linux-kernel - [PATCH 2/3] pids: Split alloc

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Date:	Thu, 10 Nov 2011 21:15:49 +0400
From:	Pavel Emelyanov <xemul@...allels.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Glauber Costa <glommer@...allels.com>,
	Nathan Lynch <ntl@...ox.com>, Tejun Heo <tj@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Serge Hallyn <serue@...ibm.com>,
	Daniel Lezcano <dlezcano@...ibm.com>
Subject: [PATCH 2/3] pids: Split alloc_pidmap into parts

The map's page allocation code is moved to separate function
to make clone-with-pids patching simpler.

Signed-off-by: Pavel Emelyanov <xemul@...allels.com>

---
 kernel/pid.c |   37 ++++++++++++++++++++++---------------
 1 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/kernel/pid.c b/kernel/pid.c
index 2d9704c..700dda3 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -159,6 +159,25 @@ static void set_last_pid(struct pid_namespace *pid_ns, int base, int pid)
 	} while ((prev != last_write) && (pid_before(base, last_write, pid)));
 }
 
+static int alloc_pidmap_page(struct pidmap *map)
+{
+	void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
+
+	/*
+	 * Free the page if someone raced with us
+	 * installing it:
+	 */
+	spin_lock_irq(&pidmap_lock);
+	if (!map->page) {
+		map->page = page;
+		page = NULL;
+	}
+	spin_unlock_irq(&pidmap_lock);
+	kfree(page);
+
+	return map->page ? 0 : -1;
+}
+
 static int alloc_pidmap(struct pid_namespace *pid_ns)
 {
 	int i, offset, max_scan, pid, last = pid_ns->last_pid;
@@ -176,22 +195,10 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
 	 */
 	max_scan = DIV_ROUND_UP(pid_max, BITS_PER_PAGE) - !offset;
 	for (i = 0; i <= max_scan; ++i) {
-		if (unlikely(!map->page)) {
-			void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
-			/*
-			 * Free the page if someone raced with us
-			 * installing it:
-			 */
-			spin_lock_irq(&pidmap_lock);
-			if (!map->page) {
-				map->page = page;
-				page = NULL;
-			}
-			spin_unlock_irq(&pidmap_lock);
-			kfree(page);
-			if (unlikely(!map->page))
+		if (unlikely(!map->page))
+			if (alloc_pidmap_page(map))
 				break;
-		}
+
 		if (likely(atomic_read(&map->nr_free))) {
 			do {
 				if (!test_and_set_bit(offset, map->page)) {
-- 
1.5.5.6
--
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