cgroups: misc cleanups to write_string patchset
This patch contains cleanups suggested by reviewers for the recent
write_string() patchset:
- pair cgroup_lock_live_group() with cgroup_unlock() in cgroup.c for
clarity, rather than directly unlocking cgroup_mutex.
- make the return type of cgroup_lock_live_group() a bool
- use a #define'd constant for the local buffer size in read/write functions
Signed-off-by: Paul Menage <menage@google.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: 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>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 0120b5d..a14122e 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1329,10 +1329,10 @@
* cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
* @cgrp: the cgroup to be checked for liveness
*
- * Returns true (with lock held) on success, or false (with no lock
- * held) on failure.
+ * On success, returns true; the lock should be later released with
+ * cgroup_unlock(). On failure returns false with no lock held.
*/
-int cgroup_lock_live_group(struct cgroup *cgrp)
+bool cgroup_lock_live_group(struct cgroup *cgrp)
{
mutex_lock(&cgroup_mutex);
if (cgroup_is_removed(cgrp)) {
@@ -1349,7 +1349,7 @@
if (!cgroup_lock_live_group(cgrp))
return -ENODEV;
strcpy(cgrp->root->release_agent_path, buffer);
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
return 0;
}
@@ -1360,16 +1360,19 @@
return -ENODEV;
seq_puts(seq, cgrp->root->release_agent_path);
seq_putc(seq, '\n');
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
return 0;
}
+/* A buffer size big enough for numbers or short strings */
+#define CGROUP_LOCAL_BUFFER_SIZE 64
+
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
struct file *file,
const char __user *userbuf,
size_t nbytes, loff_t *unused_ppos)
{
- char buffer[64];
+ char buffer[CGROUP_LOCAL_BUFFER_SIZE];
int retval = 0;
char *end;
@@ -1403,7 +1406,7 @@
const char __user *userbuf,
size_t nbytes, loff_t *unused_ppos)
{
- char local_buffer[64];
+ char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
int retval = 0;
size_t max_bytes = cft->max_write_len;
char *buffer = local_buffer;
@@ -1518,7 +1521,7 @@
char __user *buf, size_t nbytes,
loff_t *ppos)
{
- char tmp[64];
+ char tmp[CGROUP_LOCAL_BUFFER_SIZE];
u64 val = cft->read_u64(cgrp, cft);
int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
@@ -1530,7 +1533,7 @@
char __user *buf, size_t nbytes,
loff_t *ppos)
{
- char tmp[64];
+ char tmp[CGROUP_LOCAL_BUFFER_SIZE];
s64 val = cft->read_s64(cgrp, cft);
int len = sprintf(tmp, "%lld\n", (long long) val);