Merge branch 'for-4.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - tracepoints for basic cgroup management operations added

 - kernfs and cgroup path formatting functions updated to behave in the
   style of strlcpy()

 - non-critical bug fixes

* 'for-4.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  blkcg: Unlock blkcg_pol_mutex only once when cpd == NULL
  cgroup: fix error handling regressions in proc_cgroup_show() and cgroup_release_agent()
  cpuset: fix error handling regression in proc_cpuset_show()
  cgroup: add tracepoints for basic operations
  cgroup: make cgroup_path() and friends behave in the style of strlcpy()
  kernfs: remove kernfs_path_len()
  kernfs: make kernfs_path*() behave in the style of strlcpy()
  kernfs: add dummy implementation of kernfs_path_from_node()

2 files changed, 20 insertions, 70 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index dcd96aac02f5..cf4c636ff4da 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -110,8 +110,9 @@ static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a,
  * kn_to:   /n1/n2/n3         [depth=3]
  * result:  /../..
  *
- * return value: length of the string.  If greater than buflen,
- * then contents of buf are undefined.  On error, -1 is returned.
+ * Returns the length of the full path.  If the full length is equal to or
+ * greater than @buflen, @buf contains the truncated path with the trailing
+ * '\0'.  On error, -errno is returned.
  */
 static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
 					struct kernfs_node *kn_from,
@@ -119,9 +120,8 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
 {
 	struct kernfs_node *kn, *common;
 	const char parent_str[] = "/..";
-	size_t depth_from, depth_to, len = 0, nlen = 0;
-	char *p;
-	int i;
+	size_t depth_from, depth_to, len = 0;
+	int i, j;
 
 	if (!kn_from)
 		kn_from = kernfs_root(kn_to)->kn;
@@ -131,7 +131,7 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
 
 	common = kernfs_common_ancestor(kn_from, kn_to);
 	if (WARN_ON(!common))
-		return -1;
+		return -EINVAL;
 
 	depth_to = kernfs_depth(common, kn_to);
 	depth_from = kernfs_depth(common, kn_from);
@@ -144,22 +144,16 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
 			       len < buflen ? buflen - len : 0);
 
 	/* Calculate how many bytes we need for the rest */
-	for (kn = kn_to; kn != common; kn = kn->parent)
-		nlen += strlen(kn->name) + 1;
-
-	if (len + nlen >= buflen)
-		return len + nlen;
-
-	p = buf + len + nlen;
-	*p = '\0';
-	for (kn = kn_to; kn != common; kn = kn->parent) {
-		size_t tmp = strlen(kn->name);
-		p -= tmp;
-		memcpy(p, kn->name, tmp);
-		*(--p) = '/';
+	for (i = depth_to - 1; i >= 0; i--) {
+		for (kn = kn_to, j = 0; j < i; j++)
+			kn = kn->parent;
+		len += strlcpy(buf + len, "/",
+			       len < buflen ? buflen - len : 0);
+		len += strlcpy(buf + len, kn->name,
+			       len < buflen ? buflen - len : 0);
 	}
 
-	return len + nlen;
+	return len;
 }
 
 /**
@@ -186,29 +180,6 @@ 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_from_node - build path of node @to relative to @from.
  * @from: parent kernfs_node relative to which we need to build the path
  * @to: kernfs_node of interest
@@ -220,8 +191,9 @@ size_t kernfs_path_len(struct kernfs_node *kn)
  * path (which includes '..'s) as needed to reach from @from to @to is
  * returned.
  *
- * If @buf isn't long enough, the return value will be greater than @buflen
- * and @buf contents are undefined.
+ * Returns the length of the full path.  If the full length is equal to or
+ * greater than @buflen, @buf contains the truncated path with the trailing
+ * '\0'.  On error, -errno is returned.
  */
 int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from,
 			  char *buf, size_t buflen)
@@ -237,28 +209,6 @@ int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from,
 EXPORT_SYMBOL_GPL(kernfs_path_from_node);
 
 /**
- * kernfs_path - build full path of a given node
- * @kn: kernfs_node of interest
- * @buf: buffer to copy @kn's name into
- * @buflen: size of @buf
- *
- * Builds and returns the full path of @kn in @buf of @buflen bytes.  The
- * path is built from the end of @buf so the returned pointer usually
- * doesn't match @buf.  If @buf isn't long enough, @buf is nul terminated
- * and %NULL is returned.
- */
-char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
-{
-	int ret;
-
-	ret = kernfs_path_from_node(kn, NULL, buf, buflen);
-	if (ret < 0 || ret >= buflen)
-		return NULL;
-	return buf;
-}
-EXPORT_SYMBOL_GPL(kernfs_path);
-
-/**
  * pr_cont_kernfs_name - pr_cont name of a kernfs_node
  * @kn: kernfs_node of interest
  *
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 94374e435025..2b67bda2021b 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -21,14 +21,14 @@ DEFINE_SPINLOCK(sysfs_symlink_target_lock);
 
 void sysfs_warn_dup(struct kernfs_node *parent, const char *name)
 {
-	char *buf, *path = NULL;
+	char *buf;
 
 	buf = kzalloc(PATH_MAX, GFP_KERNEL);
 	if (buf)
-		path = kernfs_path(parent, buf, PATH_MAX);
+		kernfs_path(parent, buf, PATH_MAX);
 
 	WARN(1, KERN_WARNING "sysfs: cannot create duplicate filename '%s/%s'\n",
-	     path, name);
+	     buf, name);
 
 	kfree(buf);
 }