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-rw-r--r--include/linux/sysctl.h3
-rw-r--r--kernel/sysctl.c63
2 files changed, 66 insertions, 0 deletions
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 956264d09ba..3f6599aeb0d 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -1083,6 +1083,9 @@ struct ctl_table_header
struct ctl_table *ctl_table_arg;
struct ctl_table_root *root;
struct ctl_table_set *set;
+ struct ctl_table *attached_by;
+ struct ctl_table *attached_to;
+ struct ctl_table_header *parent;
};
/* struct ctl_path describes where in the hierarchy a table is added */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 60d9357e717..c9a0af88703 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1680,6 +1680,52 @@ static __init int sysctl_init(void)
core_initcall(sysctl_init);
+static int is_branch_in(struct ctl_table *branch, struct ctl_table *table)
+{
+ struct ctl_table *p;
+ const char *s = branch->procname;
+
+ /* branch should have named subdirectory as its first element */
+ if (!s || !branch->child)
+ return 0;
+
+ /* ... and nothing else */
+ if (branch[1].procname || branch[1].ctl_name)
+ return 0;
+
+ /* table should contain subdirectory with the same name */
+ for (p = table; p->procname || p->ctl_name; p++) {
+ if (!p->child)
+ continue;
+ if (p->procname && strcmp(p->procname, s) == 0)
+ return 1;
+ }
+ return 0;
+}
+
+/* see if attaching q to p would be an improvement */
+static void try_attach(struct ctl_table_header *p, struct ctl_table_header *q)
+{
+ struct ctl_table *to = p->ctl_table, *by = q->ctl_table;
+ int is_better = 0;
+ int not_in_parent = !p->attached_by;
+
+ while (is_branch_in(by, to)) {
+ if (by == q->attached_by)
+ is_better = 1;
+ if (to == p->attached_by)
+ not_in_parent = 1;
+ by = by->child;
+ to = to->child;
+ }
+
+ if (is_better && not_in_parent) {
+ q->attached_by = by;
+ q->attached_to = to;
+ q->parent = p;
+ }
+}
+
/**
* __register_sysctl_paths - register a sysctl hierarchy
* @root: List of sysctl headers to register on
@@ -1759,6 +1805,7 @@ struct ctl_table_header *__register_sysctl_paths(
struct ctl_table_header *header;
struct ctl_table *new, **prevp;
unsigned int n, npath;
+ struct ctl_table_set *set;
/* Count the path components */
for (npath = 0; path[npath].ctl_name || path[npath].procname; ++npath)
@@ -1809,6 +1856,18 @@ struct ctl_table_header *__register_sysctl_paths(
#endif
spin_lock(&sysctl_lock);
header->set = lookup_header_set(root, namespaces);
+ header->attached_by = header->ctl_table;
+ header->attached_to = root_table;
+ header->parent = &root_table_header;
+ for (set = header->set; set; set = set->parent) {
+ struct ctl_table_header *p;
+ list_for_each_entry(p, &set->list, ctl_entry) {
+ if (p->unregistering)
+ continue;
+ try_attach(p, header);
+ }
+ }
+ header->parent->count++;
list_add_tail(&header->ctl_entry, &header->set->list);
spin_unlock(&sysctl_lock);
@@ -1864,6 +1923,10 @@ void unregister_sysctl_table(struct ctl_table_header * header)
spin_lock(&sysctl_lock);
start_unregistering(header);
+ if (!--header->parent->count) {
+ WARN_ON(1);
+ kfree(header->parent);
+ }
if (!--header->count)
kfree(header);
spin_unlock(&sysctl_lock);