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    SubjectRe: [PATCH 1/9 v3] cgroup: add cgroup_subsys->post_create()
    Hi Tejun,

    On 08.11.2012 20:07, Tejun Heo wrote:> Subject: cgroup: add
    cgroup_subsys->post_create()
    >
    > Currently, there's no way for a controller to find out whether a new
    > cgroup finished all ->create() allocatinos successfully and is
    > considered "live" by cgroup.

    I'd like add hierarchy support to net_prio and the first thing to
    do is to get rid of get_prioidx(). It looks like it would be nice to be
    able to use use_id and post_create() for this but as I read the code
    this might not work because the netdev might access resources allocated
    between create() and post_create(). So my question is would it make
    sense to move

    cgroup_create():

    if (ss->use_id) {
    err = alloc_css_id(ss, parent, cgrp);
    if (err)
    goto err_destroy;
    }

    part before create() or add some protection between create() and
    post_create() callback in net_prio. I have a patch but I see
    I could drop it completely if post_create() is there.

    cheers,
    daniel


    From 84fbbdf0dc5d3460389e39a00a3ee553ee55b563 Mon Sep 17 00:00:00 2001
    From: Daniel Wagner <daniel.wagner@bmw-carit.de>
    Date: Thu, 8 Nov 2012 17:17:21 +0100
    Subject: [PATCH] cgroups: net_prio: Use IDR library to assign netprio index

    get_prioidx() allocated a new id whenever it was called. put_prioidx()
    gave an id back. get_pioidx() could can reallocate the id later on.
    So that is exactly what IDR offers and so let's use it.

    Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
    ---
    net/core/netprio_cgroup.c | 51
    +++++++++--------------------------------------
    1 file changed, 9 insertions(+), 42 deletions(-)

    diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
    index 847c02b..3c1b612 100644
    --- a/net/core/netprio_cgroup.c
    +++ b/net/core/netprio_cgroup.c
    @@ -27,10 +27,7 @@

    #include <linux/fdtable.h>

    -#define PRIOIDX_SZ 128
    -
    -static unsigned long prioidx_map[PRIOIDX_SZ];
    -static DEFINE_SPINLOCK(prioidx_map_lock);
    +static DEFINE_IDA(netprio_ida);
    static atomic_t max_prioidx = ATOMIC_INIT(0);

    static inline struct cgroup_netprio_state *cgrp_netprio_state(struct
    cgroup *cgrp)
    @@ -39,34 +36,6 @@ static inline struct cgroup_netprio_state
    *cgrp_netprio_state(struct cgroup *cgr
    struct cgroup_netprio_state, css);
    }

    -static int get_prioidx(u32 *prio)
    -{
    - unsigned long flags;
    - u32 prioidx;
    -
    - spin_lock_irqsave(&prioidx_map_lock, flags);
    - prioidx = find_first_zero_bit(prioidx_map, sizeof(unsigned long) *
    PRIOIDX_SZ);
    - if (prioidx == sizeof(unsigned long) * PRIOIDX_SZ) {
    - spin_unlock_irqrestore(&prioidx_map_lock, flags);
    - return -ENOSPC;
    - }
    - set_bit(prioidx, prioidx_map);
    - if (atomic_read(&max_prioidx) < prioidx)
    - atomic_set(&max_prioidx, prioidx);
    - spin_unlock_irqrestore(&prioidx_map_lock, flags);
    - *prio = prioidx;
    - return 0;
    -}
    -
    -static void put_prioidx(u32 idx)
    -{
    - unsigned long flags;
    -
    - spin_lock_irqsave(&prioidx_map_lock, flags);
    - clear_bit(idx, prioidx_map);
    - spin_unlock_irqrestore(&prioidx_map_lock, flags);
    -}
    -
    static int extend_netdev_table(struct net_device *dev, u32 new_len)
    {
    size_t new_size = sizeof(struct netprio_map) +
    @@ -120,9 +89,9 @@ static struct cgroup_subsys_state *cgrp_create(struct
    cgroup *cgrp)
    if (cgrp->parent && cgrp_netprio_state(cgrp->parent)->prioidx)
    goto out;

    - ret = get_prioidx(&cs->prioidx);
    - if (ret < 0) {
    - pr_warn("No space in priority index array\n");
    + cs->prioidx = ida_simple_get(&netprio_ida, 0, 0, GFP_KERNEL);
    + if (cs->prioidx < 0) {
    + ret = cs->prioidx;
    goto out;
    }

    @@ -146,7 +115,7 @@ static void cgrp_destroy(struct cgroup *cgrp)
    map->priomap[cs->prioidx] = 0;
    }
    rtnl_unlock();
    - put_prioidx(cs->prioidx);
    + ida_simple_remove(&netprio_ida, cs->prioidx);
    kfree(cs);
    }

    @@ -284,12 +253,10 @@ struct cgroup_subsys net_prio_subsys = {
    .module = THIS_MODULE,

    /*
    - * net_prio has artificial limit on the number of cgroups and
    - * disallows nesting making it impossible to co-mount it with other
    - * hierarchical subsystems. Remove the artificially low PRIOIDX_SZ
    - * limit and properly nest configuration such that children follow
    - * their parents' configurations by default and are allowed to
    - * override and remove the following.
    + * net_prio has artificial limit on properly nest
    + * configuration such that children follow their parents'
    + * configurations by default and are allowed to override and
    + * remove the following.
    */
    .broken_hierarchy = true,
    };
    --
    1.7.11.7



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