[PATCH 56/59] sysctl: factor out sysctl_head_next from do_sysctl

Eric W. Biederman
2007-01-16T16:44:31Z

The current logic to walk through the list of sysctl table
headers is slightly painful and implement in a way it cannot
be used by code outside sysctl.c

I am in the process of implementing a version of the sysctl
proc support that instead of using the proc generic non-caching
monster, just uses the existing sysctl data structure as
backing store for building the dcache entries and for doing
directory reads. To use the existing data structures however
I need a way to get at them.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
include/linux/sysctl.h | 4 +++
kernel/sysctl.c | 57 +++++++++++++++++++++++++++++++++++------------
2 files changed, 46 insertions(+), 15 deletions(-)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 6113f3b..81ee9ea 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -923,6 +923,10 @@ enum
#ifdef __KERNEL__
#include <linux/list.h>

+/* For the /proc/sys support */
+extern struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev);
+extern void sysctl_head_finish(struct ctl_table_header *prev);
+
extern void sysctl_init(void);

typedef struct ctl_table ctl_table;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 5beee1f..ca2831a 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1066,6 +1066,42 @@ static void start_unregistering(struct ctl_table_header *p)
list_del_init(&p->ctl_entry);
}

+void sysctl_head_finish(struct ctl_table_header *head)
+{
+ if (!head)
+ return;
+ spin_lock(&sysctl_lock);
+ unuse_table(head);
+ spin_unlock(&sysctl_lock);
+}
+
+struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev)
+{
+ struct ctl_table_header *head;
+ struct list_head *tmp;
+ spin_lock(&sysctl_lock);
+ if (prev) {
+ tmp = &prev->ctl_entry;
+ unuse_table(prev);
+ goto next;
+ }
+ tmp = &root_table_header.ctl_entry;
+ for (;;) {
+ head = list_entry(tmp, struct ctl_table_header, ctl_entry);
+
+ if (!use_table(head))
+ goto next;
+ spin_unlock(&sysctl_lock);
+ return head;
+ next:
+ tmp = tmp->next;
+ if (tmp == &root_table_header.ctl_entry)
+ break;
+ }
+ spin_unlock(&sysctl_lock);
+ return NULL;
+}
+
void __init sysctl_init(void)
{
#ifdef CONFIG_PROC_SYSCTL
@@ -1077,6 +1113,7 @@ void __init sysctl_init(void)
int do_sysctl(int __user *name, int nlen, void __user *oldval, size_t __user *oldlenp,
void __user *newval, size_t newlen)
{
+ struct ctl_table_header *head;
struct list_head *tmp;
int error = -ENOTDIR;

@@ -1087,26 +1124,16 @@ int do_sysctl(int __user *name, int nlen, void __user *oldval, size_t __user *ol
if (!oldlenp || get_user(old_len, oldlenp))
return -EFAULT;
}
- spin_lock(&sysctl_lock);
- tmp = &root_table_header.ctl_entry;
- do {
- struct ctl_table_header *head =
- list_entry(tmp, struct ctl_table_header, ctl_entry);

- if (!use_table(head))
- continue;
-
- spin_unlock(&sysctl_lock);
+ for (head = sysctl_head_next(NULL); head; head = sysctl_head_next(head)) {

error = parse_table(name, nlen, oldval, oldlenp,
newval, newlen, head->ctl_table);
-
- spin_lock(&sysctl_lock);
- unuse_table(head);
- if (error != -ENOTDIR)
+ if (error != -ENOTDIR) {
+ sysctl_head_finish(head);
break;
- } while ((tmp = tmp->next) != &root_table_header.ctl_entry);
- spin_unlock(&sysctl_lock);
+ }
+ }
return error;
}

--
1.4.4.1.g278f