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cpuset: convert away from cftype->read()

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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>
This commit is contained in:
Tejun Heo 2013-12-05 12:28:02 -05:00
parent 44ffc75ba9
commit 51ffe41178
1 changed files with 24 additions and 47 deletions
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71
kernel/cpuset.c
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@ -1731,66 +1731,43 @@ static int cpuset_write_resmask(struct cgroup_subsys_state *css,
* used, list of ranges of sequential numbers, is variable length, * used, list of ranges of sequential numbers, is variable length,
* and since these maps can change value dynamically, one could read * and since these maps can change value dynamically, one could read
* gibberish by doing partial reads while a list was changing. * 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 int cpuset_common_read_seq_string(struct cgroup_subsys_state *css,
static size_t cpuset_sprintf_cpulist(char *page, struct cpuset *cs) struct cftype *cft,
{ struct seq_file *sf)
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)
{ {
struct cpuset *cs = css_cs(css); struct cpuset *cs = css_cs(css);
cpuset_filetype_t type = cft->private; cpuset_filetype_t type = cft->private;
char *page; ssize_t count;
ssize_t retval = 0; char *buf, *s;
char *s; int ret = 0;
if (!(page = (char *)__get_free_page(GFP_TEMPORARY))) count = seq_get_buf(sf, &buf);
return -ENOMEM; s = buf;
s = page; mutex_lock(&callback_mutex);
switch (type) { switch (type) {
case FILE_CPULIST: case FILE_CPULIST:
s += cpuset_sprintf_cpulist(s, cs); s += cpulist_scnprintf(s, count, cs->cpus_allowed);
break; break;
case FILE_MEMLIST: case FILE_MEMLIST:
s += cpuset_sprintf_memlist(s, cs); s += nodelist_scnprintf(s, count, cs->mems_allowed);
break; break;
default: default:
retval = -EINVAL; ret = -EINVAL;
goto out; goto out_unlock;
} }
*s++ = '\n';
retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page); if (s < buf + count - 1) {
out: *s++ = '\n';
free_page((unsigned long)page); seq_commit(sf, s - buf);
return retval; } 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) 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[] = { static struct cftype files[] = {
{ {
.name = "cpus", .name = "cpus",
.read = cpuset_common_file_read, .read_seq_string = cpuset_common_read_seq_string,
.write_string = cpuset_write_resmask, .write_string = cpuset_write_resmask,
.max_write_len = (100U + 6 * NR_CPUS), .max_write_len = (100U + 6 * NR_CPUS),
.private = FILE_CPULIST, .private = FILE_CPULIST,
@ -1855,7 +1832,7 @@ static struct cftype files[] = {
{ {
.name = "mems", .name = "mems",
.read = cpuset_common_file_read, .read_seq_string = cpuset_common_read_seq_string,
.write_string = cpuset_write_resmask, .write_string = cpuset_write_resmask,
.max_write_len = (100U + 6 * MAX_NUMNODES), .max_write_len = (100U + 6 * MAX_NUMNODES),
.private = FILE_MEMLIST, .private = FILE_MEMLIST,