[PATCH] cgroups: show correct file mode

[Li Zefan <lizf@cn.fujitsu.com>]

Andrew, please drop these 2 patches:
  cgroup-allow-subsys-to-set-default-mode-of-its-own-file.patch
  cgroup-memcg-show-correct-file-mode.patch

Here is a patch to replace them.


=============


From: Li Zefan <lizf@cn.fujitsu.com>
Date: Tue, 3 Mar 2009 08:55:58 +0800
Subject: [PATCH] cgroups: show correct file mode

We have some read-only files and write-only files, but currently they
are all set to 0644, which is counter-intuitive and cause trouble
for some cgroup tools like libcgroup.

This patch adds 'mode' to struct cftype to allow cgroup subsys to set
it's own files' file mode, and for the most cases cft->mode can be
default to 0 and cgroup will figure out proper mode.

Acked-by: Paul Menage <menage@google.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 include/linux/cgroup.h |    5 +++++
 kernel/cgroup.c        |   32 +++++++++++++++++++++++++++++++-
 kernel/cpuset.c        |    1 +
 3 files changed, 37 insertions(+), 1 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 6ad1989..31cc1a9 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -258,6 +258,11 @@ struct cftype {
 	 */
 	char name[MAX_CFTYPE_NAME];
 	int private;
+	/*
+	 * If not 0, file mode is set to this value, otherwise it will
+	 * be figured out automatically
+	 */
+	int mode;
 
 	/*
 	 * If non-zero, defines the maximum length of string that can
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 379baa3..043b24e 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1750,6 +1750,33 @@ static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
 	return error;
 }
 
+/**
+ * cgroup_file_mode - deduce file mode of a control file
+ * @cft: the control file in question
+ *
+ * returns cft->mode if ->mode is not 0
+ * returns 0644 if it has both a read and a write handler
+ * returns 0444 if it has only a read handler
+ * returns 0200 if it has only a write hander
+ */
+static int cgroup_file_mode(const struct cftype *cft)
+{
+	int mode = 0;
+
+	if (cft->mode)
+		return cft->mode;
+
+	if (cft->read || cft->read_u64 || cft->read_s64 ||
+	    cft->read_map || cft->read_seq_string)
+		mode |= 0444;
+
+	if (cft->write || cft->write_u64 || cft->write_s64 ||
+	    cft->write_string || cft->trigger)
+		mode |= 0200;
+
+	return mode;
+}
+
 int cgroup_add_file(struct cgroup *cgrp,
 		       struct cgroup_subsys *subsys,
 		       const struct cftype *cft)
@@ -1757,6 +1784,7 @@ int cgroup_add_file(struct cgroup *cgrp,
 	struct dentry *dir = cgrp->dentry;
 	struct dentry *dentry;
 	int error;
+	int mode;
 
 	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
 	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
@@ -1767,7 +1795,8 @@ 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,
+		mode = cgroup_file_mode(cft);
+		error = cgroup_create_file(dentry, mode | S_IFREG,
 						cgrp->root->sb);
 		if (!error)
 			dentry->d_fsdata = (void *)cft;
@@ -2349,6 +2378,7 @@ static struct cftype files[] = {
 		.write_u64 = cgroup_tasks_write,
 		.release = cgroup_tasks_release,
 		.private = FILE_TASKLIST,
+		.mode = 0644,
 	},
 
 	{
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index a46d693..31e28b3 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1678,6 +1678,7 @@ static struct cftype files[] = {
 		.read_u64 = cpuset_read_u64,
 		.write_u64 = cpuset_write_u64,
 		.private = FILE_MEMORY_PRESSURE,
+		.mode = 0444,
 	},
 
 	{
-- 
1.5.4.rc3