diff options
| -rw-r--r-- | include/linux/cgroup.h | 19 | ||||
| -rw-r--r-- | kernel/cgroup.c | 53 |
2 files changed, 71 insertions, 1 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 058371c5d360..0a3ab670dd2f 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -166,6 +166,16 @@ struct css_set { }; +/* + * cgroup_map_cb is an abstract callback API for reporting map-valued + * control files + */ + +struct cgroup_map_cb { + int (*fill)(struct cgroup_map_cb *cb, const char *key, u64 value); + void *state; +}; + /* struct cftype: * * The files in the cgroup filesystem mostly have a very simple read/write @@ -194,6 +204,15 @@ struct cftype { * single integer. Use it in place of read() */ u64 (*read_u64) (struct cgroup *cgrp, struct cftype *cft); + /* + * read_map() is used for defining a map of key/value + * pairs. It should call cb->fill(cb, key, value) for each + * entry. The key/value pairs (and their ordering) should not + * change between reboots. + */ + int (*read_map) (struct cgroup *cont, struct cftype *cft, + struct cgroup_map_cb *cb); + ssize_t (*write) (struct cgroup *cgrp, struct cftype *cft, struct file *file, const char __user *buf, size_t nbytes, loff_t *ppos); diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 57afdde871ac..693bcc03188b 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1492,6 +1492,46 @@ static ssize_t cgroup_file_read(struct file *file, char __user *buf, return -EINVAL; } +/* + * seqfile ops/methods for returning structured data. Currently just + * supports string->u64 maps, but can be extended in future. + */ + +struct cgroup_seqfile_state { + struct cftype *cft; + struct cgroup *cgroup; +}; + +static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value) +{ + struct seq_file *sf = cb->state; + return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value); +} + +static int cgroup_seqfile_show(struct seq_file *m, void *arg) +{ + struct cgroup_seqfile_state *state = m->private; + struct cftype *cft = state->cft; + struct cgroup_map_cb cb = { + .fill = cgroup_map_add, + .state = m, + }; + return cft->read_map(state->cgroup, cft, &cb); +} + +int cgroup_seqfile_release(struct inode *inode, struct file *file) +{ + struct seq_file *seq = file->private_data; + kfree(seq->private); + return single_release(inode, file); +} + +static struct file_operations cgroup_seqfile_operations = { + .read = seq_read, + .llseek = seq_lseek, + .release = cgroup_seqfile_release, +}; + static int cgroup_file_open(struct inode *inode, struct file *file) { int err; @@ -1504,7 +1544,18 @@ static int cgroup_file_open(struct inode *inode, struct file *file) cft = __d_cft(file->f_dentry); if (!cft) return -ENODEV; - if (cft->open) + if (cft->read_map) { + 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_seqfile_show, state); + if (err < 0) + kfree(state); + } else if (cft->open) err = cft->open(inode, file); else err = 0; |