Subject: [RFC][v8][PATCH 1/10]: Factor out code to allocate pidmap page
To simplify alloc_pidmap(), move code to allocate a pid map page to a
separate function.
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@xxxxxxxxxxxxxxxxxx>
Acked-by: Serge Hallyn <serue@xxxxxxxxxx>
Reviewed-by: Oren Laadan <orenl@xxxxxxxxxxxxxxx>
---
kernel/pid.c | 45 ++++++++++++++++++++++++++++++---------------
1 file changed, 30 insertions(+), 15 deletions(-)
Index: linux-2.6/kernel/pid.c
===================================================================
--- linux-2.6.orig/kernel/pid.c 2009-09-09 19:06:21.000000000 -0700
+++ linux-2.6/kernel/pid.c 2009-09-09 19:06:25.000000000 -0700
@@ -122,9 +122,35 @@ static void free_pidmap(struct upid *upi
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)
+ kfree(page);
+ else
+ map->page = page;
+ spin_unlock_irq(&pidmap_lock);
+
+ if (unlikely(!map->page))
+ return -ENOMEM;
+
+ return 0;
+}
+
static int alloc_pidmap(struct pid_namespace *pid_ns)
{
int i, offset, max_scan, pid, last = pid_ns->last_pid;
+ int rc;
struct pidmap *map;
pid = last + 1;
@@ -134,21 +160,10 @@ static int alloc_pidmap(struct pid_names
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)
- kfree(page);
- else
- map->page = page;
- spin_unlock_irq(&pidmap_lock);
- if (unlikely(!map->page))
- break;
- }
+ rc = alloc_pidmap_page(map);
+ if (rc)
+ break;
+
if (likely(atomic_read(&map->nr_free))) {
do {
if (!test_and_set_bit(offset, map->page)) {
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