[PATCH] sysctl: factor out sysctl_head_next from do_sysctl

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.

[akpm@osdl.org: warning fix]
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 396b8d984c5d310febe993cd27e61d7bce613c87..72ba58b362d8e1afc7ae9288f2035f45a19e18a4 100644 (file)
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -924,6 +924,10 @@ 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 6ccb6cc19e28bb9c91efbb9b5830fefc3000ab62..c3e2ac9cb5fb19e9158dc833ce6309d129c89d2d 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1070,6 +1070,42 @@ 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
@@ -1081,7 +1117,7 @@ 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 list_head *tmp;
+       struct ctl_table_header *head;
        int error = -ENOTDIR;
 
        if (nlen <= 0 || nlen >= CTL_MAXNAME)
@@ -1091,26 +1127,16 @@ 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;
 }