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@xxxxxxxxxx>
---
kernel/cgroup.c | 68 +++++++++++++--------------------------------------------
1 file changed, 15 insertions(+), 53 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 23abe8e..7048e7f 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -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,
--
1.8.4.2
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