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Commit 51ffe411 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 44ffc75b

kernel/cpuset.c

+24 −47
Original line number Diff line number Diff line
@@ -1731,66 +1731,43 @@ static int cpuset_write_resmask(struct cgroup_subsys_state *css, 
 * used, list of ranges of sequential numbers, is variable length,

 * and since these maps can change value dynamically, one could read

 * gibberish by doing partial reads while a list was changing.

 * A single large read to a buffer that crosses a page boundary is

 * ok, because the result being copied to user land is not recomputed

 * across a page fault.

 */



static size_t cpuset_sprintf_cpulist(char *page, struct cpuset *cs)

{

	size_t count;



	mutex_lock(&callback_mutex);

	count = cpulist_scnprintf(page, PAGE_SIZE, cs->cpus_allowed);

	mutex_unlock(&callback_mutex);



	return count;

}



static size_t cpuset_sprintf_memlist(char *page, struct cpuset *cs)

{

	size_t count;



	mutex_lock(&callback_mutex);

	count = nodelist_scnprintf(page, PAGE_SIZE, cs->mems_allowed);

	mutex_unlock(&callback_mutex);



	return count;

}



static ssize_t cpuset_common_file_read(struct cgroup_subsys_state *css,

				       struct cftype *cft, struct file *file,

				       char __user *buf, size_t nbytes,

				       loff_t *ppos)

static int cpuset_common_read_seq_string(struct cgroup_subsys_state *css,

					 struct cftype *cft,

					 struct seq_file *sf)

{

	struct cpuset *cs = css_cs(css);

	cpuset_filetype_t type = cft->private;

	char *page;

	ssize_t retval = 0;

	char *s;

	ssize_t count;

	char *buf, *s;

	int ret = 0;



	if (!(page = (char *)__get_free_page(GFP_TEMPORARY)))

		return -ENOMEM;

	count = seq_get_buf(sf, &buf);

	s = buf;



	s = page;

	mutex_lock(&callback_mutex);



	switch (type) {

	case FILE_CPULIST:

		s += cpuset_sprintf_cpulist(s, cs);

		s += cpulist_scnprintf(s, count, cs->cpus_allowed);

		break;

	case FILE_MEMLIST:

		s += cpuset_sprintf_memlist(s, cs);

		s += nodelist_scnprintf(s, count, cs->mems_allowed);

		break;

	default:

		retval = -EINVAL;

		goto out;

		ret = -EINVAL;

		goto out_unlock;

	}

	*s++ = '\n';



	retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page);

out:

	free_page((unsigned long)page);

	return retval;

	if (s < buf + count - 1) {

		*s++ = '\n';

		seq_commit(sf, s - buf);

	} else {

		seq_commit(sf, -1);

	}

out_unlock:

	mutex_unlock(&callback_mutex);

	return ret;

}



static u64 cpuset_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
@@ -1847,7 +1824,7 @@ static s64 cpuset_read_s64(struct cgroup_subsys_state *css, struct cftype *cft) 
static struct cftype files[] = {

	{

		.name = "cpus",

		.read = cpuset_common_file_read,

		.read_seq_string = cpuset_common_read_seq_string,

		.write_string = cpuset_write_resmask,

		.max_write_len = (100U + 6 * NR_CPUS),

		.private = FILE_CPULIST,
@@ -1855,7 +1832,7 @@ static struct cftype files[] = { 


	{

		.name = "mems",

		.read = cpuset_common_file_read,

		.read_seq_string = cpuset_common_read_seq_string,

		.write_string = cpuset_write_resmask,

		.max_write_len = (100U + 6 * MAX_NUMNODES),

		.private = FILE_MEMLIST,