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()

1 files changed, 17 insertions, 67 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
  *