Re: [PATCH] net: Revert "fib_trie: use seq_file_net rather than seq->private"

[David Ahern]

On 6/4/14, 4:11 PM, David Ahern wrote:
> On 6/4/14, 4:02 PM, Sasha Levin wrote:
> > This reverts commit 30f38d2fdd79f13fc929489f7e6e517b4a4bfe63.
> >
> > fib_triestat is surrounded by a big lie: while it claims that it's a
> > seq_file (fib_triestat_seq_open, fib_triestat_seq_show), it isn't:
> >
> >     static const struct file_operations fib_triestat_fops = {
> >             .owner  = THIS_MODULE,
> >             .open   = fib_triestat_seq_open,
> >             .read   = seq_read,
> >             .llseek = seq_lseek,
> >             .release = single_release_net,
> >     };
> >
> > Yes, fib_triestat is just a regular file.

If you compare fib_trie to fib_triestat the only difference is the use 
of single_open_net and single_release_net by fib_triestat.

single_open_net is a wrapper to single_open passing struct net as the 
private data. single_open is for seq_files:


int single_open(struct file *file, int (*show)(struct seq_file *, void *),
        void *data)
{
    struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
    int res = -ENOMEM;

    if (op) {
        op->start = single_start;
        op->next = single_next;
        op->stop = single_stop;
        op->show = show;
        res = seq_open(file, op);
        if (!res)
            ((struct seq_file *)file->private_data)->private = data;

Where is the problem using seq_file_net in fib_triestat_seq_show:

static int fib_triestat_seq_show(struct seq_file *seq, void *v)
{
    struct net *net = (struct net *)seq->private;

where

static inline struct net *seq_file_net(struct seq_file *seq)
{
#ifdef CONFIG_NET_NS
    return ((struct seq_net_private *)seq->private)->net;
#else
    return &init_net;
#endif
}

David
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