cpuset: convert away from cftype->read()
In preparation of conversion to kernfs, cgroup file handling is being consolidated so that it can be easily mapped to the seq_file based interface of kernfs. All users of cftype->read() can be easily served, usually better, by seq_file and other methods. Rename cpuset_common_file_read() to cpuset_common_read_seq_string() and convert it to use read_seq_string() interface instead. This not only simplifies the code but also makes it more versatile. Before, the file couldn't output if the result is longer than PAGE_SIZE. After the conversion, seq_file automatically grows the buffer until the output can fit. This patch doesn't make any visible behavior changes except for being able to handle output larger than PAGE_SIZE. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
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@ -1731,66 +1731,43 @@ out_unlock:
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* used, list of ranges of sequential numbers, is variable length,
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* and since these maps can change value dynamically, one could read
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* gibberish by doing partial reads while a list was changing.
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* A single large read to a buffer that crosses a page boundary is
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* ok, because the result being copied to user land is not recomputed
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* across a page fault.
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*/
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static size_t cpuset_sprintf_cpulist(char *page, struct cpuset *cs)
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{
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size_t count;
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mutex_lock(&callback_mutex);
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count = cpulist_scnprintf(page, PAGE_SIZE, cs->cpus_allowed);
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mutex_unlock(&callback_mutex);
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return count;
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}
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static size_t cpuset_sprintf_memlist(char *page, struct cpuset *cs)
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{
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size_t count;
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mutex_lock(&callback_mutex);
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count = nodelist_scnprintf(page, PAGE_SIZE, cs->mems_allowed);
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mutex_unlock(&callback_mutex);
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return count;
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}
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static ssize_t cpuset_common_file_read(struct cgroup_subsys_state *css,
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struct cftype *cft, struct file *file,
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char __user *buf, size_t nbytes,
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loff_t *ppos)
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static int cpuset_common_read_seq_string(struct cgroup_subsys_state *css,
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struct cftype *cft,
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struct seq_file *sf)
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{
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struct cpuset *cs = css_cs(css);
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cpuset_filetype_t type = cft->private;
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char *page;
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ssize_t retval = 0;
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char *s;
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ssize_t count;
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char *buf, *s;
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int ret = 0;
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if (!(page = (char *)__get_free_page(GFP_TEMPORARY)))
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return -ENOMEM;
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count = seq_get_buf(sf, &buf);
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s = buf;
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s = page;
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mutex_lock(&callback_mutex);
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switch (type) {
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case FILE_CPULIST:
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s += cpuset_sprintf_cpulist(s, cs);
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s += cpulist_scnprintf(s, count, cs->cpus_allowed);
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break;
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case FILE_MEMLIST:
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s += cpuset_sprintf_memlist(s, cs);
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s += nodelist_scnprintf(s, count, cs->mems_allowed);
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break;
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default:
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retval = -EINVAL;
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goto out;
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ret = -EINVAL;
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goto out_unlock;
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}
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*s++ = '\n';
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retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page);
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out:
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free_page((unsigned long)page);
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return retval;
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if (s < buf + count - 1) {
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*s++ = '\n';
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seq_commit(sf, s - buf);
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} else {
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seq_commit(sf, -1);
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}
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out_unlock:
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mutex_unlock(&callback_mutex);
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return ret;
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}
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static u64 cpuset_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
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@ -1847,7 +1824,7 @@ static s64 cpuset_read_s64(struct cgroup_subsys_state *css, struct cftype *cft)
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static struct cftype files[] = {
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{
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.name = "cpus",
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.read = cpuset_common_file_read,
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.read_seq_string = cpuset_common_read_seq_string,
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.write_string = cpuset_write_resmask,
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.max_write_len = (100U + 6 * NR_CPUS),
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.private = FILE_CPULIST,
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@ -1855,7 +1832,7 @@ static struct cftype files[] = {
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{
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.name = "mems",
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.read = cpuset_common_file_read,
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.read_seq_string = cpuset_common_read_seq_string,
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.write_string = cpuset_write_resmask,
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.max_write_len = (100U + 6 * MAX_NUMNODES),
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.private = FILE_MEMLIST,
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