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cgroup: unify read path so that seq_file is always used

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With the recent removal of cftype->read() and ->read_map(), only three
operations are remaining, ->read_u64(), ->read_s64() and
->read_seq_string().  Currently, the first two are handled directly
while the last is handled through seq_file.

It is trivial to serve the first two through the seq_file path too.
This patch restructures read path so that all operations are served
through cgroup_seqfile_show().  This makes all cgroup files seq_file -
single_open/release() are now used by default,
cgroup_seqfile_operations is dropped, and cgroup_file_operations uses
seq_read() for read.

This simplifies the code and makes the read path easy to convert to
use kernfs.

Note that, while cgroup_file_operations uses seq_read() for read, it
still uses generic_file_llseek() for seeking instead of seq_lseek().
This is different from cgroup_seqfile_operations but shouldn't break
anything and brings the seeking behavior aligned with kernfs.

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 12:28:04 -05:00
parent a742c59de6
commit 896f519963
1 changed files with 15 additions and 53 deletions
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68
kernel/cgroup.c
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@ -2295,42 +2295,6 @@ out_free:
return ret ?: nbytes;
}
static ssize_t cgroup_read_u64(struct cgroup_subsys_state *css,
struct cftype *cft, struct file *file,
char __user *buf, size_t nbytes, loff_t *ppos)
{
char tmp[CGROUP_LOCAL_BUFFER_SIZE];
u64 val = cft->read_u64(css, cft);
int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
}
static ssize_t cgroup_read_s64(struct cgroup_subsys_state *css,
struct cftype *cft, struct file *file,
char __user *buf, size_t nbytes, loff_t *ppos)
{
char tmp[CGROUP_LOCAL_BUFFER_SIZE];
s64 val = cft->read_s64(css, cft);
int len = sprintf(tmp, "%lld\n", (long long) val);
return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
}
static ssize_t cgroup_file_read(struct file *file, char __user *buf,
size_t nbytes, loff_t *ppos)
{
struct cfent *cfe = __d_cfe(file->f_dentry);
struct cftype *cft = __d_cft(file->f_dentry);
struct cgroup_subsys_state *css = cfe->css;
if (cft->read_u64)
return cgroup_read_u64(css, cft, file, buf, nbytes, ppos);
if (cft->read_s64)
return cgroup_read_s64(css, cft, file, buf, nbytes, ppos);
return -EINVAL;
}
/*
* seqfile ops/methods for returning structured data. Currently just
* supports string->u64 maps, but can be extended in future.
@ -2342,15 +2306,17 @@ static int cgroup_seqfile_show(struct seq_file *m, void *arg)
struct cftype *cft = cfe->type;
struct cgroup_subsys_state *css = cfe->css;
return cft->read_seq_string(css, cft, m);
}
if (cft->read_seq_string)
return cft->read_seq_string(css, cft, m);
static const struct file_operations cgroup_seqfile_operations = {
.read = seq_read,
.write = cgroup_file_write,
.llseek = seq_lseek,
.release = cgroup_file_release,
};
if (cft->read_u64)
seq_printf(m, "%llu\n", cft->read_u64(css, cft));
else if (cft->read_s64)
seq_printf(m, "%lld\n", cft->read_s64(css, cft));
else
return -EINVAL;
return 0;
}
static int cgroup_file_open(struct inode *inode, struct file *file)
{
@ -2387,12 +2353,10 @@ static int cgroup_file_open(struct inode *inode, struct file *file)
WARN_ON_ONCE(cfe->css && cfe->css != css);
cfe->css = css;
if (cft->read_seq_string) {
file->f_op = &cgroup_seqfile_operations;
err = single_open(file, cgroup_seqfile_show, cfe);
} else if (cft->open) {
if (cft->open)
err = cft->open(inode, file);
}
else
err = single_open(file, cgroup_seqfile_show, cfe);
if (css->ss && err)
css_put(css);
@ -2406,9 +2370,7 @@ static int cgroup_file_release(struct inode *inode, struct file *file)
if (css->ss)
css_put(css);
if (file->f_op == &cgroup_seqfile_operations)
single_release(inode, file);
return 0;
return single_release(inode, file);
}
/*
@ -2519,7 +2481,7 @@ static ssize_t cgroup_listxattr(struct dentry *dentry, char *buf, size_t size)
}
static const struct file_operations cgroup_file_operations = {
.read = cgroup_file_read,
.read = seq_read,
.write = cgroup_file_write,
.llseek = generic_file_llseek,
.open = cgroup_file_open,