diff mbox

[2/8] kernfs: implement kernfs_walk_and_get()

Message ID 1449527935-27056-3-git-send-email-tj@kernel.org
State Awaiting Upstream
Delegated to: Pablo Neira
Headers show

Commit Message

Tejun Heo Dec. 7, 2015, 10:38 p.m. UTC 
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>
---
 fs/kernfs/dir.c        | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/kernfs.h | 12 ++++++++++++
 2 files changed, 58 insertions(+)

Comments

Geert Uytterhoeven Jan. 15, 2016, 12:29 p.m. UTC | #1 
On Mon, Dec 7, 2015 at 11:38 PM, Tejun Heo <tj@kernel.org> wrote:
> 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>
> ---
>  fs/kernfs/dir.c        | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/kernfs.h | 12 ++++++++++++
>  2 files changed, 58 insertions(+)
>
> 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 @@ static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
>         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 */

This is showing up in bloat-o-meter as increasing kernel size by 4 KiB.

> +       size_t len = strlcpy(path_buf, path, PATH_MAX);

The full input string is copied because strsep() replaces the delimiters by
zeroes?
Can this be handled in some other way?

> +       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;
> +}

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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diff mbox

Patch

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 @@  static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
 	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 @@  struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
 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 @@  void pr_cont_kernfs_path(struct kernfs_node *kn);
 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 @@  static inline struct kernfs_node *
 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 @@  kernfs_find_and_get(struct kernfs_node *kn, const char *name)
 }
 
 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)
 {