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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Li Zefan · Linus Torvalds
1 parent b6719ec1ad
Showing 3 changed files with 40 additions and 4 deletions Side-by-side Diff
include/linux/cgroup.h
kernel/cgroup.c
kernel/cpuset.c
@@ -258,6 +258,11 @@
 	 */
 	char name[MAX_CFTYPE_NAME];
 	int private;
+	/*
+	 * If not 0, file mode is set to this value, otherwise it will
+	 * be figured out automatically
+	 */
+	mode_t mode;
  
 	/*
 	 * If non-zero, defines the maximum length of string that can
@@ -1686,7 +1686,7 @@
 	.rename = cgroup_rename,
 };
  
-static int cgroup_create_file(struct dentry *dentry, int mode,
+static int cgroup_create_file(struct dentry *dentry, mode_t mode,
 				struct super_block *sb)
 {
 	static const struct dentry_operations cgroup_dops = {
@@ -1732,7 +1732,7 @@
  * @mode: mode to set on new directory.
  */
 static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
-				int mode)
+				mode_t mode)
 {
 	struct dentry *parent;
 	int error = 0;
@@ -1750,6 +1750,33 @@
 	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 S_IRUGO|S_IWUSR if it has both a read and a write handler
+ * returns S_IRUGO if it has only a read handler
+ * returns S_IWUSR if it has only a write hander
+ */
+static mode_t cgroup_file_mode(const struct cftype *cft)
+{
+	mode_t 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 |= S_IRUGO;
+
+	if (cft->write || cft->write_u64 || cft->write_s64 ||
+	    cft->write_string || cft->trigger)
+		mode |= S_IWUSR;
+
+	return mode;
+}
+
 int cgroup_add_file(struct cgroup *cgrp,
 		       struct cgroup_subsys *subsys,
 		       const struct cftype *cft)
@@ -1757,6 +1784,7 @@
 	struct dentry *dir = cgrp->dentry;
 	struct dentry *dentry;
 	int error;
+	mode_t 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 @@
 	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 @@
 		.write_u64 = cgroup_tasks_write,
 		.release = cgroup_tasks_release,
 		.private = FILE_TASKLIST,
+		.mode = S_IRUGO | S_IWUSR,
 	},
  
 	{
@@ -2449,7 +2479,7 @@
  * Must be called with the mutex on the parent inode held
  */
 static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
-			     int mode)
+			     mode_t mode)
 {
 	struct cgroup *cgrp;
 	struct cgroupfs_root *root = parent->root;
@@ -1706,6 +1706,7 @@
 		.read_u64 = cpuset_read_u64,
 		.write_u64 = cpuset_write_u64,
 		.private = FILE_MEMORY_PRESSURE,
+		.mode = S_IRUGO,
 	},
  
 	{
...	...	@@ -258,6 +258,11 @@
258	258	*/
259	259	char name[MAX_CFTYPE_NAME];
260	260	int private;
	261	+ /*
	262	+ * If not 0, file mode is set to this value, otherwise it will
	263	+ * be figured out automatically
	264	+ */
	265	+ mode_t mode;
261	266
262	267	/*
263	268	* If non-zero, defines the maximum length of string that can
...	...	@@ -1686,7 +1686,7 @@
1686	1686	.rename = cgroup_rename,
1687	1687	};
1688	1688
1689		-static int cgroup_create_file(struct dentry *dentry, int mode,
	1689	+static int cgroup_create_file(struct dentry *dentry, mode_t mode,
1690	1690	struct super_block *sb)
1691	1691	{
1692	1692	static const struct dentry_operations cgroup_dops = {
...	...	@@ -1732,7 +1732,7 @@
1732	1732	* @mode: mode to set on new directory.
1733	1733	*/
1734	1734	static int cgroup_create_dir(struct cgroup cgrp, struct dentry dentry,
1735		- int mode)
	1735	+ mode_t mode)
1736	1736	{
1737	1737	struct dentry *parent;
1738	1738	int error = 0;
...	...	@@ -1750,6 +1750,33 @@
1750	1750	return error;
1751	1751	}
1752	1752
	1753	+/**
	1754	+ * cgroup_file_mode - deduce file mode of a control file
	1755	+ * @cft: the control file in question
	1756	+ *
	1757	+ * returns cft->mode if ->mode is not 0
	1758	+ * returns S_IRUGO\|S_IWUSR if it has both a read and a write handler
	1759	+ * returns S_IRUGO if it has only a read handler
	1760	+ * returns S_IWUSR if it has only a write hander
	1761	+ */
	1762	+static mode_t cgroup_file_mode(const struct cftype *cft)
	1763	+{
	1764	+ mode_t mode = 0;
	1765	+
	1766	+ if (cft->mode)
	1767	+ return cft->mode;
	1768	+
	1769	+ if (cft->read \|\| cft->read_u64 \|\| cft->read_s64 \|\|
	1770	+ cft->read_map \|\| cft->read_seq_string)
	1771	+ mode \|= S_IRUGO;
	1772	+
	1773	+ if (cft->write \|\| cft->write_u64 \|\| cft->write_s64 \|\|
	1774	+ cft->write_string \|\| cft->trigger)
	1775	+ mode \|= S_IWUSR;
	1776	+
	1777	+ return mode;
	1778	+}
	1779	+
1753	1780	int cgroup_add_file(struct cgroup *cgrp,
1754	1781	struct cgroup_subsys *subsys,
1755	1782	const struct cftype *cft)
...	...	@@ -1757,6 +1784,7 @@
1757	1784	struct dentry *dir = cgrp->dentry;
1758	1785	struct dentry *dentry;
1759	1786	int error;
	1787	+ mode_t mode;
1760	1788
1761	1789	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
1762	1790	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
...	...	@@ -1767,7 +1795,8 @@
1767	1795	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
1768	1796	dentry = lookup_one_len(name, dir, strlen(name));
1769	1797	if (!IS_ERR(dentry)) {
1770		- error = cgroup_create_file(dentry, 0644 \| S_IFREG,
	1798	+ mode = cgroup_file_mode(cft);
	1799	+ error = cgroup_create_file(dentry, mode \| S_IFREG,
1771	1800	cgrp->root->sb);
1772	1801	if (!error)
1773	1802	dentry->d_fsdata = (void *)cft;
...	...	@@ -2349,6 +2378,7 @@
2349	2378	.write_u64 = cgroup_tasks_write,
2350	2379	.release = cgroup_tasks_release,
2351	2380	.private = FILE_TASKLIST,
	2381	+ .mode = S_IRUGO \| S_IWUSR,
2352	2382	},
2353	2383
2354	2384	{
...	...	@@ -2449,7 +2479,7 @@
2449	2479	* Must be called with the mutex on the parent inode held
2450	2480	*/
2451	2481	static long cgroup_create(struct cgroup parent, struct dentry dentry,
2452		- int mode)
	2482	+ mode_t mode)
2453	2483	{
2454	2484	struct cgroup *cgrp;
2455	2485	struct cgroupfs_root *root = parent->root;
...	...	@@ -1706,6 +1706,7 @@
1706	1706	.read_u64 = cpuset_read_u64,
1707	1707	.write_u64 = cpuset_write_u64,
1708	1708	.private = FILE_MEMORY_PRESSURE,
	1709	+ .mode = S_IRUGO,
1709	1710	},
1710	1711
1711	1712	{