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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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