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Subject[v2 069/115] sysctl: split ->count into ctl_procfs_refs and ctl_header_refs
Date
This is not necessary at this point, but will be later when we replace
the sysctl implementation with one that uses ctl_table_header objects
as directories.

Signed-off-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
---
include/linux/sysctl.h | 8 +++++++-
kernel/sysctl.c | 21 ++++++++++++---------
2 files changed, 19 insertions(+), 10 deletions(-)
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 4ed5235..0f41beb 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -1046,7 +1046,13 @@ struct ctl_table_header
/* references to this header from contexts that
* can access fields of this header */
int ctl_use_refs;
- int count;
+ /* references to this header from procfs inodes.
+ * procfs embeds a pointer to the header in proc_inode */
+ int ctl_procfs_refs;
+ /* counts references to this header from other
+ * headers (through ->parent) plus the reference
+ * returned by __register_sysctl_paths */
+ int ctl_header_refs;
};
struct rcu_head rcu;
};
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index e4ec23e..48a1ffd 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -200,7 +200,7 @@ static int sysrq_sysctl_handler(ctl_table *table, int write,
static struct ctl_table root_table[];
static struct ctl_table_root sysctl_table_root;
static struct ctl_table_header root_table_header = {
- {{.count = 1,
+ {{.ctl_header_refs = 1,
.ctl_table = root_table,
.ctl_entry = LIST_HEAD_INIT(sysctl_table_root.default_set.list),}},
.root = &sysctl_table_root,
@@ -1554,7 +1554,7 @@ static void start_unregistering(struct ctl_table_header *p)
void sysctl_head_get(struct ctl_table_header *head)
{
spin_lock(&sysctl_lock);
- head->count++;
+ head->ctl_procfs_refs++;
spin_unlock(&sysctl_lock);
}

@@ -1566,7 +1566,8 @@ static void free_head(struct rcu_head *rcu)
void sysctl_head_put(struct ctl_table_header *head)
{
spin_lock(&sysctl_lock);
- if (!--head->count)
+ head->ctl_procfs_refs--;
+ if ((head->ctl_procfs_refs == 0) && (head->ctl_header_refs == 0))
call_rcu(&head->rcu, free_head);
spin_unlock(&sysctl_lock);
}
@@ -1877,7 +1878,7 @@ struct ctl_table_header *__register_sysctl_paths(
INIT_LIST_HEAD(&header->ctl_entry);
header->unregistering = NULL;
header->root = root;
- header->count = 1;
+ header->ctl_header_refs = 1;
#ifdef CONFIG_SYSCTL_SYSCALL_CHECK
if (sysctl_check_table(namespaces, header->ctl_table)) {
kfree(header);
@@ -1897,7 +1898,7 @@ struct ctl_table_header *__register_sysctl_paths(
try_attach(p, header);
}
}
- header->parent->count++;
+ header->parent->ctl_header_refs++;
list_add_tail(&header->ctl_entry, &header->set->list);
spin_unlock(&sysctl_lock);

@@ -1937,12 +1938,14 @@ void unregister_sysctl_table(struct ctl_table_header * header)

spin_lock(&sysctl_lock);
start_unregistering(header);
- if (!--header->parent->count) {
+ if (!--header->parent->ctl_header_refs) {
WARN_ON(1);
- call_rcu(&header->parent->rcu, free_head);
+ if (!header->parent->ctl_procfs_refs)
+ call_rcu(&header->parent->rcu, free_head);
}
- if (!--header->count)
- call_rcu(&header->rcu, free_head);
+ if (!--header->ctl_header_refs)
+ if (!header->ctl_procfs_refs)
+ call_rcu(&header->rcu, free_head);
spin_unlock(&sysctl_lock);
}

--
1.7.5.134.g1c08b


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