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SubjectRe: [PATCH 1/1] cgroups: introduce cft->read_seq()
Quoting Paul Menage (menage@google.com):
> On Wed, Apr 2, 2008 at 6:01 PM, Serge E. Hallyn <serue@us.ibm.com> wrote:
> > + /*
> > + * read_seq() is used for outputting a simple sequence
> > + * using seqfile.
> > + */
> > + int (*read_seq) (struct cgroup *cont, struct cftype *cft,
> > + struct seq_file *m);
>
> Maybe make it read_seq_string() to emphasise that it's not intended
> for structured data?
>
> >
> > -static int cgroup_seqfile_show(struct seq_file *m, void *arg)
> > +static int cgroup_map_seqfile_show(struct seq_file *m, void *arg)
> > {
> > struct cgroup_seqfile_state *state = m->private;
> > struct cftype *cft = state->cft;
> > @@ -1529,6 +1529,13 @@ static int cgroup_seqfile_show(struct seq_file *m, void *arg)
> > return cft->read_map(state->cgroup, cft, &cb);
> > }
>
> I think you can make this simpler - have cgroup_seqfile_show() switch
> based on whether the cft has a read_seq_string or a read_map, and then
> you only need one function.
>
> >
> > +static int cgroup_simple_seqfile_show(struct seq_file *m, void *arg)
> > +{
> > + struct cgroup_seqfile_state *state = m->private;
> > + struct cftype *cft = state->cft;
> > + return cft->read_seq(state->cgroup, cft, m);
> > +}
> > +
> > int cgroup_seqfile_release(struct inode *inode, struct file *file)
> > {
> > struct seq_file *seq = file->private_data;
> > @@ -1562,7 +1569,18 @@ static int cgroup_file_open(struct inode *inode, struct file *file)
> > state->cft = cft;
> > state->cgroup = __d_cgrp(file->f_dentry->d_parent);
> > file->f_op = &cgroup_seqfile_operations;
> > - err = single_open(file, cgroup_seqfile_show, state);
> > + err = single_open(file, cgroup_map_seqfile_show, state);
> > + if (err < 0)
> > + kfree(state);
> > + } else if (cft->read_seq) {
> > + struct cgroup_seqfile_state *state =
> > + kzalloc(sizeof(*state), GFP_USER);
> > + if (!state)
> > + return -ENOMEM;
> > + state->cft = cft;
> > + state->cgroup = __d_cgrp(file->f_dentry->d_parent);
> > + file->f_op = &cgroup_seqfile_operations;
> > + err = single_open(file, cgroup_simple_seqfile_show, state);
> > if (err < 0)
> > kfree(state);
>
> and this arm can just be eliminated, by adding "||
> cft->read_seq_string" to the test for cft_read_seq_map above.
>
> It was always my intention that cgroup_seqfile_show() be able to
> handle multiple data types, but up until now we only had one.

Thanks Paul, will do each of these.

-serge


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