vfs: add lookup_hash() helper
Overlayfs needs lookup without inode_permission() and already has the name
hash (in form of dentry->d_name on overlayfs dentry). It also doesn't
support filesystems with d_op->d_hash() so basically it only needs
the actual hashed lookup from lookup_one_len_unlocked()
So add a new helper that does unlocked lookup of a hashed name.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
diff --git a/fs/namei.c b/fs/namei.c
index 3ef87d6..1a1ea79 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2267,6 +2267,33 @@
EXPORT_SYMBOL(vfs_path_lookup);
/**
+ * lookup_hash - lookup single pathname component on already hashed name
+ * @name: name and hash to lookup
+ * @base: base directory to lookup from
+ *
+ * The name must have been verified and hashed (see lookup_one_len()). Using
+ * this after just full_name_hash() is unsafe.
+ *
+ * This function also doesn't check for search permission on base directory.
+ *
+ * Use lookup_one_len_unlocked() instead, unless you really know what you are
+ * doing.
+ *
+ * Do not hold i_mutex; this helper takes i_mutex if necessary.
+ */
+struct dentry *lookup_hash(const struct qstr *name, struct dentry *base)
+{
+ struct dentry *ret;
+
+ ret = lookup_dcache(name, base, 0);
+ if (!ret)
+ ret = lookup_slow(name, base, 0);
+
+ return ret;
+}
+EXPORT_SYMBOL(lookup_hash);
+
+/**
* lookup_one_len - filesystem helper to lookup single pathname component
* @name: pathname component to lookup
* @base: base directory to lookup from
@@ -2337,7 +2364,6 @@
struct qstr this;
unsigned int c;
int err;
- struct dentry *ret;
this.name = name;
this.len = len;
@@ -2369,10 +2395,7 @@
if (err)
return ERR_PTR(err);
- ret = lookup_dcache(&this, base, 0);
- if (!ret)
- ret = lookup_slow(&this, base, 0);
- return ret;
+ return lookup_hash(&this, base);
}
EXPORT_SYMBOL(lookup_one_len_unlocked);