From 64df37a5c4d2e7911b14f1fa9a8498d5ce4d8582 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Mon, 30 Jan 2012 21:23:52 -0800
Subject: [PATCH] --- yaml --- r: 295473 b: refs/heads/master c:
 60f126d93b210ae708e2a5bb4a3be2121831f2a0 h: refs/heads/master i:   295471:
 8c8cca9b98ea975517087a853c1e850cb3345c2f v: v3

---
 [refs]                      |  2 +-
 trunk/fs/proc/proc_sysctl.c | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 475c26c4c166..a2a3648059c6 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 0eb97f38d2bfaea289b44c5140a7b04e7b369bad
+refs/heads/master: 60f126d93b210ae708e2a5bb4a3be2121831f2a0
diff --git a/trunk/fs/proc/proc_sysctl.c b/trunk/fs/proc/proc_sysctl.c
index 722ec116208d..e5601dc24088 100644
--- a/trunk/fs/proc/proc_sysctl.c
+++ b/trunk/fs/proc/proc_sysctl.c
@@ -73,6 +73,7 @@ static int namecmp(const char *name1, int len1, const char *name2, int len2)
 	return cmp;
 }
 
+/* Called under sysctl_lock */
 static struct ctl_table *find_entry(struct ctl_table_header **phead,
 	struct ctl_dir *dir, const char *name, int namelen)
 {
@@ -864,6 +865,18 @@ static struct ctl_dir *new_dir(struct ctl_table_set *set,
 	return new;
 }
 
+/**
+ * get_subdir - find or create a subdir with the specified name.
+ * @dir:  Directory to create the subdirectory in
+ * @name: The name of the subdirectory to find or create
+ * @namelen: The length of name
+ *
+ * Takes a directory with an elevated reference count so we know that
+ * if we drop the lock the directory will not go away.  Upon success
+ * the reference is moved from @dir to the returned subdirectory.
+ * Upon error an error code is returned and the reference on @dir is
+ * simply dropped.
+ */
 static struct ctl_dir *get_subdir(struct ctl_dir *dir,
 				  const char *name, int namelen)
 {
@@ -885,12 +898,14 @@ static struct ctl_dir *get_subdir(struct ctl_dir *dir,
 	if (!new)
 		goto failed;
 
+	/* Was the subdir added while we dropped the lock? */
 	subdir = find_subdir(dir, name, namelen);
 	if (!IS_ERR(subdir))
 		goto found;
 	if (PTR_ERR(subdir) != -ENOENT)
 		goto failed;
 
+	/* Nope.  Use the our freshly made directory entry. */
 	err = insert_header(dir, &new->header);
 	subdir = ERR_PTR(err);
 	if (err)
@@ -1190,6 +1205,7 @@ struct ctl_table_header *__register_sysctl_table(
 
 	spin_lock(&sysctl_lock);
 	dir = &set->dir;
+	/* Reference moved down the diretory tree get_subdir */
 	dir->header.nreg++;
 	spin_unlock(&sysctl_lock);