kernfs: implement kernfs_walk_and_get()
Implement kernfs_walk_and_get() which is similar to
kernfs_find_and_get() but can walk a path instead of just a name.
v2: Use strlcpy() instead of strlen() + memcpy() as suggested by
David.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: David Miller <davem@davemloft.net>
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 91e0045..742bf4a 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -694,6 +694,29 @@
return NULL;
}
+static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
+ const unsigned char *path,
+ const void *ns)
+{
+ static char path_buf[PATH_MAX]; /* protected by kernfs_mutex */
+ size_t len = strlcpy(path_buf, path, PATH_MAX);
+ char *p = path_buf;
+ char *name;
+
+ lockdep_assert_held(&kernfs_mutex);
+
+ if (len >= PATH_MAX)
+ return NULL;
+
+ while ((name = strsep(&p, "/")) && parent) {
+ if (*name == '\0')
+ continue;
+ parent = kernfs_find_ns(parent, name, ns);
+ }
+
+ return parent;
+}
+
/**
* kernfs_find_and_get_ns - find and get kernfs_node with the given name
* @parent: kernfs_node to search under
@@ -719,6 +742,29 @@
EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
/**
+ * kernfs_walk_and_get_ns - find and get kernfs_node with the given path
+ * @parent: kernfs_node to search under
+ * @path: path to look for
+ * @ns: the namespace tag to use
+ *
+ * Look for kernfs_node with path @path under @parent and get a reference
+ * if found. This function may sleep and returns pointer to the found
+ * kernfs_node on success, %NULL on failure.
+ */
+struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
+ const char *path, const void *ns)
+{
+ struct kernfs_node *kn;
+
+ mutex_lock(&kernfs_mutex);
+ kn = kernfs_walk_ns(parent, path, ns);
+ kernfs_get(kn);
+ mutex_unlock(&kernfs_mutex);
+
+ return kn;
+}
+
+/**
* kernfs_create_root - create a new kernfs hierarchy
* @scops: optional syscall operations for the hierarchy
* @flags: KERNFS_ROOT_* flags
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 5d4e9c4..af51df3 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -274,6 +274,8 @@
struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
const char *name, const void *ns);
+struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
+ const char *path, const void *ns);
void kernfs_get(struct kernfs_node *kn);
void kernfs_put(struct kernfs_node *kn);
@@ -350,6 +352,10 @@
kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
const void *ns)
{ return NULL; }
+static inline struct kernfs_node *
+kernfs_walk_and_get_ns(struct kernfs_node *parent, const char *path,
+ const void *ns)
+{ return NULL; }
static inline void kernfs_get(struct kernfs_node *kn) { }
static inline void kernfs_put(struct kernfs_node *kn) { }
@@ -431,6 +437,12 @@
}
static inline struct kernfs_node *
+kernfs_walk_and_get(struct kernfs_node *kn, const char *path)
+{
+ return kernfs_walk_and_get_ns(kn, path, NULL);
+}
+
+static inline struct kernfs_node *
kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
void *priv)
{
