[PATCH 4/5] kernfs: implement kernfs_path_len()

From: Tejun Heo
Date: Tue Jul 07 2015 - 11:11:54 EST


Add a function to determine the path length of a kernfs node. This
for now will be used by writeback tracepoint updates.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/kernfs/dir.c | 23 +++++++++++++++++++++++
include/linux/kernfs.h | 4 ++++
2 files changed, 27 insertions(+)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 2d48d28..91e0045 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -92,6 +92,29 @@ int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
}

/**
+ * kernfs_path_len - determine the length of the full path of a given node
+ * @kn: kernfs_node of interest
+ *
+ * The returned length doesn't include the space for the terminating '\0'.
+ */
+size_t kernfs_path_len(struct kernfs_node *kn)
+{
+ size_t len = 0;
+ unsigned long flags;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+
+ do {
+ len += strlen(kn->name) + 1;
+ kn = kn->parent;
+ } while (kn && kn->parent);
+
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+
+ return len;
+}
+
+/**
* kernfs_path - build full path of a given node
* @kn: kernfs_node of interest
* @buf: buffer to copy @kn's name into
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 123be25..5d4e9c4 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -266,6 +266,7 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
}

int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
+size_t kernfs_path_len(struct kernfs_node *kn);
char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
size_t buflen);
void pr_cont_kernfs_name(struct kernfs_node *kn);
@@ -332,6 +333,9 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
{ return -ENOSYS; }

+static inline size_t kernfs_path_len(struct kernfs_node *kn)
+{ return 0; }
+
static inline char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
size_t buflen)
{ return NULL; }
--
2.4.3

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