[Devel] [PATCH 3/3] make 'none' field a flag

[Glauber Costa]

There is no reason to have a flags field, and then a separate
bool field just to indicate if 'none' subsystem were explicitly
requested.

Make it a flag

Signed-off-by: Glauber Costa <glommer at parallels.com>
---
 kernel/cgroup.c |   20 ++++++++++++--------
 1 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index fa405ee..e700abe 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -232,6 +232,7 @@ inline int cgroup_is_removed(const struct cgroup *cgrp)
 enum {
 	ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
 	ROOT_CLONE_CHILDREN, /* mounted subsystems starts with clone_children */
+	ROOT_NOSUBSYS, /* explicitly asked for 'none' subsystems */
 };
 
 static int cgroup_is_releasable(const struct cgroup *cgrp)
@@ -1064,13 +1065,16 @@ struct cgroup_sb_opts {
 	unsigned long flags;
 	char *release_agent;
 	char *name;
-	/* User explicitly requested empty subsystem */
-	bool none;
 
 	struct cgroupfs_root *new_root;
 
 };
 
+static inline int opts_no_subsys(const struct cgroup_sb_opts *opts)
+{
+	return test_bit(ROOT_NOSUBSYS, &opts->flags);
+}
+
 /*
  * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
  * with cgroup_mutex held to protect the subsys[] array. This function takes
@@ -1098,7 +1102,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 			return -EINVAL;
 		if (!strcmp(token, "none")) {
 			/* Explicitly have no subsystems */
-			opts->none = true;
+			set_bit(ROOT_NOSUBSYS, &opts->flags);
 			continue;
 		}
 		if (!strcmp(token, "all")) {
@@ -1178,7 +1182,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 	 * otherwise 'all, 'none' and a subsystem name options were not
 	 * specified, let's default to 'all'
 	 */
-	if (all_ss || (!all_ss && !one_ss && !opts->none)) {
+	if (all_ss || (!all_ss && !one_ss && !opts_no_subsys(opts))) {
 		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
 			struct cgroup_subsys *ss = subsys[i];
 			if (ss == NULL)
@@ -1202,7 +1206,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 
 
 	/* Can't specify "none" and some subsystems */
-	if (opts->subsys_bits && opts->none)
+	if (opts->subsys_bits && opts_no_subsys(opts))
 		return -EINVAL;
 
 	/*
@@ -1370,7 +1374,7 @@ static int cgroup_test_super(struct super_block *sb, void *data)
 	 * If we asked for subsystems (or explicitly for no
 	 * subsystems) then they must match
 	 */
-	if ((opts->subsys_bits || opts->none)
+	if ((opts->subsys_bits || opts_no_subsys(opts))
 	    && (opts->subsys_bits != root->subsys_bits))
 		return 0;
 
@@ -1381,7 +1385,7 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
 {
 	struct cgroupfs_root *root;
 
-	if (!opts->subsys_bits && !opts->none)
+	if (!opts->subsys_bits && !opts_no_subsys(opts))
 		return NULL;
 
 	root = kzalloc(sizeof(*root), GFP_KERNEL);
@@ -1426,7 +1430,7 @@ static int cgroup_set_super(struct super_block *sb, void *data)
 	if (!opts->new_root)
 		return -EINVAL;
 
-	BUG_ON(!opts->subsys_bits && !opts->none);
+	BUG_ON(!opts->subsys_bits && !opts_no_subsys(opts));
 
 	ret = set_anon_super(sb, NULL);
 	if (ret)
-- 
1.7.6.4