This fixes a bug in madvise() where if you'd try to soft offline a
hugepage via madvise(), while walking the address range you'd end up,
using the wrong page offset due to attempting to get the compound
order of a former but presently not compound page, due to dissolving
the huge page (since c3114a8).
Signed-off-by: Alexandru Moise <00moses.alexander00@xxxxxxxxx>
---
mm/madvise.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/mm/madvise.c b/mm/madvise.c
index 21261ff0466f..25bade36e9ca 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -625,18 +625,26 @@ static int madvise_inject_error(int behavior,
{
struct page *page;
struct zone *zone;
+ unsigned int order;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
- for (; start < end; start += PAGE_SIZE <<
- compound_order(compound_head(page))) {
+
+ for (; start < end; start += PAGE_SIZE << order) {
int ret;
ret = get_user_pages_fast(start, 1, 0, &page);
if (ret != 1)
return ret;
+ /*
+ * When soft offlining hugepages, after migrating the page
+ * we dissolve it, therefore in the second loop "page" will
+ * no longer be a compound page, and order will be 0.
+ */
+ order = compound_order(compound_head(page));
+
if (PageHWPoison(page)) {
put_page(page);
continue;
--
2.14.1
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