linux-kernel - [PATCH] cpuset decrustify update and validate masks

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Date:	Sun, 30 Sep 2007 03:44:09 -0700
From:	Paul Jackson <pj@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	nickpiggin@...oo.com.au, Paul Menage <menage@...gle.com>,
	linux-kernel@...r.kernel.org,
	Dinakar Guniguntala <dino@...ibm.com>,
	Paul Jackson <pj@....com>, cpw@....com,
	Ingo Molnar <mingo@...e.hu>
Subject: [PATCH] cpuset decrustify update and validate masks

From: Paul Jackson <pj@....com>

The kernel/cpuset.c code handling the updating of a cpusets
'cpus' and 'mems' masks was starting to look a little bit
crufty to me.

So I rewrote it a little bit.  Other than subtle improvements
in the consistency of identifying white space at the beginning
and end of passed in masks, I don't see that it makes any
visible difference in behaviour.  But it's one or two hundred
kernel text bytes smaller, and to my eye, easier to understand.

Signed-off-by: Paul Jackson <pj@....com>

---

Andrew - this patch goes after:
  cpuset-and-sched-domains-sched_load_balance-flag

 kernel/cpuset.c |   50 ++++++++++++++++++++------------------------------
 1 file changed, 20 insertions(+), 30 deletions(-)

--- 2.6.23-rc8-mm1.orig/kernel/cpuset.c	2007-09-30 01:27:28.442825126 -0700
+++ 2.6.23-rc8-mm1/kernel/cpuset.c	2007-09-30 01:38:22.829256421 -0700
@@ -488,6 +488,14 @@ static int validate_change(const struct 
 			return -EINVAL;
 	}
 
+	/* Cpusets with tasks can't have empty cpus_allowed or mems_allowed */
+	if (cgroup_task_count(cur->css.cgroup)) {
+		if (cpus_empty(trial->cpus_allowed) ||
+	    	    nodes_empty(trial->mems_allowed)) {
+			return -ENOSPC;
+		}
+	}
+
 	return 0;
 }
 
@@ -691,11 +699,13 @@ static int update_cpumask(struct cpuset 
 	trialcs = *cs;
 
 	/*
-	 * We allow a cpuset's cpus_allowed to be empty; if it has attached
-	 * tasks, we'll catch it later when we validate the change and return
-	 * -ENOSPC.
+	 * An empty cpus_allowed is ok iff there are no tasks in the cpuset.
+	 * Since cpulist_parse() fails on an empty mask, we special case
+	 * that parsing.  The validate_change() call ensures that cpusets
+	 * with tasks have cpus.
 	 */
-	if (!buf[0] || (buf[0] == '\n' && !buf[1])) {
+	buf = strstrip(buf);
+	if (!*buf) {
 		cpus_clear(trialcs.cpus_allowed);
 	} else {
 		retval = cpulist_parse(buf, trialcs.cpus_allowed);
@@ -703,10 +713,6 @@ static int update_cpumask(struct cpuset 
 			return retval;
 	}
 	cpus_and(trialcs.cpus_allowed, trialcs.cpus_allowed, cpu_online_map);
-	/* cpus_allowed cannot be empty for a cpuset with attached tasks. */
-	if (cgroup_task_count(cs->css.cgroup) &&
-	    cpus_empty(trialcs.cpus_allowed))
-		return -ENOSPC;
 	retval = validate_change(cs, &trialcs);
 	if (retval < 0)
 		return retval;
@@ -811,29 +817,19 @@ static int update_nodemask(struct cpuset
 	trialcs = *cs;
 
 	/*
-	 * We allow a cpuset's mems_allowed to be empty; if it has attached
-	 * tasks, we'll catch it later when we validate the change and return
-	 * -ENOSPC.
+	 * An empty mems_allowed is ok iff there are no tasks in the cpuset.
+	 * Since nodelist_parse() fails on an empty mask, we special case
+	 * that parsing.  The validate_change() call ensures that cpusets
+	 * with tasks have memory.
 	 */
-	if (!buf[0] || (buf[0] == '\n' && !buf[1])) {
+	buf = strstrip(buf);
+	if (!*buf) {
 		nodes_clear(trialcs.mems_allowed);
 	} else {
 		retval = nodelist_parse(buf, trialcs.mems_allowed);
 		if (retval < 0)
 			goto done;
-		if (!nodes_intersects(trialcs.mems_allowed,
-						node_states[N_HIGH_MEMORY])) {
-			/*
-			 * error if only memoryless nodes specified.
-			 */
-			retval = -ENOSPC;
-			goto done;
-		}
 	}
-	/*
-	 * Exclude memoryless nodes.  We know that trialcs.mems_allowed
-	 * contains at least one node with memory.
-	 */
 	nodes_and(trialcs.mems_allowed, trialcs.mems_allowed,
 						node_states[N_HIGH_MEMORY]);
 	oldmem = cs->mems_allowed;
@@ -841,12 +837,6 @@ static int update_nodemask(struct cpuset
 		retval = 0;		/* Too easy - nothing to do */
 		goto done;
 	}
-	/* mems_allowed cannot be empty for a cpuset with attached tasks. */
-	if (cgroup_task_count(cs->css.cgroup) &&
-	    nodes_empty(trialcs.mems_allowed)) {
-		retval = -ENOSPC;
-		goto done;
-	}
 	retval = validate_change(cs, &trialcs);
 	if (retval < 0)
 		goto done;

-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <pj@....com> 1.650.933.1373
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