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    Subject[v2 078/115] sysctl: alloc ctl_table_header with kmem_cache
    Date
    Because now ctl_table_header objects are allocated with a fixed size
    buffer (sizeof(struct ctl_table_header)) we can do the allocations
    with kmem_cache.

    Also, by making sure that the objects that are returned to the cache
    are in a sane state we don't waste time reinitializing every field
    after kmem_cache_alloc. We only initialize fields that were not left
    with a sane value before returning an object to the cache.

    Signed-off-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
    ---
    kernel/sysctl.c | 48 +++++++++++++++++++++++++++++++++++++++---------
    1 files changed, 39 insertions(+), 9 deletions(-)

    diff --git a/kernel/sysctl.c b/kernel/sysctl.c
    index d777e89..c207c19 100644
    --- a/kernel/sysctl.c
    +++ b/kernel/sysctl.c
    @@ -198,6 +198,9 @@ static int sysrq_sysctl_handler(ctl_table *table, int write,

    #endif

    +/* cache for ctl_table_header objects */
    +static struct kmem_cache *sysctl_header_cachep;
    +
    /* uses default ops */
    static const struct ctl_table_group_ops root_table_group_ops = { };

    @@ -1553,7 +1556,9 @@ void sysctl_proc_inode_get(struct ctl_table_header *head)

    static void free_head(struct rcu_head *rcu)
    {
    - kfree(container_of(rcu, struct ctl_table_header, rcu));
    + struct ctl_table_header *header;
    + header = container_of(rcu, struct ctl_table_header, rcu);
    + kmem_cache_free(sysctl_header_cachep, header);
    }

    void sysctl_proc_inode_put(struct ctl_table_header *head)
    @@ -1664,6 +1669,8 @@ int sysctl_perm(struct ctl_table_group *group, struct ctl_table *table, int op)
    return test_perm(mode, op);
    }

    +static void sysctl_header_ctor(void *data);
    +
    __init int sysctl_init(void)
    {
    struct ctl_table_header *kern_header, *vm_header, *fs_header,
    @@ -1672,6 +1679,12 @@ __init int sysctl_init(void)
    struct ctl_table_header *binfmt_misc_header;
    #endif

    + sysctl_header_cachep = kmem_cache_create("sysctl_header_cachep",
    + sizeof(struct ctl_table_header),
    + 0, 0, &sysctl_header_ctor);
    + if (!sysctl_header_cachep)
    + goto fail_alloc_cachep;
    +
    kern_header = register_sysctl_paths(kern_path, kern_table);
    if (kern_header == NULL)
    goto fail_register_kern;
    @@ -1715,6 +1728,8 @@ fail_register_fs:
    fail_register_vm:
    unregister_sysctl_table(kern_header);
    fail_register_kern:
    + kmem_cache_destroy(sysctl_header_cachep);
    +fail_alloc_cachep:
    return -ENOMEM;
    }

    @@ -1735,19 +1750,34 @@ static int ctl_path_items(const struct ctl_path *path)
    return n;
    }

    +static void sysctl_header_ctor(void *data)
    +{
    + struct ctl_table_header *h = data;
    +
    + h->ctl_use_refs = 0;
    + h->ctl_procfs_refs = 0;
    + h->ctl_header_refs = 0;
    +
    + INIT_LIST_HEAD(&h->ctl_entry);
    + INIT_LIST_HEAD(&h->ctl_subdirs);
    + INIT_LIST_HEAD(&h->ctl_tables);
    +}

    static struct ctl_table_header *alloc_sysctl_header(struct ctl_table_group *group)
    {
    struct ctl_table_header *h;

    - h = kzalloc(sizeof(*h), GFP_KERNEL);
    + h = kmem_cache_alloc(sysctl_header_cachep, GFP_KERNEL);
    if (!h)
    return NULL;

    + /* - all _refs members are zero before freeing
    + * - all list_head members point to themselves (empty lists) */
    +
    + h->ctl_table_arg = NULL;
    + h->unregistering = NULL;
    h->ctl_group = group;
    - INIT_LIST_HEAD(&h->ctl_entry);
    - INIT_LIST_HEAD(&h->ctl_subdirs);
    - INIT_LIST_HEAD(&h->ctl_tables);
    +
    return h;
    }

    @@ -1905,12 +1935,12 @@ static struct ctl_table_header *sysctl_mkdirs(struct ctl_table_header *parent,
    parent = mkdir_netns_corresp(parent, group, &__netns_corresp);

    if (__netns_corresp)
    - kfree(__netns_corresp);
    + kmem_cache_free(sysctl_header_cachep, __netns_corresp);

    /* free unused pre-allocated entries */
    for (i = 0; i < nr_dirs; i++)
    if (dirs[i])
    - kfree(dirs[i]);
    + kmem_cache_free(sysctl_header_cachep, dirs[i]);

    return parent;

    @@ -1918,7 +1948,7 @@ err_alloc_coresp:
    i = nr_dirs;
    err_alloc_dir:
    for (i--; i >= 0; i--)
    - kfree(dirs[i]);
    + kmem_cache_free(sysctl_header_cachep, dirs[i]);
    return NULL;

    }
    @@ -1991,7 +2021,7 @@ struct ctl_table_header *__register_sysctl_paths(struct ctl_table_group *group,

    header->parent = sysctl_mkdirs(&root_table_header, group, path, nr_dirs);
    if (!header->parent) {
    - kfree(header);
    + kmem_cache_free(sysctl_header_cachep, header);
    return NULL;
    }

    --
    1.7.5.134.g1c08b


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