[Devel] [PATCH 6/8] CGroup Files: Remove cpuset_common_file_write()

[menage at google.com]

This patch tweaks the signatures of the update_cpumask() and
update_nodemask() functions so that they can be called directly as
handlers for the new cgroups write_string() method.

This allows cpuset_common_file_write() to be removed.

Signed-off-by: Paul Menage <menage at google.com>

---

 This patch fails checkpatch.pl which objects to the use of
NR_CPUS. It's not clear that there's a way to express this more
cleanly, other than leaving it empty and initializing it early in the
boot process.

 kernel/cpuset.c |  109 +++++++++++++++++---------------------------------------
 1 file changed, 35 insertions(+), 74 deletions(-)

Index: cws-2.6.26-rc5-mm3/kernel/cpuset.c
===================================================================
--- cws-2.6.26-rc5-mm3.orig/kernel/cpuset.c
+++ cws-2.6.26-rc5-mm3/kernel/cpuset.c
@@ -227,10 +227,6 @@ static struct cpuset top_cpuset = {
  * The task_struct fields mems_allowed and mems_generation may only
  * be accessed in the context of that task, so require no locks.
  *
- * The cpuset_common_file_write handler for operations that modify
- * the cpuset hierarchy holds cgroup_mutex across the entire operation,
- * single threading all such cpuset modifications across the system.
- *
  * The cpuset_common_file_read() handlers only hold callback_mutex across
  * small pieces of code, such as when reading out possibly multi-word
  * cpumasks and nodemasks.
@@ -801,7 +797,7 @@ static int update_tasks_cpumask(struct c
  * @cs: the cpuset to consider
  * @buf: buffer of cpu numbers written to this cpuset
  */
-static int update_cpumask(struct cpuset *cs, char *buf)
+static int update_cpumask(struct cpuset *cs, const char *buf)
 {
 	struct cpuset trialcs;
 	int retval;
@@ -819,7 +815,6 @@ static int update_cpumask(struct cpuset 
 	 * that parsing.  The validate_change() call ensures that cpusets
 	 * with tasks have cpus.
 	 */
-	buf = strstrip(buf);
 	if (!*buf) {
 		cpus_clear(trialcs.cpus_allowed);
 	} else {
@@ -1016,7 +1011,7 @@ done:
  * lock each such tasks mm->mmap_sem, scan its vma's and rebind
  * their mempolicies to the cpusets new mems_allowed.
  */
-static int update_nodemask(struct cpuset *cs, char *buf)
+static int update_nodemask(struct cpuset *cs, const char *buf)
 {
 	struct cpuset trialcs;
 	nodemask_t oldmem;
@@ -1037,7 +1032,6 @@ static int update_nodemask(struct cpuset
 	 * that parsing.  The validate_change() call ensures that cpusets
 	 * with tasks have memory.
 	 */
-	buf = strstrip(buf);
 	if (!*buf) {
 		nodes_clear(trialcs.mems_allowed);
 	} else {
@@ -1280,72 +1274,14 @@ typedef enum {
 	FILE_SPREAD_SLAB,
 } cpuset_filetype_t;
 
-static ssize_t cpuset_common_file_write(struct cgroup *cont,
-					struct cftype *cft,
-					struct file *file,
-					const char __user *userbuf,
-					size_t nbytes, loff_t *unused_ppos)
-{
-	struct cpuset *cs = cgroup_cs(cont);
-	cpuset_filetype_t type = cft->private;
-	char *buffer;
-	int retval = 0;
-
-	/* Crude upper limit on largest legitimate cpulist user might write. */
-	if (nbytes > 100U + 6 * max(NR_CPUS, MAX_NUMNODES))
-		return -E2BIG;
-
-	/* +1 for nul-terminator */
-	buffer = kmalloc(nbytes + 1, GFP_KERNEL);
-	if (!buffer)
-		return -ENOMEM;
-
-	if (copy_from_user(buffer, userbuf, nbytes)) {
-		retval = -EFAULT;
-		goto out1;
-	}
-	buffer[nbytes] = 0;	/* nul-terminate */
-
-	cgroup_lock();
-
-	if (cgroup_is_removed(cont)) {
-		retval = -ENODEV;
-		goto out2;
-	}
-
-	switch (type) {
-	case FILE_CPULIST:
-		retval = update_cpumask(cs, buffer);
-		break;
-	case FILE_MEMLIST:
-		retval = update_nodemask(cs, buffer);
-		break;
-	default:
-		retval = -EINVAL;
-		goto out2;
-	}
-
-	if (retval == 0)
-		retval = nbytes;
-out2:
-	cgroup_unlock();
-out1:
-	kfree(buffer);
-	return retval;
-}
-
 static int cpuset_write_u64(struct cgroup *cgrp, struct cftype *cft, u64 val)
 {
 	int retval = 0;
 	struct cpuset *cs = cgroup_cs(cgrp);
 	cpuset_filetype_t type = cft->private;
 
-	cgroup_lock();
-
-	if (cgroup_is_removed(cgrp)) {
-		cgroup_unlock();
+	if (!cgroup_lock_live_group(cgrp))
 		return -ENODEV;
-	}
 
 	switch (type) {
 	case FILE_CPU_EXCLUSIVE:
@@ -1391,12 +1327,9 @@ static int cpuset_write_s64(struct cgrou
 	struct cpuset *cs = cgroup_cs(cgrp);
 	cpuset_filetype_t type = cft->private;
 
-	cgroup_lock();
-
-	if (cgroup_is_removed(cgrp)) {
-		cgroup_unlock();
+	if (!cgroup_lock_live_group(cgrp))
 		return -ENODEV;
-	}
+
 	switch (type) {
 	case FILE_SCHED_RELAX_DOMAIN_LEVEL:
 		retval = update_relax_domain_level(cs, val);
@@ -1410,6 +1343,32 @@ static int cpuset_write_s64(struct cgrou
 }
 
 /*
+ * Common handling for a write to a "cpus" or "mems" file.
+ */
+static int cpuset_write_resmask(struct cgroup *cgrp, struct cftype *cft,
+				const char *buf)
+{
+	int retval = 0;
+
+	if (!cgroup_lock_live_group(cgrp))
+		return -ENODEV;
+
+	switch (cft->private) {
+	case FILE_CPULIST:
+		retval = update_cpumask(cgroup_cs(cgrp), buf);
+		break;
+	case FILE_MEMLIST:
+		retval = update_nodemask(cgroup_cs(cgrp), buf);
+		break;
+	default:
+		retval = -EINVAL;
+		break;
+	}
+	cgroup_unlock();
+	return retval;
+}
+
+/*
  * These ascii lists should be read in a single call, by using a user
  * buffer large enough to hold the entire map.  If read in smaller
  * chunks, there is no guarantee of atomicity.  Since the display format
@@ -1528,14 +1487,16 @@ static struct cftype files[] = {
 	{
 		.name = "cpus",
 		.read = cpuset_common_file_read,
-		.write = cpuset_common_file_write,
+		.write_string = cpuset_write_resmask,
+		.max_write_len = (100U + 6 * NR_CPUS),
 		.private = FILE_CPULIST,
 	},
 
 	{
 		.name = "mems",
 		.read = cpuset_common_file_read,
-		.write = cpuset_common_file_write,
+		.write_string = cpuset_write_resmask,
+		.max_write_len = (100U + 6 * MAX_NUMNODES),
 		.private = FILE_MEMLIST,
 	},
 

--
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