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authorAl Viro <viro@zeniv.linux.org.uk>2008-07-15 06:33:31 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2008-07-26 20:53:11 -0400
commitae7edecc9b8810770a8e5cb9a466ea4bdcfa8401 (patch)
tree8c0a244f4aea3eca5d8edf45665266b007eb046e
parentbd7b1533cd6a68c734062aa69394bec7e2b1718e (diff)
[PATCH] sysctl: keep track of tree relationships
In a sense, that's the heart of the series. It's based on the following property of the trees we are actually asked to add: they can be split into stem that is already covered by registered trees and crown that is entirely new. IOW, if a/b and a/c/d are introduced by our tree, then a/c is also introduced by it. That allows to associate tree and table entry with each node in the union; while directory nodes might be covered by many trees, only one will cover the node by its crown. And that will allow much saner logics for /proc/sys in the next patches. This patch introduces the data structures needed to keep track of that. When adding a sysctl table, we find a "parent" one. Which is to say, find the deepest node on its stem that already is present in one of the tables from our table set or its ancestor sets. That table will be our parent and that node in it - attachment point. Add our table to list anchored in parent, have it refer the parent and contents of attachment point. Also remember where its crown lives. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-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);