cgroup files: add write_string cgroup control file method

This patch adds a write_string() method for cgroups control files. The
semantics are that a buffer is copied from userspace to kernelspace
and the handler function invoked on that buffer.  The buffer is
guaranteed to be nul-terminated, and no longer than max_write_len
(defaulting to 64 bytes if unspecified). Later patches will convert
existing raw file write handlers in control group subsystems to use
this method.

Signed-off-by: Paul Menage <menage@google.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Balbir Singh <balbir@in.ibm.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Paul Menage 2008-07-25 01:46:58 -07:00 committed by Linus Torvalds
parent ce16b49d37
commit db3b14978a
2 changed files with 49 additions and 0 deletions

View file

@ -205,6 +205,13 @@ struct cftype {
* subsystem, followed by a period */
char name[MAX_CFTYPE_NAME];
int private;
/*
* If non-zero, defines the maximum length of string that can
* be passed to write_string; defaults to 64
*/
size_t max_write_len;
int (*open)(struct inode *inode, struct file *file);
ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
struct file *file,
@ -248,6 +255,13 @@ struct cftype {
*/
int (*write_s64)(struct cgroup *cgrp, struct cftype *cft, s64 val);
/*
* write_string() is passed a nul-terminated kernelspace
* buffer of maximum length determined by max_write_len.
* Returns 0 or -ve error code.
*/
int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
const char *buffer);
/*
* trigger() callback can be used to get some kick from the
* userspace, when the actual string written is not important