lkml.org 
[lkml]   [2009]   [Jun]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Subject[PATCH v2 10/10] nf_conntrack: Use rcu_barrier() and fix kmem_cache_create flags
    From
    Date

    Adjusting SLAB_DESTROY_BY_RCU flags.

    kmem_cache_create("nf_conntrack", ...) does not need the
    SLAB_DESTROY_BY_RCU flag. But the
    kmem_cache_create("nf_conntrack_expect", ...) should use the
    SLAB_DESTROY_BY_RCU flag, because it uses a call_rcu() callback to
    invoke kmem_cache_free().

    RCU barriers, rcu_barrier(), is inserted two places.

    In nf_conntrack_expect.c nf_conntrack_expect_fini() before the
    kmem_cache_destroy(), even though the use of the SLAB_DESTROY_BY_RCU
    flag, because slub does not (currently) handle rcu sync correctly.

    And in nf_conntrack_extend.c nf_ct_extend_unregister(), inorder to
    wait for completion of callbacks to __nf_ct_ext_free_rcu(), which is
    invoked by __nf_ct_ext_add(). It might be more efficient to call
    rcu_barrier() in nf_conntrack_core.c nf_conntrack_cleanup_net(), but
    thats make it more difficult to read the code (as the callback code
    in located in nf_conntrack_extend.c).

    Signed-off-by: Jesper Dangaard Brouer <hawk@comx.dk>
    ---

    net/netfilter/nf_conntrack_core.c | 2 +-
    net/netfilter/nf_conntrack_expect.c | 11 +++++++++--
    net/netfilter/nf_conntrack_extend.c | 2 +-
    3 files changed, 11 insertions(+), 4 deletions(-)


    diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
    index 5f72b94..438ce84 100644
    --- a/net/netfilter/nf_conntrack_core.c
    +++ b/net/netfilter/nf_conntrack_core.c
    @@ -1242,7 +1242,7 @@ static int nf_conntrack_init_init_net(void)

    nf_conntrack_cachep = kmem_cache_create("nf_conntrack",
    sizeof(struct nf_conn),
    - 0, SLAB_DESTROY_BY_RCU, NULL);
    + 0, 0, NULL);
    if (!nf_conntrack_cachep) {
    printk(KERN_ERR "Unable to create nf_conn slab cache\n");
    ret = -ENOMEM;
    diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
    index afde8f9..56227c2 100644
    --- a/net/netfilter/nf_conntrack_expect.c
    +++ b/net/netfilter/nf_conntrack_expect.c
    @@ -593,7 +593,7 @@ int nf_conntrack_expect_init(struct net *net)
    if (net_eq(net, &init_net)) {
    nf_ct_expect_cachep = kmem_cache_create("nf_conntrack_expect",
    sizeof(struct nf_conntrack_expect),
    - 0, 0, NULL);
    + 0, SLAB_DESTROY_BY_RCU, NULL);
    if (!nf_ct_expect_cachep)
    goto err2;
    }
    @@ -617,8 +617,15 @@ err1:
    void nf_conntrack_expect_fini(struct net *net)
    {
    exp_proc_remove(net);
    - if (net_eq(net, &init_net))
    + if (net_eq(net, &init_net)) {
    + /* hawk@comx.dk 2009-06-24: The rcu_barrier() can be
    + * removed once the sl*b allocators has been fixed
    + * regarding handling the SLAB_DESTROY_BY_RCU flag
    + * correctly.
    + */
    + rcu_barrier(); /* Wait for call_rcu() before destroy */
    kmem_cache_destroy(nf_ct_expect_cachep);
    + }
    nf_ct_free_hashtable(net->ct.expect_hash, net->ct.expect_vmalloc,
    nf_ct_expect_hsize);
    }
    diff --git a/net/netfilter/nf_conntrack_extend.c b/net/netfilter/nf_conntrack_extend.c
    index 4b2c769..fef95be 100644
    --- a/net/netfilter/nf_conntrack_extend.c
    +++ b/net/netfilter/nf_conntrack_extend.c
    @@ -186,6 +186,6 @@ void nf_ct_extend_unregister(struct nf_ct_ext_type *type)
    rcu_assign_pointer(nf_ct_ext_types[type->id], NULL);
    update_alloc_size(type);
    mutex_unlock(&nf_ct_ext_type_mutex);
    - synchronize_rcu();
    + rcu_barrier(); /* Wait for completion of call_rcu()'s */
    }
    EXPORT_SYMBOL_GPL(nf_ct_extend_unregister);


    \
     
     \ /
      Last update: 2009-06-24 11:43    [W:0.031 / U:1.128 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site