[RFC PATCH 1/3] procfs: check uniq proc_dir_entry subdir name

[Chen Hanxiao <chenhanxiao@xxxxxxxxxxxxxx>]

Check whether a proc dir has a subdir
with a specific name.
Will be used in a later patch.

Signed-off-by: Chen Hanxiao <chenhanxiao@xxxxxxxxxxxxxx>
---
 fs/proc/generic.c       | 15 +++++++++++++++
 include/linux/proc_fs.h |  3 +++
 2 files changed, 18 insertions(+)

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index b7f268e..4d576c2 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -173,6 +173,21 @@ static const struct inode_operations proc_link_inode_operations = {
 	.follow_link	= proc_follow_link,
 };
 
+/* check whether dir has @name member */
+struct proc_dir_entry *proc_uniq_dir(struct proc_dir_entry *de, char *name)
+{
+	spin_lock(&proc_subdir_lock);
+	for (de = de->subdir; de ; de = de->next) {
+		if (!strcmp(de->name, name)) {
+			spin_unlock(&proc_subdir_lock);
+			return de;
+		}
+	}
+	spin_unlock(&proc_subdir_lock);
+	return NULL;
+}
+EXPORT_SYMBOL(proc_uniq_dir);
+
 /*
  * Don't create negative dentries here, return -ENOENT by hand
  * instead.
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 9d117f6..38e87aa 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -41,6 +41,7 @@ extern void *proc_get_parent_data(const struct inode *);
 extern void proc_remove(struct proc_dir_entry *);
 extern void remove_proc_entry(const char *, struct proc_dir_entry *);
 extern int remove_proc_subtree(const char *, struct proc_dir_entry *);
+extern struct proc_dir_entry *proc_uniq_dir(struct proc_dir_entry *, char *);
 
 #else /* CONFIG_PROC_FS */
 
@@ -71,6 +72,8 @@ static inline void *proc_get_parent_data(const struct inode *inode) { BUG(); ret
 static inline void proc_remove(struct proc_dir_entry *de) {}
 #define remove_proc_entry(name, parent) do {} while (0)
 static inline int remove_proc_subtree(const char *name, struct proc_dir_entry *parent) { return 0; }
+static inline struct proc_dir_entry *proc_uniq_dir(struct proc_dir_entry *,
+	char *) {return 0; }
 
 #endif /* CONFIG_PROC_FS */
 
-- 
1.9.0

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