Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
---
fs/libfs.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/fs/libfs.c b/fs/libfs.c
index 31b0ddf01c31..de43f3f585f1 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1450,9 +1450,33 @@ static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
return 0;
}
+static inline int generic_ci_d_revalidate(struct dentry *dentry,
+ const struct qstr *name,
+ unsigned int flags)
+{
+ int is_creation = flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET);
+
+ if (d_is_negative(dentry)) {
+ const struct dentry *parent = READ_ONCE(dentry->d_parent);
+ const struct inode *dir = READ_ONCE(parent->d_inode);
+
+ if (dir && needs_casefold(dir)) {
+ if (!d_is_casefold_lookup(dentry))
+ return 0;
+
+ if (is_creation &&
+ (dentry->d_name.len != name->len ||
+ memcmp(dentry->d_name.name, name->name, name->len)))
+ return 0;
+ }
+ }
+ return 1;
+}
+
static const struct dentry_operations generic_ci_dentry_ops = {
.d_hash = generic_ci_d_hash,
.d_compare = generic_ci_d_compare,
+ .d_revalidate_name = generic_ci_d_revalidate,
};
#endif
--
2.36.1
