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From: Oren Laadan on 17 Mar 2010 12:00
From: Sukadev Bhattiprolu <sukadev(a)linux.vnet.ibm.com>

To simplify alloc_pidmap(), move code to allocate a pid map page to a
separate function.

Changelog[v4]:
- [Oren Laadan] Adapt to kernel 2.6.33-rc5
Changelog[v3]:
- Earlier version of patchset called alloc_pidmap_page() from two
places. But now its called from only one place. Even so, moving
this code out into a separate function simplifies alloc_pidmap().
Changelog[v2]:
- (Matt Helsley, Dave Hansen) Have alloc_pidmap_page() return
-ENOMEM on error instead of -1.

Signed-off-by: Sukadev Bhattiprolu <sukadev(a)linux.vnet.ibm.com>
Acked-by: Serge E. Hallyn <serue(a)us.ibm.com>
Tested-by: Serge E. Hallyn <serue(a)us.ibm.com>
Reviewed-by: Oren Laadan <orenl(a)cs.columbia.edu>
---
kernel/pid.c | 41 ++++++++++++++++++++++++++---------------
1 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/kernel/pid.c b/kernel/pid.c
index 2e17c9c..39292e6 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -122,6 +122,30 @@ static void free_pidmap(struct upid *upid)
atomic_inc(&map->nr_free);
}

+static int alloc_pidmap_page(struct pidmap *map)
+{
+ void *page;
+
+ if (likely(map->page))
+ return 0;
+
+ 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))
+ return -1;
+
+ return 0;
+}
+
static int alloc_pidmap(struct pid_namespace *pid_ns)
{
int i, offset, max_scan, pid, last = pid_ns->last_pid;
@@ -134,22 +158,9 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
max_scan = (pid_max + BITS_PER_PAGE - 1)/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) < 0)
break;
- }
if (likely(atomic_read(&map->nr_free))) {
do {
if (!test_and_set_bit(offset, map->page)) {
--
1.6.3.3

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