[PATCH RT 2/5] zsmalloc: turn that get_cpu_light() into a local_lock()

Steven Rostedt
2016-10-30T16:47:02Z

[-- Attachment #1: 0002-zsmalloc-turn-that-get_cpu_light-into-a-local_lock.patch --]
[-- Type: text/plain, Size: 1838 bytes --]

4.1.35-rt41-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

We might get preempted, grab the same ressource again and then corrupt
the memory.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
mm/zsmalloc.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index e819dffd142c..873d9bdb94fd 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -68,6 +68,7 @@
#include <linux/debugfs.h>
#include <linux/zsmalloc.h>
#include <linux/zpool.h>
+#include <linux/locallock.h>

/*
* This must be power of 2 and greater than of equal to sizeof(link_free).
@@ -398,6 +399,7 @@ static unsigned int get_maxobj_per_zspage(int size, int pages_per_zspage)

/* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
static DEFINE_PER_CPU(struct mapping_area, zs_map_area);
+static DEFINE_LOCAL_IRQ_LOCK(zs_map_area_lock);

static int is_first_page(struct page *page)
{
@@ -1289,7 +1291,7 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle,
class = pool->size_class[class_idx];
off = obj_idx_to_offset(page, obj_idx, class->size);

- area = per_cpu_ptr(&zs_map_area, get_cpu_light());
+ area = &get_locked_var(zs_map_area_lock, zs_map_area);
area->vm_mm = mm;
if (off + class->size <= PAGE_SIZE) {
/* this object is contained entirely within a page */
@@ -1342,7 +1344,7 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle)

__zs_unmap_object(area, pages, off, class->size);
}
- put_cpu_light();
+ put_locked_var(zs_map_area_lock, zs_map_area);
unpin_tag(handle);
}
EXPORT_SYMBOL_GPL(zs_unmap_object);
--
2.9.3