From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
cgroup's subsys has "readonly" files, but default permission is always
rw-r--r--. This allows to create r--r--r-- file to subsys.
(The user can do chmod on this read-only file. But this behavior is not
different from current pseudo file systems as /proc.)
Reason:
When I wrote tools for maintain cgroup, I can't find which file is
writable intarfece or not via cgroup file systems. (finally, I did
dirty approach.)
IMHO, showing "this file is read-only" in explicit way is useful
for user-land (tools). In other story, a file whose name sounds read-only
may have "trigger" operation and support reseting. In this case,
"writable" is informative.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
include/linux/cgroup.h | 2 ++
kernel/cgroup.c | 5 ++++-
2 files changed, 6 insertions(+), 1 deletion(-)
Index: mmotm-2.6.29-Feb24/include/linux/cgroup.h
===================================================================
--- mmotm-2.6.29-Feb24.orig/include/linux/cgroup.h
+++ mmotm-2.6.29-Feb24/include/linux/cgroup.h
@@ -258,6 +258,8 @@ struct cftype {
*/
char name[MAX_CFTYPE_NAME];
int private;
+ /* if not 0, mode is set to mode, otherwise 0644 */
+ int mode;
/*
* If non-zero, defines the maximum length of string that can
Index: mmotm-2.6.29-Feb24/kernel/cgroup.c
===================================================================
--- mmotm-2.6.29-Feb24.orig/kernel/cgroup.c
+++ mmotm-2.6.29-Feb24/kernel/cgroup.c
@@ -1767,7 +1767,10 @@ int cgroup_add_file(struct cgroup *cgrp,
BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
dentry = lookup_one_len(name, dir, strlen(name));
if (!IS_ERR(dentry)) {
- error = cgroup_create_file(dentry, 0644 | S_IFREG,
+ int mode = 0644;
+ if (cft->mode)
+ mode = cft->mode;
+ error = cgroup_create_file(dentry, mode | S_IFREG,
cgrp->root->sb);
if (!error)
dentry->d_fsdata = (void *)cft;
_______________________________________________
Containers mailing list
Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linux-foundation.org/mailman/listinfo/containers
