netdev - Re: /proc/net/dev is funky in 3.3.0

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Message-ID: <CAOMsUMLhfZ_nopcU1otBS+yiUzjNNYq5YewaYw_-JdhetBubpw@mail.gmail.com>
Date:	Tue, 3 Apr 2012 10:17:26 +0300
From:	Mihai Maruseac <mmaruseac@...acom.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Ben Greear <greearb@...delatech.com>,
	NetDev <netdev@...r.kernel.org>,
	Mihai Maruseac <mmaruseac@...acom.com>,
	Daniel Baluta <dbaluta@...acom.com>
Subject: Re: /proc/net/dev is funky in 3.3.0

On Tue, Apr 3, 2012 at 10:06 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Tue, 2012-04-03 at 08:36 +0200, Eric Dumazet wrote:
>
>> Hmm, I think I understand, commit f04565ddf52 added a regression here, I
>> will send a fix.
>>
>
> If you want to try following patch, please do so, I cant try it right
> now...
>
> I'll provide a proper changelog/attributions in a couple of hours, and
> make tests myself of course.
>
> Thanks
>
>  net/core/dev.c |   46 ++++++++++++----------------------------------
>  1 file changed, 12 insertions(+), 34 deletions(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 6c7dc9d..f7e7de3 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -4028,54 +4028,45 @@ static int dev_ifconf(struct net *net, char __user *arg)
>
>  #ifdef CONFIG_PROC_FS
>
> -#define BUCKET_SPACE (32 - NETDEV_HASHBITS)
> +#define BUCKET_SPACE (32 - NETDEV_HASHBITS - 1)
>
>  struct dev_iter_state {
>        struct seq_net_private p;
> -       unsigned int pos; /* bucket << BUCKET_SPACE + offset */
>  };
>
>  #define get_bucket(x) ((x) >> BUCKET_SPACE)
>  #define get_offset(x) ((x) & ((1 << BUCKET_SPACE) - 1))
>  #define set_bucket_offset(b, o) ((b) << BUCKET_SPACE | (o))
>
> -static inline struct net_device *dev_from_same_bucket(struct seq_file *seq)
> +static inline struct net_device *dev_from_same_bucket(struct seq_file *seq, loff_t *pos)
>  {
> -       struct dev_iter_state *state = seq->private;
>        struct net *net = seq_file_net(seq);
>        struct net_device *dev;
>        struct hlist_node *p;
>        struct hlist_head *h;
> -       unsigned int count, bucket, offset;
> +       unsigned int count = 0, offset = get_offset(*pos);
>
> -       bucket = get_bucket(state->pos);
> -       offset = get_offset(state->pos);
> -       h = &net->dev_name_head[bucket];
> -       count = 0;
> +       h = &net->dev_name_head[get_bucket(*pos)];
>        hlist_for_each_entry_rcu(dev, p, h, name_hlist) {
> -               if (count++ == offset) {
> -                       state->pos = set_bucket_offset(bucket, count);
> +               if (++count == offset)
>                        return dev;
> -               }
>        }
>
>        return NULL;
>  }
>
> -static inline struct net_device *dev_from_new_bucket(struct seq_file *seq)
> +static inline struct net_device *dev_from_bucket(struct seq_file *seq, loff_t *pos)
>  {
> -       struct dev_iter_state *state = seq->private;
>        struct net_device *dev;
>        unsigned int bucket;
>
> -       bucket = get_bucket(state->pos);
>        do {
> -               dev = dev_from_same_bucket(seq);
> +               dev = dev_from_same_bucket(seq, pos);
>                if (dev)
>                        return dev;
>
> -               bucket++;
> -               state->pos = set_bucket_offset(bucket, 0);
> +               bucket = get_bucket(*pos);
> +               *pos = set_bucket_offset(bucket + 1, 1);
>        } while (bucket < NETDEV_HASHENTRIES);
>
>        return NULL;
> @@ -4088,33 +4079,20 @@ static inline struct net_device *dev_from_new_bucket(struct seq_file *seq)
>  void *dev_seq_start(struct seq_file *seq, loff_t *pos)
>        __acquires(RCU)
>  {
> -       struct dev_iter_state *state = seq->private;
> -
>        rcu_read_lock();
>        if (!*pos)
>                return SEQ_START_TOKEN;
>
> -       /* check for end of the hash */
> -       if (state->pos == 0 && *pos > 1)
> +       if (get_bucket(*pos) >= NETDEV_HASHENTRIES)
>                return NULL;
>
> -       return dev_from_new_bucket(seq);
> +       return dev_from_bucket(seq, pos);
>  }
>
>  void *dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
>  {
> -       struct net_device *dev;
> -
>        ++*pos;
> -
> -       if (v == SEQ_START_TOKEN)
> -               return dev_from_new_bucket(seq);
> -
> -       dev = dev_from_same_bucket(seq);
> -       if (dev)
> -               return dev;
> -
> -       return dev_from_new_bucket(seq);
> +       return dev_from_bucket(seq, pos);
>  }
>
>  void dev_seq_stop(struct seq_file *seq, void *v)
>

Looks good to me.

Thanks Eric,
Mihai
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