On 02/08/2018 02:34 AM, Michael S. Tsirkin wrote:
On Wed, Feb 07, 2018 at 02:54:30PM +0800, Wei Wang wrote:
In some usages, e.g. virtio-balloon, a kernel module needs to know if
page poisoning is in use. This patch exposes the page_poisoning_enabled
function to kernel modules.
Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
mm/page_poison.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/mm/page_poison.c b/mm/page_poison.c
index e83fd44..c08d02a 100644
--- a/mm/page_poison.c
+++ b/mm/page_poison.c
@@ -30,6 +30,11 @@ bool page_poisoning_enabled(void)
debug_pagealloc_enabled()));
}
+/**
+ * page_poisoning_enabled - check if page poisoning is enabled
+ *
+ * Return true if page poisoning is enabled, or false if not.
+ */
static void poison_page(struct page *page)
{
void *addr = kmap_atomic(page);
@@ -37,6 +42,7 @@ static void poison_page(struct page *page)
memset(addr, PAGE_POISON, PAGE_SIZE);
kunmap_atomic(addr);
}
+EXPORT_SYMBOL_GPL(page_poisoning_enabled);
static void poison_pages(struct page *page, int n)
{
Looks like both the comment and the export are in the wrong place.
Thanks. Will be more careful.
I'm a bit concerned that callers also in fact poke at the
PAGE_POISON - exporting that seems to be more of an accident
as it's only used without page_poisoning.c - it might be
better to have page_poisoning_enabled get u8 * and set it.
PAGE_POISON is a macro defined in the header, why would callers using it
be a concern?
Do you suggest to have:
bool page_poisoning_get(u8 *val)
{
if (page_poisoning_enabled()) {
*val = PAGE_POISON;
return true;
}
return false;
}
EXPORT_SYMBOL_GPL(page_poisoning_get);
Best,
Wei
