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SubjectRe: [PATCH 1/1] cgroups: introduce cft->read_seq()
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.

Paul


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